Question:
Addressing
Issue needed.
Should we allow or forbid that eadlabel = k and eadlabel = -k correspond to different ead-values? For example, if an (eadlabel, eadvalue) is always critical: Say, eadvalue is an ACE Access Token with eadlabel = -4, always critical. Then we can either: forbid the use of eadlabel = 4 altogether, or allocate an always non-critical EAD to eadlabel = 4, say, eadvalue is "service indication" as in In case 1 we will have some "holes" in the register. One positive integer blocked for each always critical (eadlabel, eadvalue) , one negative blocked for each always non-critical (eadlabel, eadvalue), and 0 cannot be used. (It is not clear to me that there are many always non-critical, but always critical is probably common.) In case 2, we could still have the registration policy that: if an EAD can be either critical or non-critical then two eadlabel with same absolute value should be reserved for it. What is the main risk with case 2? If someone misunderstands or by accident changes sign on an always /non-/critical EAD this results most likely in an error due to wrong eadvalue (like in the example above), but potentially in an unintended EAD message. (Another registration policy could be that the eadvalues corresponding to ead_labels k and -k should have incompatible CDDL so the error is discovered ...) The EAD specification needs anyway to specify what are the processing rules and if you violate those more or less anything could happen. Comments?
BTW, we may want a term for the ordered pair (eadlabel, eadvalue). The term "EAD" or "EAD field" is referring to the message field, which may consist of multiple (eadlabel, eadvalue).
Just seems like overoptimization to me. I would prefer if we follow the model that we agreed on for C509 which is similar to what CoAP Options is using. If you think it is important to use the complete code point space I think it would be better not assign any functionality to the minus sign and register critical and non-critical idenpendently. The original proposal seems to give two different meanings to the minus sign. The minus value is either a criticallity toggle or a completly different EAD.
Introducing the term "EAD item" for (eadlabel, eadvalue)
Edit: Let's include the main points of this PR in -15 as a input to the design team meeting.
I made a proposal. The text now include the concepts "EAD item" and "critical"/"non-critical" EAD item. There is also more details about how applications makes use of EAD: each application registers its own eadlabels eadlabel is a positive integer associated to a particular eadvalue if the application transports different eadvalues then multiple eadlabels need to be registered the application specifies how EAD items are transported in EDHOC messages, a particular EAD item may be transported in multiple messages (i.e. different EADx). I'll merge this into -15 and look forward to comments!
There is a new PR suggesting this. There is no background discussion in the PR . There would be good with some use case. The definition of what critical need and how the recipient handles critical would need a lot of discussion and fine-tuning.The handling of critical extensions in C.509 is to my understanding confusing and problematic. Both in the specification and in implementations.
Please see for background discussion and use cases.
Seems very unclear that the current PR can be the basis for a ECH type mechanism. PR should motivate why it is the basis for an ECH type mechanism or we should have some discussion regarding use cases for a general critical non-critical EAD mechanism. I do not see that follow from .
Having critical/non-critical EAD seems like a reasonable thing in its own, but it is not clear to me that it is a step on the way to a ECH mechanism in EDHOC.
Should we add another column in IANA register? Type: always critical / always non-critical / application determines criticality
If we define such a Type, the following text can be removed from specification and replaced by IANA consideration: "A specification registring a new EAD label MUST describe if the EAD item is always critical, always non-critical, or if it can be decided by the application in the sending endpoint."
I merged which addresses some points raised in this issue. Please review and comment if there is anything missing. The consequences of EDHOC processing of critical / non-critical EAD items is described, but how the security application makes use of this property is left to the associated specification. (In particular, no registration of criticality in the IANA register.)
This is motivated by two considerations, the concerns for clients selecting a hidden service in a protected way (pinging NAME do you have a pointer to your hackathon project), and TLS's encrypted Client Hello (superseding eSNI, encrypted server name indication). The rough situation for either case is that a client has some out-of-band information about the server that includes a public key for encryption (even if the encryption key on its own may be insufficient to authenticate the server). As a straw man proposal (mainly as scaffolding for the "how to enable it" steps later), consider the following: (I bet that reading the will give valuable input for making this complete). To ensure that responders (who are, in their identity selection, the more exposed side) can't be probed for their support of encrypted EAD, encrypted EAD should be marked as "elective" in the sense that a server may ignore it if it does not support it. (It'd still become part of the transcript). If a server receives an EAD it can not decrypt (or which, after decryption, contains nothing valid, eg. because the wrong GE was used), it needs to just continue and pick the CREDR / IDCREDR it would always have picked. AIU we do not yet distinguish between EAD that are elective and those that are critical. I do not know whether we'll even have any "critical" ones (as the peer's lack of action on them should be enough indication that they were unsupported), but if we do distinguish (eg. along the positive/negative number line), encrypted EAD should be optional. This has the upside that initiators that can spare the few bytes can always include some random bytes in the encrypted EAD, and thus ensure that actual users of encrypted EAD do not stand out (or that connections with encrypted EAD would be blocked). It should be a design goal of encrypted EAD that any use of EAD can always be plausibly claimed to just be random bytes added because the specification says one should do that ever now and then. For a practical example, a vulnerable service (say, anything civil rights related) might be operated at the same IP address as a more wide-spread service (say, a large public LwM2M provider). The civil rights service would publish its address together with the public key GE and its service name in DNS records similar to . A client contacting it would start an EDHOC exchange with the public address and encrypt the service name with GEX in the EAD1. The server would respond with credentials for the civil rights service, to which the client then may either present an anonymous (CCS) identity, or (now that it knows it's speaking to the right peer) its own CREDI / IDCREDI. If the CRED sizes are always the same, this exchange should be indistinguishable from an exchange done between an LwM2M client and the LwM2M backend when the client has chosen to send some more garbage bytes. (For application such as eighthalve's, it should be noted that there is probably no need for any further proof of identity inside the EAD1 plaintext: Possession of GE in combination with the suitable plaintext should suffice to open the present alternative server credentials, any secret whose possession is proven in the plaintext part would be exactly as secret as GE, as no attacker without E can obtain the plaintext.). To condense this all into a few actionable points: We should have a code point in eadlabel for "encrypted EAD" data. (We may not even have to specify how it works, that can be specified later or even be guided by the out-of-band information that needs to be present for all of this anyway). That code point either needs to be described explicitly as "MUST ignore if not supported / content not understood" for all of EDHOC from the start, or there needs to be general wording about which ead_labels are to be ignored if unprocessable. We should encourage initiators to send some random garbage there if they can afford it. (A LoRA device certainly can't, a 6lo device probably neigther, but a guard proxy establishing a connection probably can). This is not only to protect initiators that need it, but also to ensure that it is not being blocked, and that responders don't reveal whether they support it.
This has parallels to , which will take some work to pick out in detail.
I'm trying to understand what would need to be changed in EDHOC to support this functionality. The distinction between critical and elective EADs. This seems like a good general construct. Perhaps by designated subsets of labels, e.g. negative or even eablabel are elective. The use of a designated eablabel for encrypted EAD1 seems less general and is somewhat breaking with the mindset that one application is reserving a label and defines the associated processing. Is there a problem with specifying a particular (elective) EAD for this application and associate a policy that it is used by default, with garbage when there is nothing to send? (I couldn't see obfuscating eadlabel really achieved much in practice, but I may have missed something.)
The first, yes. As for the labels, if the application reserves a label and defines the processing, it is showing a passive attacker that it is being used; this may be undesirable. Applications should have some label behind which they can hide the fact that this application is being used; I think it is preferable if that is shared by as many applications as practical (including the "it's really just garbage" application that some hosts may want to run). Whether that requires that they also share an encryption mechanism or not, I am unsure.
NAME at the IETF Hackathon, we put together a working proof of concept for URL Is that what you mean? That's not really related to ECH, but came out of MASQUE.
NAME The three-party setup seems very useful in different settings, so there may be multiple use cases where R receives EAD1 intended for a third party and needs to know that to do with it. Currently eadlabel is filling that function. If we can assume that R by default has designated third party, or sufficient information about the third party is carried in EAD1, then eadlabel could probably be encrypted. (In principle, EAD1 could be a COSEEncrypt0 or any tagged COSE object, with information needed by R in the unprotected header.) So how do we handle the case when there are multiple candidate third parties and you want to hide both the intent and the third party identity? A designated eadlabel is possible (or two, if critical / elective is baked into the label) but I don’t see how this label will be used other applications (so to acheive uncertainty about what is intended) because the co-existence of different candidate applications using EAD1 requires a method for R to distinguish between them. Maybe I'm missing something?
For the attacker to be unable to know which service the user is contacting, it would be important that an initiator receiving the credentials to the wrong service name fails in the same way has an initiator for which verification of the responder signature would fail. Otherwise, an active attacker could test if I intended to use the protected service by xoring the encrypted EAD1 with some random bytes. The responder would always see EAD1 as some random bytes and answer with the unprotected service, and then, if the initiator wanted to talk to the protected service, it will fail after decrypting the message and seeing the wrong service credentials if the initiator want to talk to the unprotected service, it will fail during the verification of the signature as the two transcript will not match. Those two failures should then be indistinguishable from the attacker point of view (even with timing attacks).
At least critical / elective EAD should be included in -15
The critical / elective logic could in principle be implemented in each application. It would be good to provide more use cases to support the case of making this a standardized feature. Clearly there is a benefit with tagging an EAD as "critical" since some operations require the information carried in the EAD to complete, e.g. authorization information from a trusted third party may be required for the Initiator to make any use of the authentication. But what EAD content is not critical? Is the following a good example for elective EAD? A service provider is allowing a variety of devices in its network to authenticate using EDHOC and grants different access rights depending on the capabilities and trustworthiness of the device. Later, the IETF specifies the EAD for remote attestation (see Appendix E). New devices which implements this EAD and appropriately attests to the attestation request carried in the EAD field get certain access which old devices doesn't get. But the old devices should still get basic access. If all EAD were critical then the old device which doesn't understand the new EAD would be forced to discontinue the protocol at the arrival of the remote attestation EAD. If the EAD is elective, then both old and new devices can be supported. Question: With this example in mind, is critical / elective a property of the EAD type, or isn't it rather a boolean set by the application? I can think of another use case where remote attestation is mandatory and it doesn't make sense to define different EADs for these two use cases. (Then we are somehow back at the application specified property. But it may still make sense to have a standardized way of expressing criticality.) Thoughts?
The critical/elective property always needs to be encoded in the message (as an LSB, or as the number's sign) no matter whether criticality is the sender's choice or whether it's part of the registration. From a recent chat I think that registering one number, and then allowing it to be used in positive (elective) or negative (critical) role as by the sender's choice. Application authors would describe in which criticality/-ies it makes sense to use their number, just as they describe in which of the messages it makes sense. (The alternative is to allow registering elective and critical options independently, and that application authors who do need to give the senders a choice of using either would register a pair of options; really would work just as well). Introducing RATS data seems like a very good use case to illustrate EAD examples. (In this particular case I don't know why a sender would insist the attestation to be processed into its network joining). To rephrase the original use cases with recently published terminology, we can refer to . That reference might go with a suggestion that devices that can afford sending a few more bytes should occasionally do so in a grease-style non-critical option, or maybe in a non-critical Encrypted-EAD1 option right away. I'd welcome if ace-ake-autz already defined an EAD field for what could resemble Encrypted-Client-Hello; AIU it currently refers to an older version of EDHOC. It could be updated to place LOCW and ENCID into separate EAD items, and the latter could be more generally defined as "a container for encrypted data which the responder, possibly guided by other EAD1 fields, can use to come up with a suitable IDR". (How encid is then constructed would not be a property of using that particular option, but follow from using the LOCW option). Then, there would be no need for a defined Grease field, as that ENCID field could serve the very same purpose.
Since there seems to be a case for non-critical EAD I made PR . Please review. (Yes, ace-ake-authz needs to be updated, following the closing of this issue.)
I did not read this discussion before now as it did not seem relevant for the base EDHOC protocol. The PR seems quite far from the use case described here. PR described a general critical, non-critical mechanism similar to X.509 extensions while the discussion in this issue is about an ECH type of mechanism..... PR does not seem to be the basis of a good ECH mechanism.... NAME could you have a short presentation at LAKE IETF 114? (edit: fixed Christian's github name)
I think it is clear that PR does not solve the use case outlined here. In particular, the comment from NAME above is not considered as far as I can see. But the point about critical / non-critical (eadlabel, eadvalue) appeared in this discussion and merits to be specified as a general feature.
I think it would be good with longer discussion about ECH type mechanisms in EDHOC. Might be added on later but it could also benefit from being added alrady in the base EDHOC specification. For a use case where the Initiator knows the long term key of the Responder the TLS ECH solution is a quite ugly hack that uses two different keys and an ineficient message flow. The use of a single key as discussed above is an improvement, but the use of a noise XX pattern is not optimal. If you want to design something for the use case where the Initiator knows the long term key of the Responder it makes more sense with noise IK which is used by WireGuard. If the use case where Initiator knows the long term key of the Responder is small the above approach makes sense. If is is big it might make more sense to define new method(s) based on the noise IK pattern.
Could we have a design team meeting or an interim to discuss this issue?
In the use case that the Initiator gets the Responders static public key beforehand The Responder would in this case have a static DH key. The Initiator could use Static DH or a singature.
Perhaps a breakout meeting during/just before IETF 114?
Closing this since NAME agreed that the introduction of critical/non-critical EAD (PR , included in -15) in combination with an example using third party encrypted EAD (as in ace-ake-authz) resolves the issue.

3.8. <del> In order to reduce round trips and the number of messages or to </del> <ins> In order to reduce round trips and the number of messages, or to </ins> simplify processing, external security applications may be integrated into EDHOC by transporting authorization related data in the messages. <del> EDHOC allows opaque external authorization data (EAD) to be sent in each of the four EDHOC messages (EAD_1, EAD_2, EAD_3, EAD_4). </del> <ins> EDHOC allows processing of external authorization data (EAD) to be defined in a separate specification, and sent in dedicated fields of the four EDHOC messages (EAD_1, EAD_2, EAD_3, EAD_4).  EAD is opaque data to EDHOC. </ins> <del> External authorization data is a CBOR sequence (see CBOR) consisting of one or more (ead_label, ead_value) pairs as defined below: </del> <ins> Each EAD field is a CBOR sequence (see CBOR) consisting of one or more EAD items (ead_label, ead_value) as defined below: </ins> A security application using external authorization data need to <del> register an ead_label, specify the ead_value format for each message (see iana-ead), and describe processing and security considerations. </del> <ins> register a positive ead_label and the associated ead_value format for each EAD item it uses (see iana-ead), and describe processing and security considerations.  Each application registers their own EAD items and defines associated operations.  The application may define multiple uses of certain EAD items, e.g., the same EAD item may be used in different EDHOC messages with the same application. An EAD item can be either critical or non-critical, determined by the sign of the ead_label in the transported EAD item included in the EDHOC message.  Using the registered positive value indicates that the EAD item is non-critical.  The corresponding negative value indicates that the EAD item is critical. ead_label = 0 MUST NOT be used. If an endpoint receives a critical EAD item it does not recognize or a critical EAD item that contains information that it cannot process, the EDHOC protocol MUST be discontinued.  A non-critical EAD item can be ignored. The specification registring a new EAD label needs to describe under what conditions the EAD item is critical or non-critical. </ins> The EAD fields of EDHOC must not be used for generic application <del> data.  Examples of the use of EAD is provided in ead-appendix. </del> <ins> data.  Examples of the use of EAD are provided in ead-appendix. </ins> 3.9.


Question:
Addressing
Issue needed.
Should we allow or forbid that eadlabel = k and eadlabel = -k correspond to different ead-values? For example, if an (eadlabel, eadvalue) is always critical: Say, eadvalue is an ACE Access Token with eadlabel = -4, always critical. Then we can either: forbid the use of eadlabel = 4 altogether, or allocate an always non-critical EAD to eadlabel = 4, say, eadvalue is "service indication" as in In case 1 we will have some "holes" in the register. One positive integer blocked for each always critical (eadlabel, eadvalue) , one negative blocked for each always non-critical (eadlabel, eadvalue), and 0 cannot be used. (It is not clear to me that there are many always non-critical, but always critical is probably common.) In case 2, we could still have the registration policy that: if an EAD can be either critical or non-critical then two eadlabel with same absolute value should be reserved for it. What is the main risk with case 2? If someone misunderstands or by accident changes sign on an always /non-/critical EAD this results most likely in an error due to wrong eadvalue (like in the example above), but potentially in an unintended EAD message. (Another registration policy could be that the eadvalues corresponding to ead_labels k and -k should have incompatible CDDL so the error is discovered ...) The EAD specification needs anyway to specify what are the processing rules and if you violate those more or less anything could happen. Comments?
BTW, we may want a term for the ordered pair (eadlabel, eadvalue). The term "EAD" or "EAD field" is referring to the message field, which may consist of multiple (eadlabel, eadvalue).
Just seems like overoptimization to me. I would prefer if we follow the model that we agreed on for C509 which is similar to what CoAP Options is using. If you think it is important to use the complete code point space I think it would be better not assign any functionality to the minus sign and register critical and non-critical idenpendently. The original proposal seems to give two different meanings to the minus sign. The minus value is either a criticallity toggle or a completly different EAD.
Introducing the term "EAD item" for (eadlabel, eadvalue)
Edit: Let's include the main points of this PR in -15 as a input to the design team meeting.
I made a proposal. The text now include the concepts "EAD item" and "critical"/"non-critical" EAD item. There is also more details about how applications makes use of EAD: each application registers its own eadlabels eadlabel is a positive integer associated to a particular eadvalue if the application transports different eadvalues then multiple eadlabels need to be registered the application specifies how EAD items are transported in EDHOC messages, a particular EAD item may be transported in multiple messages (i.e. different EADx). I'll merge this into -15 and look forward to comments!
There is a new PR suggesting this. There is no background discussion in the PR . There would be good with some use case. The definition of what critical need and how the recipient handles critical would need a lot of discussion and fine-tuning.The handling of critical extensions in C.509 is to my understanding confusing and problematic. Both in the specification and in implementations.
Please see for background discussion and use cases.
Seems very unclear that the current PR can be the basis for a ECH type mechanism. PR should motivate why it is the basis for an ECH type mechanism or we should have some discussion regarding use cases for a general critical non-critical EAD mechanism. I do not see that follow from .
Having critical/non-critical EAD seems like a reasonable thing in its own, but it is not clear to me that it is a step on the way to a ECH mechanism in EDHOC.
Should we add another column in IANA register? Type: always critical / always non-critical / application determines criticality
If we define such a Type, the following text can be removed from specification and replaced by IANA consideration: "A specification registring a new EAD label MUST describe if the EAD item is always critical, always non-critical, or if it can be decided by the application in the sending endpoint."
I merged which addresses some points raised in this issue. Please review and comment if there is anything missing. The consequences of EDHOC processing of critical / non-critical EAD items is described, but how the security application makes use of this property is left to the associated specification. (In particular, no registration of criticality in the IANA register.)
This is motivated by two considerations, the concerns for clients selecting a hidden service in a protected way (pinging NAME do you have a pointer to your hackathon project), and TLS's encrypted Client Hello (superseding eSNI, encrypted server name indication). The rough situation for either case is that a client has some out-of-band information about the server that includes a public key for encryption (even if the encryption key on its own may be insufficient to authenticate the server). As a straw man proposal (mainly as scaffolding for the "how to enable it" steps later), consider the following: (I bet that reading the will give valuable input for making this complete). To ensure that responders (who are, in their identity selection, the more exposed side) can't be probed for their support of encrypted EAD, encrypted EAD should be marked as "elective" in the sense that a server may ignore it if it does not support it. (It'd still become part of the transcript). If a server receives an EAD it can not decrypt (or which, after decryption, contains nothing valid, eg. because the wrong GE was used), it needs to just continue and pick the CREDR / IDCREDR it would always have picked. AIU we do not yet distinguish between EAD that are elective and those that are critical. I do not know whether we'll even have any "critical" ones (as the peer's lack of action on them should be enough indication that they were unsupported), but if we do distinguish (eg. along the positive/negative number line), encrypted EAD should be optional. This has the upside that initiators that can spare the few bytes can always include some random bytes in the encrypted EAD, and thus ensure that actual users of encrypted EAD do not stand out (or that connections with encrypted EAD would be blocked). It should be a design goal of encrypted EAD that any use of EAD can always be plausibly claimed to just be random bytes added because the specification says one should do that ever now and then. For a practical example, a vulnerable service (say, anything civil rights related) might be operated at the same IP address as a more wide-spread service (say, a large public LwM2M provider). The civil rights service would publish its address together with the public key GE and its service name in DNS records similar to . A client contacting it would start an EDHOC exchange with the public address and encrypt the service name with GEX in the EAD1. The server would respond with credentials for the civil rights service, to which the client then may either present an anonymous (CCS) identity, or (now that it knows it's speaking to the right peer) its own CREDI / IDCREDI. If the CRED sizes are always the same, this exchange should be indistinguishable from an exchange done between an LwM2M client and the LwM2M backend when the client has chosen to send some more garbage bytes. (For application such as eighthalve's, it should be noted that there is probably no need for any further proof of identity inside the EAD1 plaintext: Possession of GE in combination with the suitable plaintext should suffice to open the present alternative server credentials, any secret whose possession is proven in the plaintext part would be exactly as secret as GE, as no attacker without E can obtain the plaintext.). To condense this all into a few actionable points: We should have a code point in eadlabel for "encrypted EAD" data. (We may not even have to specify how it works, that can be specified later or even be guided by the out-of-band information that needs to be present for all of this anyway). That code point either needs to be described explicitly as "MUST ignore if not supported / content not understood" for all of EDHOC from the start, or there needs to be general wording about which ead_labels are to be ignored if unprocessable. We should encourage initiators to send some random garbage there if they can afford it. (A LoRA device certainly can't, a 6lo device probably neigther, but a guard proxy establishing a connection probably can). This is not only to protect initiators that need it, but also to ensure that it is not being blocked, and that responders don't reveal whether they support it.
This has parallels to , which will take some work to pick out in detail.
I'm trying to understand what would need to be changed in EDHOC to support this functionality. The distinction between critical and elective EADs. This seems like a good general construct. Perhaps by designated subsets of labels, e.g. negative or even eablabel are elective. The use of a designated eablabel for encrypted EAD1 seems less general and is somewhat breaking with the mindset that one application is reserving a label and defines the associated processing. Is there a problem with specifying a particular (elective) EAD for this application and associate a policy that it is used by default, with garbage when there is nothing to send? (I couldn't see obfuscating eadlabel really achieved much in practice, but I may have missed something.)
The first, yes. As for the labels, if the application reserves a label and defines the processing, it is showing a passive attacker that it is being used; this may be undesirable. Applications should have some label behind which they can hide the fact that this application is being used; I think it is preferable if that is shared by as many applications as practical (including the "it's really just garbage" application that some hosts may want to run). Whether that requires that they also share an encryption mechanism or not, I am unsure.
NAME at the IETF Hackathon, we put together a working proof of concept for URL Is that what you mean? That's not really related to ECH, but came out of MASQUE.
NAME The three-party setup seems very useful in different settings, so there may be multiple use cases where R receives EAD1 intended for a third party and needs to know that to do with it. Currently eadlabel is filling that function. If we can assume that R by default has designated third party, or sufficient information about the third party is carried in EAD1, then eadlabel could probably be encrypted. (In principle, EAD1 could be a COSEEncrypt0 or any tagged COSE object, with information needed by R in the unprotected header.) So how do we handle the case when there are multiple candidate third parties and you want to hide both the intent and the third party identity? A designated eadlabel is possible (or two, if critical / elective is baked into the label) but I don’t see how this label will be used other applications (so to acheive uncertainty about what is intended) because the co-existence of different candidate applications using EAD1 requires a method for R to distinguish between them. Maybe I'm missing something?
For the attacker to be unable to know which service the user is contacting, it would be important that an initiator receiving the credentials to the wrong service name fails in the same way has an initiator for which verification of the responder signature would fail. Otherwise, an active attacker could test if I intended to use the protected service by xoring the encrypted EAD1 with some random bytes. The responder would always see EAD1 as some random bytes and answer with the unprotected service, and then, if the initiator wanted to talk to the protected service, it will fail after decrypting the message and seeing the wrong service credentials if the initiator want to talk to the unprotected service, it will fail during the verification of the signature as the two transcript will not match. Those two failures should then be indistinguishable from the attacker point of view (even with timing attacks).
At least critical / elective EAD should be included in -15
The critical / elective logic could in principle be implemented in each application. It would be good to provide more use cases to support the case of making this a standardized feature. Clearly there is a benefit with tagging an EAD as "critical" since some operations require the information carried in the EAD to complete, e.g. authorization information from a trusted third party may be required for the Initiator to make any use of the authentication. But what EAD content is not critical? Is the following a good example for elective EAD? A service provider is allowing a variety of devices in its network to authenticate using EDHOC and grants different access rights depending on the capabilities and trustworthiness of the device. Later, the IETF specifies the EAD for remote attestation (see Appendix E). New devices which implements this EAD and appropriately attests to the attestation request carried in the EAD field get certain access which old devices doesn't get. But the old devices should still get basic access. If all EAD were critical then the old device which doesn't understand the new EAD would be forced to discontinue the protocol at the arrival of the remote attestation EAD. If the EAD is elective, then both old and new devices can be supported. Question: With this example in mind, is critical / elective a property of the EAD type, or isn't it rather a boolean set by the application? I can think of another use case where remote attestation is mandatory and it doesn't make sense to define different EADs for these two use cases. (Then we are somehow back at the application specified property. But it may still make sense to have a standardized way of expressing criticality.) Thoughts?
The critical/elective property always needs to be encoded in the message (as an LSB, or as the number's sign) no matter whether criticality is the sender's choice or whether it's part of the registration. From a recent chat I think that registering one number, and then allowing it to be used in positive (elective) or negative (critical) role as by the sender's choice. Application authors would describe in which criticality/-ies it makes sense to use their number, just as they describe in which of the messages it makes sense. (The alternative is to allow registering elective and critical options independently, and that application authors who do need to give the senders a choice of using either would register a pair of options; really would work just as well). Introducing RATS data seems like a very good use case to illustrate EAD examples. (In this particular case I don't know why a sender would insist the attestation to be processed into its network joining). To rephrase the original use cases with recently published terminology, we can refer to . That reference might go with a suggestion that devices that can afford sending a few more bytes should occasionally do so in a grease-style non-critical option, or maybe in a non-critical Encrypted-EAD1 option right away. I'd welcome if ace-ake-autz already defined an EAD field for what could resemble Encrypted-Client-Hello; AIU it currently refers to an older version of EDHOC. It could be updated to place LOCW and ENCID into separate EAD items, and the latter could be more generally defined as "a container for encrypted data which the responder, possibly guided by other EAD1 fields, can use to come up with a suitable IDR". (How encid is then constructed would not be a property of using that particular option, but follow from using the LOCW option). Then, there would be no need for a defined Grease field, as that ENCID field could serve the very same purpose.
Since there seems to be a case for non-critical EAD I made PR . Please review. (Yes, ace-ake-authz needs to be updated, following the closing of this issue.)
I did not read this discussion before now as it did not seem relevant for the base EDHOC protocol. The PR seems quite far from the use case described here. PR described a general critical, non-critical mechanism similar to X.509 extensions while the discussion in this issue is about an ECH type of mechanism..... PR does not seem to be the basis of a good ECH mechanism.... NAME could you have a short presentation at LAKE IETF 114? (edit: fixed Christian's github name)
I think it is clear that PR does not solve the use case outlined here. In particular, the comment from NAME above is not considered as far as I can see. But the point about critical / non-critical (eadlabel, eadvalue) appeared in this discussion and merits to be specified as a general feature.
I think it would be good with longer discussion about ECH type mechanisms in EDHOC. Might be added on later but it could also benefit from being added alrady in the base EDHOC specification. For a use case where the Initiator knows the long term key of the Responder the TLS ECH solution is a quite ugly hack that uses two different keys and an ineficient message flow. The use of a single key as discussed above is an improvement, but the use of a noise XX pattern is not optimal. If you want to design something for the use case where the Initiator knows the long term key of the Responder it makes more sense with noise IK which is used by WireGuard. If the use case where Initiator knows the long term key of the Responder is small the above approach makes sense. If is is big it might make more sense to define new method(s) based on the noise IK pattern.
Could we have a design team meeting or an interim to discuss this issue?
In the use case that the Initiator gets the Responders static public key beforehand The Responder would in this case have a static DH key. The Initiator could use Static DH or a singature.
Perhaps a breakout meeting during/just before IETF 114?
Closing this since NAME agreed that the introduction of critical/non-critical EAD (PR , included in -15) in combination with an example using third party encrypted EAD (as in ace-ake-authz) resolves the issue.

Authorization Data" under the new group name "Ephemeral Diffie- Hellman Over COSE (EDHOC)".  The registration procedure is "Specification Required".  The columns of the registry are Label, <del> Message, Description, and Reference, where Label is an integer and the other columns are text strings. </del> <ins> Description, and Reference, where Label is a positive integer and the other columns are text strings. </ins> 9.6.


Question:
URL I have been reading v17 and sent some comments to the authors, that I summarize here: 1) - Regarding RPK, previous versions of the document had a more detailed explanation about RPK. For example, in version v06 you had "The Initiator and the Responder MAY use different types of credentials, e.g. one uses an RPK and the other uses a public key certificate.” So RPK is included as part of the definition of authentication credential. However, v17 may have a different meaning since it seems “credentials" is defined as follows: "EDHOC relies on COSE for identification of credentials (see Section 3.5.3), for example X.509 certificates [RFC5280], C509 certificates [I-D.ietf-cose-cbor-encoded-cert], CWTs [RFC8392] and CWT Claims Sets (CCS) [RFC8392]. When the identified credential is a chain or a bag, the authentication credential CRED_x is just the end entity X.509 or C509 certificate / CWT. I assume RPK is also an authentication credential and this should be included in this text. A clarification would be worthy. 2) I assume it is possible that any two IoT devices can act as initiator but also as a responder, even between same two peers. It is the application which decides when to start EDHOC (initiator) in a particular case, correct? 3) It seems the EDHOC does not define any exchange for the key update (some sort of rekey). It seems an application at some point exchange some messages as "some event that triggered the key update.” Then the application call to EDHOC-KeyUpdate function to get a new PRK. Am I right? I am asking because looking at IKEv2, for example, and for the rekey, an exchange is required. Although it would add a little bit more complexity, wouldn’t it be sensical that EDHOC defines a 1 RTT to exchange a couple of nonces for the rekeying. Moreover, this function is defined in an Appendix. Is it mandatory to implement?
Yes. The document should talk about RPK a bit more as that is term that people might search for. Should be explained that CWT is the format EDHOC uses for raw public keys (RPK). Hi all: I have been reading v17 and sent some comments to the authors, that I summarize here: 1) - Regarding RPK, previous versions of the document had a more detailed explanation about RPK. For example, in version v06 you had "The Initiator and the Responder MAY use different types of credentials, e.g. one uses an RPK and the other uses a public key certificate.” So RPK is included as part of the definition of authentication credential. However, v17 may have a different meaning since it seems “credentials" is defined as follows: "EDHOC relies on COSE for identification of credentials (see Section 3.5.3), for example X.509 certificates [RFC5280], C509 certificates [I-D.ietf-cose-cbor-encoded-cert], CWTs [RFC8392] and CWT Claims Sets (CCS) [RFC8392]. When the identified credential is a chain or a bag, the authentication credential CRED_x is just the end entity X.509 or C509 certificate / CWT. I assume RPK is also an authentication credential and this should be included in this text. A clarification would be worthy. 2) I assume it is possible that any two IoT devices can act as initiator but also as a responder, even between same two peers. It is the application which decides when to start EDHOC (initiator) in a particular case, correct? 3) It seems the EDHOC does not define any exchange for the key update (some sort of rekey). It seems an application at some point exchange some messages as "some event that triggered the key update.” Then the application call to EDHOC-KeyUpdate function to get a new PRK. Am I right? I am asking because looking at IKEv2, for example, and for the rekey, an exchange is required. Although it would add a little bit more complexity, wouldn’t it be sensical that EDHOC defines a 1 RTT to exchange a couple of nonces for the rekeying. Moreover, this function is defined in an Appendix. Is it mandatory to implement? Beyond these clarifications, I think the document is ready. Best Regards. Rafa Marin-Lopez, PhD Dept. Information and Communications Engineering (DIIC) Faculty of Computer Science-University of Murcia 30100 Murcia - Spain Telf: +34868888501 Fax: +34868884151 e-mail: EMAIL

3.1. The EDHOC protocol consists of three mandatory messages (message_1, <del> message_2, message_3) between Initiator and Responder, an optional fourth message (message_4), and an error message.  All EDHOC messages are CBOR Sequences RFC8742, and are deterministically encoded. fig- flow illustrates an EDHOC message flow with the optional fourth message as well as the content of each message.  The protocol </del> <ins> message_2, message_3) between an Initiator and a Responder, an optional fourth message (message_4), and an error message.  The roles have slightly different security properties which should be considered when the roles are assigned, see sec-prop.  All EDHOC messages are CBOR Sequences RFC8742, and are deterministically encoded. fig-flow illustrates an EDHOC message flow with the optional fourth message as well as the content of each message.  The protocol </ins> elements in the figure are introduced in overview and asym.  Message formatting and processing are specified in asym and error.


Question:
URL I have been reading v17 and sent some comments to the authors, that I summarize here: 1) - Regarding RPK, previous versions of the document had a more detailed explanation about RPK. For example, in version v06 you had "The Initiator and the Responder MAY use different types of credentials, e.g. one uses an RPK and the other uses a public key certificate.” So RPK is included as part of the definition of authentication credential. However, v17 may have a different meaning since it seems “credentials" is defined as follows: "EDHOC relies on COSE for identification of credentials (see Section 3.5.3), for example X.509 certificates [RFC5280], C509 certificates [I-D.ietf-cose-cbor-encoded-cert], CWTs [RFC8392] and CWT Claims Sets (CCS) [RFC8392]. When the identified credential is a chain or a bag, the authentication credential CRED_x is just the end entity X.509 or C509 certificate / CWT. I assume RPK is also an authentication credential and this should be included in this text. A clarification would be worthy. 2) I assume it is possible that any two IoT devices can act as initiator but also as a responder, even between same two peers. It is the application which decides when to start EDHOC (initiator) in a particular case, correct? 3) It seems the EDHOC does not define any exchange for the key update (some sort of rekey). It seems an application at some point exchange some messages as "some event that triggered the key update.” Then the application call to EDHOC-KeyUpdate function to get a new PRK. Am I right? I am asking because looking at IKEv2, for example, and for the rekey, an exchange is required. Although it would add a little bit more complexity, wouldn’t it be sensical that EDHOC defines a 1 RTT to exchange a couple of nonces for the rekeying. Moreover, this function is defined in an Appendix. Is it mandatory to implement?
Yes. The document should talk about RPK a bit more as that is term that people might search for. Should be explained that CWT is the format EDHOC uses for raw public keys (RPK). Hi all: I have been reading v17 and sent some comments to the authors, that I summarize here: 1) - Regarding RPK, previous versions of the document had a more detailed explanation about RPK. For example, in version v06 you had "The Initiator and the Responder MAY use different types of credentials, e.g. one uses an RPK and the other uses a public key certificate.” So RPK is included as part of the definition of authentication credential. However, v17 may have a different meaning since it seems “credentials" is defined as follows: "EDHOC relies on COSE for identification of credentials (see Section 3.5.3), for example X.509 certificates [RFC5280], C509 certificates [I-D.ietf-cose-cbor-encoded-cert], CWTs [RFC8392] and CWT Claims Sets (CCS) [RFC8392]. When the identified credential is a chain or a bag, the authentication credential CRED_x is just the end entity X.509 or C509 certificate / CWT. I assume RPK is also an authentication credential and this should be included in this text. A clarification would be worthy. 2) I assume it is possible that any two IoT devices can act as initiator but also as a responder, even between same two peers. It is the application which decides when to start EDHOC (initiator) in a particular case, correct? 3) It seems the EDHOC does not define any exchange for the key update (some sort of rekey). It seems an application at some point exchange some messages as "some event that triggered the key update.” Then the application call to EDHOC-KeyUpdate function to get a new PRK. Am I right? I am asking because looking at IKEv2, for example, and for the rekey, an exchange is required. Although it would add a little bit more complexity, wouldn’t it be sensical that EDHOC defines a 1 RTT to exchange a couple of nonces for the rekeying. Moreover, this function is defined in an Appendix. Is it mandatory to implement? Beyond these clarifications, I think the document is ready. Best Regards. Rafa Marin-Lopez, PhD Dept. Information and Communications Engineering (DIIC) Faculty of Computer Science-University of Murcia 30100 Murcia - Spain Telf: +34868888501 Fax: +34868884151 e-mail: EMAIL

respectively, and the public authentication keys are denoted G_I and G_R, respectively. <del> For X.509 certificates the authentication key is represented with a </del> <ins> For X.509 certificates the authentication key is represented by a </ins> SubjectPublicKeyInfo field.  For CWT and CCS (see auth-cred)) the <del> authentication key is represented with a 'cnf' claim RFC8747 containing a COSE_Key RFC9052. </del> <ins> authentication key is represented by a 'cnf' claim RFC8747 containing a COSE_Key RFC9052.  In EDHOC, a raw public key (RPK) is an authentication key encoded as a COSE_Key wrapped in a CCS. </ins> 3.5.2. The authentication credentials, CRED_I and CRED_R, contain the public authentication key of the Initiator and the Responder, respectively. <ins> The authentication credential typically also contains other parameters that needs to be verified by the application, see auth- validation, and in particular information about the identity ("subject") of the endpoint to prevent misbinding attacks, see identities. </ins> EDHOC relies on COSE for identification of credentials (see id_cred), for example X.509 certificates RFC5280, C509 certificates I-D.ietf- cose-cbor-encoded-cert, CWTs RFC8392 and CWT Claims Sets (CCS) RFC8392.  When the identified credential is a chain or a bag, the authentication credential CRED_x is just the end entity X.509 or C509 <del> certificate / CWT. </del> <ins> certificate / CWT.  The Initiator and the Responder MAY use different types of authentication credentials, e.g., one uses an RPK and the other uses a public key certificate. </ins> Since CRED_R is used in the integrity verification, see asym- msg2-proc, it needs to be specified such that it is identical when


Question:
URL I have been reading v17 and sent some comments to the authors, that I summarize here: 1) - Regarding RPK, previous versions of the document had a more detailed explanation about RPK. For example, in version v06 you had "The Initiator and the Responder MAY use different types of credentials, e.g. one uses an RPK and the other uses a public key certificate.” So RPK is included as part of the definition of authentication credential. However, v17 may have a different meaning since it seems “credentials" is defined as follows: "EDHOC relies on COSE for identification of credentials (see Section 3.5.3), for example X.509 certificates [RFC5280], C509 certificates [I-D.ietf-cose-cbor-encoded-cert], CWTs [RFC8392] and CWT Claims Sets (CCS) [RFC8392]. When the identified credential is a chain or a bag, the authentication credential CRED_x is just the end entity X.509 or C509 certificate / CWT. I assume RPK is also an authentication credential and this should be included in this text. A clarification would be worthy. 2) I assume it is possible that any two IoT devices can act as initiator but also as a responder, even between same two peers. It is the application which decides when to start EDHOC (initiator) in a particular case, correct? 3) It seems the EDHOC does not define any exchange for the key update (some sort of rekey). It seems an application at some point exchange some messages as "some event that triggered the key update.” Then the application call to EDHOC-KeyUpdate function to get a new PRK. Am I right? I am asking because looking at IKEv2, for example, and for the rekey, an exchange is required. Although it would add a little bit more complexity, wouldn’t it be sensical that EDHOC defines a 1 RTT to exchange a couple of nonces for the rekeying. Moreover, this function is defined in an Appendix. Is it mandatory to implement?
Yes. The document should talk about RPK a bit more as that is term that people might search for. Should be explained that CWT is the format EDHOC uses for raw public keys (RPK). Hi all: I have been reading v17 and sent some comments to the authors, that I summarize here: 1) - Regarding RPK, previous versions of the document had a more detailed explanation about RPK. For example, in version v06 you had "The Initiator and the Responder MAY use different types of credentials, e.g. one uses an RPK and the other uses a public key certificate.” So RPK is included as part of the definition of authentication credential. However, v17 may have a different meaning since it seems “credentials" is defined as follows: "EDHOC relies on COSE for identification of credentials (see Section 3.5.3), for example X.509 certificates [RFC5280], C509 certificates [I-D.ietf-cose-cbor-encoded-cert], CWTs [RFC8392] and CWT Claims Sets (CCS) [RFC8392]. When the identified credential is a chain or a bag, the authentication credential CRED_x is just the end entity X.509 or C509 certificate / CWT. I assume RPK is also an authentication credential and this should be included in this text. A clarification would be worthy. 2) I assume it is possible that any two IoT devices can act as initiator but also as a responder, even between same two peers. It is the application which decides when to start EDHOC (initiator) in a particular case, correct? 3) It seems the EDHOC does not define any exchange for the key update (some sort of rekey). It seems an application at some point exchange some messages as "some event that triggered the key update.” Then the application call to EDHOC-KeyUpdate function to get a new PRK. Am I right? I am asking because looking at IKEv2, for example, and for the rekey, an exchange is required. Although it would add a little bit more complexity, wouldn’t it be sensical that EDHOC defines a 1 RTT to exchange a couple of nonces for the rekeying. Moreover, this function is defined in an Appendix. Is it mandatory to implement? Beyond these clarifications, I think the document is ready. Best Regards. Rafa Marin-Lopez, PhD Dept. Information and Communications Engineering (DIIC) Faculty of Computer Science-University of Murcia 30100 Murcia - Spain Telf: +34868888501 Fax: +34868884151 e-mail: EMAIL

SHALL be the C509Certificate I-D.ietf-cose-cbor-encoded-cert. When the authentication credential is a CWT including a COSE_Key, <del> then CRED_x SHALL be the untagged CWT. </del> <ins> CRED_x SHALL be the untagged CWT. </ins> When the authentication credential includes a COSE_Key but is not <del> in a CWT, CRED_x SHALL be an untagged CCS. </del> <ins> in a CWT, CRED_x SHALL be an untagged CCS.  This is how RPKs are encoded, see fig-ccs for an example. </ins> <del> Naked COSE_Keys are thus dressed as CCS when used in EDHOC, which is done by prefixing the COSE_Key with 0xA108A101. </del> <ins> Naked COSE_Keys are thus dressed as CCS when used in EDHOC, in its simplest form by prefixing the COSE_Key with 0xA108A101 (a map with a 'cnf' claim).  In that case the resulting authentication credential contains no other identity than the public key itself, see identities. </ins> An example of a CRED_x is shown below:


Question:
URL I have been reading v17 and sent some comments to the authors, that I summarize here: 1) - Regarding RPK, previous versions of the document had a more detailed explanation about RPK. For example, in version v06 you had "The Initiator and the Responder MAY use different types of credentials, e.g. one uses an RPK and the other uses a public key certificate.” So RPK is included as part of the definition of authentication credential. However, v17 may have a different meaning since it seems “credentials" is defined as follows: "EDHOC relies on COSE for identification of credentials (see Section 3.5.3), for example X.509 certificates [RFC5280], C509 certificates [I-D.ietf-cose-cbor-encoded-cert], CWTs [RFC8392] and CWT Claims Sets (CCS) [RFC8392]. When the identified credential is a chain or a bag, the authentication credential CRED_x is just the end entity X.509 or C509 certificate / CWT. I assume RPK is also an authentication credential and this should be included in this text. A clarification would be worthy. 2) I assume it is possible that any two IoT devices can act as initiator but also as a responder, even between same two peers. It is the application which decides when to start EDHOC (initiator) in a particular case, correct? 3) It seems the EDHOC does not define any exchange for the key update (some sort of rekey). It seems an application at some point exchange some messages as "some event that triggered the key update.” Then the application call to EDHOC-KeyUpdate function to get a new PRK. Am I right? I am asking because looking at IKEv2, for example, and for the rekey, an exchange is required. Although it would add a little bit more complexity, wouldn’t it be sensical that EDHOC defines a 1 RTT to exchange a couple of nonces for the rekeying. Moreover, this function is defined in an Appendix. Is it mandatory to implement?
Yes. The document should talk about RPK a bit more as that is term that people might search for. Should be explained that CWT is the format EDHOC uses for raw public keys (RPK). Hi all: I have been reading v17 and sent some comments to the authors, that I summarize here: 1) - Regarding RPK, previous versions of the document had a more detailed explanation about RPK. For example, in version v06 you had "The Initiator and the Responder MAY use different types of credentials, e.g. one uses an RPK and the other uses a public key certificate.” So RPK is included as part of the definition of authentication credential. However, v17 may have a different meaning since it seems “credentials" is defined as follows: "EDHOC relies on COSE for identification of credentials (see Section 3.5.3), for example X.509 certificates [RFC5280], C509 certificates [I-D.ietf-cose-cbor-encoded-cert], CWTs [RFC8392] and CWT Claims Sets (CCS) [RFC8392]. When the identified credential is a chain or a bag, the authentication credential CRED_x is just the end entity X.509 or C509 certificate / CWT. I assume RPK is also an authentication credential and this should be included in this text. A clarification would be worthy. 2) I assume it is possible that any two IoT devices can act as initiator but also as a responder, even between same two peers. It is the application which decides when to start EDHOC (initiator) in a particular case, correct? 3) It seems the EDHOC does not define any exchange for the key update (some sort of rekey). It seems an application at some point exchange some messages as "some event that triggered the key update.” Then the application call to EDHOC-KeyUpdate function to get a new PRK. Am I right? I am asking because looking at IKEv2, for example, and for the rekey, an exchange is required. Although it would add a little bit more complexity, wouldn’t it be sensical that EDHOC defines a 1 RTT to exchange a couple of nonces for the rekeying. Moreover, this function is defined in an Appendix. Is it mandatory to implement? Beyond these clarifications, I think the document is ready. Best Regards. Rafa Marin-Lopez, PhD Dept. Information and Communications Engineering (DIIC) Faculty of Computer Science-University of Murcia 30100 Murcia - Spain Telf: +34868888501 Fax: +34868884151 e-mail: EMAIL

protocol execution (specifically, cipher suite, see cs) but other parameters are only communicated and may not be negotiated (e.g., which authentication method is used, see method).  Yet other <del> parameters need to be known out-of-band. </del> <ins> parameters need to be known out-of-band.  The application decides which endpoint is Initiator and which is Responder. </ins> The purpose of an application profile is to describe the intended use of EDHOC to allow for the relevant processing and verifications to be


Question:
I strongly think that all 10 EDHOC-KDF should be in the same table The text about maclengthx need to use the defined term hash_length
I made one commit for review.

Transport of external authorization data. EDHOC is designed to encrypt and integrity protect as much <del> information as possible.  Symmetric keys and random material derived using EDHOC_KDF are derived with as much previous information as possible, see fig-edhoc-kdf.  EDHOC is furthermore designed to be as compact and lightweight as possible, in terms of message sizes, </del> <ins> information as possible.  Symmetric keys and random material used in EDHOC are derived using EDHOC_KDF with as much previous information as possible, see fig-edhoc-kdf.  EDHOC is furthermore designed to be as compact and lightweight as possible, in terms of message sizes, </ins> processing, and the ability to reuse already existing CBOR, COSE, and CoAP libraries.  Like in (D)TLS, authentication is the responsibility of the application.  EDHOC identifies (and optionally transports)


Question:
I strongly think that all 10 EDHOC-KDF should be in the same table The text about maclengthx need to use the defined term hash_length
I made one commit for review.

length, the output length in bits. <del> fig-edhoc-kdf lists derivations made with EDHOC_KDF during message processing, where </del> <ins> fig-edhoc-kdf lists derivations made with EDHOC_KDF, where </ins> hash_length - length of output size of the EDHOC hash algorithm of the selected cipher suite


Question:
I strongly think that all 10 EDHOC-KDF should be in the same table The text about maclengthx need to use the defined term hash_length
I made one commit for review.

4.1.3. <del> The pseudorandom key PRK_out, derived as shown in fig-edhoc-kdf is </del> <ins> The pseudorandom key PRK_out, derived as shown in fig-edhoc-kdf, is </ins> the output session key of a successful EDHOC exchange. <del> Keys for applications are derived using EDHOC_Exporter from PRK_exporter (see exporter) which in turn is derived from PRK_out. For the purpose of generating application keys, it is sufficient to store PRK_out or PRK_exporter.  (Note that the word "store" used here does not imply that the application has access to the plaintext PRK_out since that may be reserved for code within a Trusted Execution Environment, see impl-cons). </del> <ins> Keys for applications are derived using EDHOC_Exporter (see exporter) from PRK_exporter, which in turn is derived from PRK_out as shown in fig-edhoc-kdf.  For the purpose of generating application keys, it is sufficient to store PRK_out or PRK_exporter.  (Note that the word "store" used here does not imply that the application has access to the plaintext PRK_out since that may be reserved for code within a Trusted Execution Environment, see impl-cons). </ins> 4.2. This section defines EDHOC_Exporter in terms of EDHOC_KDF and <del> PRK_out.  A key update function is defined in keyupdate. </del> <ins> PRK_exporter.  A key update function is defined in keyupdate. </ins> 4.2.1.


Question:
I strongly think that all 10 EDHOC-KDF should be in the same table The text about maclengthx need to use the defined term hash_length
I made one commit for review.

length is a uint defined by the application <del> PRK_exporter is derived from PRK_out: where hash_length denotes the output size in bytes of the EDHOC hash algorithm of the selected cipher suite. </del> The (exporter_label, context) pair used in EDHOC_Exporter must be unique, i.e., an (exporter_label, context) MUST NOT be used for two different purposes.  However an application can re-derive the same


Question:
I strongly think that all 10 EDHOC-KDF should be in the same table The text about maclengthx need to use the defined term hash_length
I made one commit for review.

(method equals 1 or 3), then mac_length_2 is the EDHOC MAC length of the selected cipher suite.  If the Responder authenticates with a signature key (method equals 0 or 2), then <del> mac_length_2 is equal to the output size of the EDHOC hash algorithm of the selected cipher suite. </del> <ins> mac_length_2 is equal to hash_length. </ins> ID_CRED_R - identifier to facilitate the retrieval of CRED_R, see


Question:
I strongly think that all 10 EDHOC-KDF should be in the same table The text about maclengthx need to use the defined term hash_length
I made one commit for review.

(method equals 2 or 3), then mac_length_3 is the EDHOC MAC length of the selected cipher suite.  If the Initiator authenticates with a signature key (method equals 0 or 1), then <del> mac_length_3 is equal to the output size of the EDHOC hash algorithm of the selected cipher suite. </del> <ins> mac_length_3 is equal to hash_length. </ins> ID_CRED_I - identifier to facilitate the retrieval of CRED_I, see


Question:
This builds on .
Summary: use a high-entropy PSK with DH, otherwise, with a low-entropy PSK, use a PAKE. Reference appendix with security properties from NAME

4. <del> Applications MUST use external PSKs that adhere to the following requirements: Each PSK MUST be derived from at least 128 of entropy and MUST be at least 128-bits long unless the TLS handshake is being used with a separate key establishment mechanism such as a Diffie-Hellman exchange.  This recommendation protects against passive attacks using exhaustive search of the PSK. </del> <ins> Applications MUST adhere to the following requirements for external PSKs: Each PSK SHOULD be derived from at least 128 bits of entropy, MUST be at least 128 bits long, and SHOULD be combined with a DH exchange for forward secrecy.  Low entropy PSKs, i.e., those derived from less than 128 bits of entropy, MUST be combined with a Password Authenticated Key Exchange (PAKE) mechanism. </ins> Each PSK MUST NOT be shared between with more than two logical nodes.  As a result, an agent that acts as both a client and a


Question:
FIxed up: some nits on recommendations. I think the wording was a bit off on low entropy PSKs, so I lifted from ekrs text from earlier in the draft. some of the stack interface stuff on hints is not valid for TLS1.3 (hints are TLS1.2 and earlier), so removed it. Some prelim text on collisions. For completeness, will take a look at gnutls and wolfssl order too. Note, even with the OpenSSL callback sequence, the application still does not know if there is a collision...
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violated, then the security properties of TLS are severely weakened. As discussed in use-cases, there are use cases where it is desirable <del> for multiple clients or multiple servers share a PSK.  If this is </del> <ins> for multiple clients or multiple servers to share a PSK.  If this is </ins> done naively by having all members share a common key, then TLS only authenticates the entire group, and the security of the overall system is inherently rather brittle.  There are a number of obvious


Question:
FIxed up: some nits on recommendations. I think the wording was a bit off on low entropy PSKs, so I lifted from ekrs text from earlier in the draft. some of the stack interface stuff on hints is not valid for TLS1.3 (hints are TLS1.2 and earlier), so removed it. Some prelim text on collisions. For completeness, will take a look at gnutls and wolfssl order too. Note, even with the OpenSSL callback sequence, the application still does not know if there is a collision...
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appearing in cleartext in a ClientHello.  As a result, a passive adversary can link two or more connections together that use the same external PSK on the wire.  Applications should take precautions when <del> using external PSKs if these risks. </del> <ins> using external PSKs to mitigate these risks. </ins> In addition to linkability in the network, external PSKs are intrinsically linkable by PSK receivers.  Specifically, servers can


Question:
FIxed up: some nits on recommendations. I think the wording was a bit off on low entropy PSKs, so I lifted from ekrs text from earlier in the draft. some of the stack interface stuff on hints is not valid for TLS1.3 (hints are TLS1.2 and earlier), so removed it. Some prelim text on collisions. For completeness, will take a look at gnutls and wolfssl order too. Note, even with the OpenSSL callback sequence, the application still does not know if there is a collision...
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constrained UI.  Moreover, PSK production lacks guidance unlike user passwords. <del> Some devices are provisioned PSKs via an out-of-band, cloud-based </del> <ins> Some devices provision PSKs via an out-of-band, cloud-based </ins> syncing protocol. Some secrets may be baked into or hardware or software device


Question:
FIxed up: some nits on recommendations. I think the wording was a bit off on low entropy PSKs, so I lifted from ekrs text from earlier in the draft. some of the stack interface stuff on hints is not valid for TLS1.3 (hints are TLS1.2 and earlier), so removed it. Some prelim text on collisions. For completeness, will take a look at gnutls and wolfssl order too. Note, even with the OpenSSL callback sequence, the application still does not know if there is a collision...
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Each PSK SHOULD be derived from at least 128 bits of entropy, MUST be at least 128 bits long, and SHOULD be combined with a DH <del> exchange for forward secrecy.  Low entropy PSKs, i.e., those derived from less than 128 bits of entropy, MUST be combined with a Password Authenticated Key Exchange (PAKE) mechanism. </del> <ins> exchange for forward secrecy.  As discussed in sec-properties, low entropy PSKs, i.e., those derived from less than 128 bits of entropy, are subject to attack and SHOULD be avoided.  Low entropy keys are only secure against active attack if a Password Authenticated Key Exchange (PAKE) is used with TLS. </ins> Each PSK MUST NOT be shared between with more than two logical nodes.  As a result, an agent that acts as both a client and a


Question:
FIxed up: some nits on recommendations. I think the wording was a bit off on low entropy PSKs, so I lifted from ekrs text from earlier in the draft. some of the stack interface stuff on hints is not valid for TLS1.3 (hints are TLS1.2 and earlier), so removed it. Some prelim text on collisions. For completeness, will take a look at gnutls and wolfssl order too. Note, even with the OpenSSL callback sequence, the application still does not know if there is a collision...
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6.1. <del> Most major TLS implementations support external PSKs.  And all have a common interface that applications may use when supplying them for individual connections.  Details about existing stacks at the time of writing are below. </del> <ins> Most major TLS implementations support external PSKs.  Stacks supporting external PSKs provide interfaces that applications may use when supplying them for individual connections.  Details about existing stacks at the time of writing are below. </ins> OpenSSL and BoringSSL: Applications specify support for external PSKs via distinct ciphersuites.  They also then configure callbacks that are invoked for PSK selection during the handshake. <del> These callbacks must provide a PSK identity (as a character string) and key (as a byte string).  (If no identity is provided, a default one is assumed.)  They are typically invoked with a PSK hint, i.e., the hint provided by the server as per RFC4279.  The PSK length is validated to be between [1, 256] bytes upon selection. </del> <ins> These callbacks must provide a PSK identity and key.  The exact format of the callback depends on the negotiated TLS protocol version with new callback functions added specifically to OpenSSL for TLS 1.3 RFC8446 PSK support.  The PSK length is validated to be between [1, 256] bytes.  The PSK identity may be up to 128 bytes long. </ins> mbedTLS: Client applications configure PSKs before creating a connection by providing the PSK identity and value inline. <del> Servers must implement callbacks similar to that of OpenSSL.  PSK lengths are validate to be between [1, 16] bytes. </del> <ins> Servers must implement callbacks similar to that of OpenSSL.  Both PSK identity and key lengths may be between [1, 16] bytes long. </ins> gnuTLS: Applications configure PSK values, either as raw byte <del> strings or hexadecimal strings.  The PSK size is not validated. </del> <ins> strings or hexadecimal strings.  The PSK identity and key size are not validated. </ins> wolfSSL: Applications configure PSKs with callbacks similar to OpenSSL.


Question:
FIxed up: some nits on recommendations. I think the wording was a bit off on low entropy PSKs, so I lifted from ekrs text from earlier in the draft. some of the stack interface stuff on hints is not valid for TLS1.3 (hints are TLS1.2 and earlier), so removed it. Some prelim text on collisions. For completeness, will take a look at gnutls and wolfssl order too. Note, even with the OpenSSL callback sequence, the application still does not know if there is a collision...
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Deployments should take care that the length of the PSK identity is sufficient to avoid obvious collisions. <del> [[OPEN ISSUE: discuss implication of collisions between external and resumption PSKs.]] </del> <ins> 6.1.2. It is possible, though unlikely, that an external PSK identity may clash with a resumption PSK identity.  The TLS stack implementation and sequencing of PSK callbacks influences the application's behaviour when identity collisions occur.  When a server receives a PSK identity in a TLS 1.3 ClientHello, some TLS stacks execute the application's registered callback function before checking the stack's internal session resumption cache.  This means that if a PSK identity collision occurs, the application will be given precedence over how to handle the PSK. </ins> 7.


Question: Ah, I see now. I think what would help is "in contrast to methods like RTX or flexfec (when retransmissions are used) [I-D.]"

indicated by congestion control and the receiver, this will lead to less bandwidth available for the primary encoding, even when the redundant data is not being used.  This is in contrast to methods <del> like RTX RFC4588 or flexfec I-D.ietf-payload-flexible-fec-scheme retransmissions, which only transmit redundant data when necessary, at the cost of an extra roundtrip. </del> <ins> like RTX RFC4588 or flexfec's retransmission mode ( I-D.ietf-payload- flexible-fec-scheme, Section 1.1.7), which only transmit redundant data when necessary, at the cost of an extra roundtrip. </ins> Given this, WebRTC implementations SHOULD consider using RTX or flexfec retransmissions instead of FEC when RTT is low, and SHOULD


Question: It's similar to the redundant encoding, but done within the Opus bitstream, rather than at the RTP level.

This approach, as described in RFC2198, allows for redundant data to be piggybacked on an existing primary encoding, all in a single packet.  This redundant data may be an exact copy of a previous <del> packet, or for codecs that support variable-bitrate encodings, </del> <ins> payload, or for codecs that support variable-bitrate encodings, </ins> possibly a smaller, lower-quality representation.  In certain cases, <del> the redundant data could include multiple prior packets. </del> <ins> the redundant data could include encodings of multiple prior audio frames. </ins> Since there is only a single set of packet headers, this approach allows for a very efficient representation of primary + redundant


Question: It's similar to the redundant encoding, but done within the Opus bitstream, rather than at the RTP level.

Some audio codecs, notably Opus RFC6716 and AMR RFC4867, support their own in-band FEC mechanism, where redundant data is included in <del> the codec payload. </del> <ins> the codec payload.  This is similar to the redundant encoding mechanism described above, but as it adds no additional framing, it can be slightly more efficient. </ins> <del> For Opus, packets deemed as important are re-encoded at a lower bitrate and added to the subsequent packet, allowing partial recovery </del> <ins> For Opus, audio frames deemed important are re-encoded at a lower bitrate and appended to the next payload, allowing partial recovery </ins> of a lost packet.  This scheme is fairly efficient; experiments performed indicate that when Opus FEC is used, the overhead imposed <del> is about 20-30%, depending on the amount of protection needed.  Note that this mechanism can only carry redundancy information for the immediately preceding packet; as such the decoder cannot fully recover multiple consecutive lost packets, which can be a problem on wireless networks.  See RFC6716, Section 2.1.7 for complete details. </del> <ins> is only about 20-30%, depending on the amount of protection needed. Note that this mechanism can only carry redundancy information for the immediately preceding audio frame; as such the decoder cannot fully recover multiple consecutive lost packets, which can be a problem on wireless networks.  See RFC6716, Section 2.1.7 for complete details. </ins> For AMR/AMR-WB, packets can contain copies or lower-quality encodings <del> of multiple prior audio frames.  This mechanism is similar to the redundant encoding mechanism described above, but as it adds no additional framing, it can be slightly more efficient.  See RFC4867, Section 3.7.1 for details on this mechanism. </del> <ins> of multiple prior audio frames.  See RFC4867, Section 3.7.1 for details on this mechanism. </ins> In-band FEC mechanisms cannot recover any of the RTP header.


Question: It's similar to the redundant encoding, but done within the Opus bitstream, rather than at the RTP level.

Support for a SSRC-multiplexed flexfec stream to protect a given RTP stream SHOULD be indicated by including one of the formats described <del> in I-D.ietf-payload-flexible-fec-scheme, Section 5.1, as an </del> <ins> in I-D.ietf-payload-flexible-fec-scheme, Section 5.1.2, as an </ins> additional supported media type for the associated m= section in the SDP offer RFC3264.  As mentioned above, when BUNDLE is used, only a single flexfec repair stream will be created for each BUNDLE group,


Question:
The discovery fields for the interaction methods were still in a single list, even though those have now been split into start and finish sections.
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Yes, makes sense

result MAY be used by the client instance in the request- capabilities of the request. <del> OPTIONAL.  A list of the AS's interaction methods.  The values of this list correspond to the possible fields in the request- interact of the request. </del> <ins> OPTIONAL.  A list of the AS's interaction start methods.  The values of this list correspond to the possible values for the request-interact-start of the request. OPTIONAL.  A list of the AS's interaction finish methods.  The values of this list correspond to the possible values for the method element of the request-interact-finish of the request. </ins> OPTIONAL.  A list of the AS's supported key proofing mechanisms. The values of this list correspond to possible values of the


Question:
remove OAuth DPoP binding. Described why on IETF mailing list: only works for asymmetric keys, requires key be presented in the header (duplicating information from GNAP messages). It was never meant to be a general purpose signing mechanism, though the FAPI group in OIDF is considering it as an option in current proposed work.
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Ok that's weird (just removed some lines...), will have a look
Ok that was due to my rust analyser in vscode, fixed it now

Mutual TLS certificate verification <del> OAuth Demonstration of Proof-of-Possession key proof header </del> HTTP Signing signature header OAuth PoP key proof authentication header


Question:
remove OAuth DPoP binding. Described why on IETF mailing list: only works for asymmetric keys, requires key be presented in the header (duplicating information from GNAP messages). It was never meant to be a general purpose signing mechanism, though the FAPI group in OIDF is considering it as an option in current proposed work.
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Ok that's weird (just removed some lines...), will have a look
Ok that was due to my rust analyser in vscode, fixed it now

7.3.4. <del> This method is indicated by "dpop" in the "proof" field.  The signer creates a Demonstration of Proof-of-Possession signature header as described in I-D.ietf-oauth-dpop section 2.  In addition, this specification defines the following fields to be added to the DPoP payload: Digest of the request body as the value of the Digest header defined in RFC3230.  When a request contains a message body, such as a POST or PUT request, this field is REQUIRED. In this example, the request body is the following JSON object: ~~~ { "access_token": { "access": [ "dolphin-metadata" ] }, "interact": { "start": ["redirect"], "finish": { "method": "redirect", "uri": "https://client.foo/callback", "nonce": "VJLO6A4CAYLBXHTR0KRO" } }, "client": { "proof": "dpop", "key": { "jwk": { "kid": "gnap-rsa", "kty": "RSA", "e": "AQAB", "alg": "RS256", "n": "hYOJ- XOKISdMMShn_G4W9m20mT0VWtQBsmBBkI2cmRt4Ai8Bf YdHsFzAtYKOjpBR1RpKpJmVKxIGNy0g6Z3ad2XYsh8KowlyVy8IkZ8NMwSrcUIBZG YXjHpwjzvfGvXH_5KJlnR3_uRUp4Z4Ujk2bCaKegDn11V2vxE41hqaPUnhRZxe0jR ETddzsE3mu1SK8dTCROjwUl14mUNo8iTrTm4n0qDadz8BkPo-uv4BC0bunS0K3bA_ 3UgVp7zBlQFoFnLTO2uWp_muLEWGl67gBq9MO3brKXfGhi3kOzywzwPTuq-cVQDyE N7aL0SxCb3Hc4IdqDaMg8qHUyObpPitDQ" } } "display": { "name": "My Client Display Name", "uri": "https://client.foo/" }, } } ~~~ The JOSE header contains the following parameters, including the public key: The JWS Payload contains the following JWT claims, including a hash of the body: This results in the following full HTTP message request: The verifier MUST parse and validate the DPoP proof header as defined in I-D.ietf-oauth-dpop.  If the HTTP message request includes a message body, the verifier MUST calculate the digest of the body and compare it to the "htd" value.  The verifier MUST ensure the key presented in the DPoP proof header is the same as the expected key of the signer. 7.3.5. </del> This method is indicated by "httpsig" in the "proof" field.  The sender creates an HTTP Message Signature as described in I-D.ietf- httpbis-message-signatures.


Question:
remove OAuth DPoP binding. Described why on IETF mailing list: only works for asymmetric keys, requires key be presented in the header (duplicating information from GNAP messages). It was never meant to be a general purpose signing mechanism, though the FAPI group in OIDF is considering it as an option in current proposed work.
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Ok that's weird (just removed some lines...), will have a look
Ok that was due to my rust analyser in vscode, fixed it now

The verifier MUST validate the signature against the expected key of the signer. <del> 7.3.6. </del> <ins> 7.3.5. </ins> This method is indicated by "oauthpop" in the "proof" field.  The signer creates an HTTP Authorization PoP header as described in I-


Question:
The boolean value "true" is no longer used to specify supported interaction start modes.
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If the client instance is capable of directing the end-user to a URL defined by the AS at runtime, the client instance indicates this by <del> sending the "redirect" field with the boolean value "true".  The means by which the client instance will activate this URL is out of scope of this specification, but common methods include an HTTP redirect, launching a browser on the end-user's device, providing a scannable image encoding, and printing out a URL to an interactive console.  While this URL is generally hosted at the AS, the client instance can make no assumptions about its contents, composition, or relationship to the AS grant URL. </del> <ins> including "redirect" in the array under the "start" key.  The means by which the client instance will activate this URL is out of scope of this specification, but common methods include an HTTP redirect, launching a browser on the end-user's device, providing a scannable image encoding, and printing out a URL to an interactive console. While this URL is generally hosted at the AS, the client instance can make no assumptions about its contents, composition, or relationship to the AS grant URL. </ins> If this interaction mode is supported for this client instance and request, the AS returns a redirect interaction response response-


Question:
The boolean value "true" is no longer used to specify supported interaction start modes.
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If the client instance can open a URL associated with an application on the end-user's device, the client instance indicates this by <del> sending the "app" field with boolean value "true".  The means by </del> <ins> including "app" in the array under the "start" key.  The means by </ins> which the client instance determines the application to open with this URL are out of scope of this specification.


Question:
The boolean value "true" is no longer used to specify supported interaction start modes.
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If the client instance is capable of displaying or otherwise communicating a short, human-entered code to the RO, the client <del> instance indicates this by sending the "user_code" field with the boolean value "true".  This code is to be entered at a static URL that does not change at runtime.  While this URL is generally hosted at the AS, the client instance can make no assumptions about its </del> <ins> instance indicates this by including "user_code" in the array under the "start" key.  This code is to be entered at a static URL that does not change at runtime.  While this URL is generally hosted at the AS, the client instance can make no assumptions about its </ins> contents, composition, or relationship to the AS grant URL. If this interaction mode is supported for this client instance and