instruction stringlengths 32 27.2k |
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If I have a long randomly generated key (k), XORed with a message (m), but since the message is longer than the key, there is a chance of reusing the keystream with the same message, but the key is used only onetime for every encryption process. In other words, every time I have to encrypt a message, I randomly generat... |
The definition of Public Key Encryption(PKE) say that:
A PKE scheme is a triple of probabilistic polynomial time algorithm (PPT) (Gen,Enc,Dec).
The definition of PPT say:
In complexity theory, PP is the class of decision problems solvable by a probabilistic Turing machine in polynomial time, with an error probabilit... |
For RSA cryptography, we know that the modulo $n$ is a product of two big prime numbers(say $p$ and $q$). However, in some documents I see an extension of $p=2p'+1$ and $q=2q'+1$ with $q'$ and $p'$ being huge prime numbers.
Why is it necessary to have $n=pq$ with $p=2p'+1$ and $q=2q'+1$ instead of just $n=p'q'$ when we... |
I'm reading a Definition of Public Key Encryption and here say:
...
Enc is a (possibly) probabilistic polynomial time encryption algorithm which takes as input a public key $pk$, a $m\in M$ and random coins $r$, and outputs a ciphertext $c\in C$.
But in other papers, there is no mention of coins $r$.
Can you give ... |
Given is a square matrix $M$ over a field $F$, we have a key exchange with the following conditions:
Person $X$ sends a message to Person $Y$: $C_{1}=AM$, where $A$ is a randomly chosen square matrix.
Person $Y$ sends a message to Person $X$: $C_{2}=MB$, where $B$ is a randomly chosen square matrix.
Both can compute t... |
This cipher shifts the letter that it will shift to, after each shift...
I used to play with this when I was a kid. I was thinking about it recently and realized that it wasn't as simple as I thought. Here's the description:
The second number makes the code much harder to break. It changes the number of letters above ... |
I want to design a secure data container that can be used to transfer encrypted data over a public network that can defeat common attacks. Data is already encrypted before entering this container so that is out of scope. The container need to store some detail about the cipher used so that it can be properly decrypted ... |
In studying modern (and classical) cryptography, many notions from information theory crop up. Unicity distance, min-entropy, compression, encoding, etc. What parts of information theory should be part of the knowledge corpus of a working cryptographer?
|
Currently I'm working on a presentation of a paper that talks about the factorization of large numbers. In the paper elliptic curves are presented as a way to factorize large numbers. After hearing a lot about elliptic curves it's the first time that I delve into the details of elliptic curves and I'm a bit bit baffled... |
Currently I'm doing some initial research for a fully connected distributed network communication model. The context here is a peer-to-peer multiplayer protocol, using a majority-voting system. More specifically, it's distributed lockstep used in most (all?) RTS games; somewhat similar to: Age of Empires.
Given the na... |
Some time ago I was working in a pet project for a type of database engine. And I thought about securing the data in disk with encryption.. and since the main code was already developed.. I had a few requirements..
a simple stream class that I could hook instead of my file stream had
to support random access (both rea... |
I'm not sure why in the Goldwasser-Micali encryption scheme with a Blum integer $N$, the message $-1$ is always a illegal message.
Can you give me some direction for starting?
What is illegal message's meaning?
|
We are given n (public modulus) where n=pq and e (encryption exponent). Then I was able to crack the private key d, using Wieners attack. So now, I have (n,e,d). My question is, is there a way to calculate p and q from this information? If so, any links and explanation would be much appreciated!
|
For a hash function, what's the difference between Collision Resistance and Target Collision Resistance?.
I understand the definition of hash function collision resistance, but I don't know about Target Collision Resistance.
|
I have an unsubscribe link, which needs to be passed a customer id, and a product id, producing a query string something like:
?cid=100&pid=2
I would like to ensure the customer is the one doing the unsubscribing, and that they are unsubscribing from the exact product. HMAC seems like a logical choice:
?cid=100&pid=2... |
I found this question from a textbook but I don't really understand what it is asking:
Suppose $c$ is $1$ block long, $a$ and $b$ are strings that are a multiple of the block length, and $\text{CBC-MAC}(a||c) = \text{CBC-MAC}(b||c)$. An ideal block cipher is used in $\text{CBC-MAC}$.
Explain for which most general clas... |
There seems to be sources like this, this also, and some introductions that discuss elliptic curves in general and how they're used. But what I'd like to know is why these particular curves are so important in cryptography as opposed to, let's say, any other polynomial degree $\gt$ 2 which you can then mod over some g... |
Let $N=PQ$, where $P=2p+1$ and $Q=2q+1$. $P,Q,p,q$ are prime numbers. $QR_{N}$ is the set of quadratic residues modulo $N$.
Please help me to prove $QR_{N}$ is a cyclic group. Note: $QR_{P}$ and $QR_{Q}$ are cyclic groups.
How to find/determine generator for $QR_{N}$?
|
I am trying to find an implementation or variant of a (k, n) threshold cryptosystem (as described here Shamir's Secret Sharing) where we can fix at least one of the k key parts, i.e., instead of ANY k key parts able to decrypt the ciphertext I want at least one of the k key parts to be a certain/fixed key part. So sort... |
I have a question regarding the paper "Fully Homomorphic Encryption over the Integers"
(http://eprint.iacr.org/2009/616.pdf): On page 6 after they set their parameters, it says
"This setting results in a scheme with complexity $\overset{\sim}{\mathcal{O}}(λ^{10}).$"
What exactly do they mean by this? That the runtime... |
I'm not talking about scytale, but encryption like RSA, DES, etc.
How exactly did civil cryptography evolve after World War II?
|
I suggested mulitiplicative secret sharing in an answer to another question, but noted that I wasn't sure if it was even secure and was hoping someone would comment on the security. Since no one did, I thought I'd ask it as a separate question.
Fix a multiplicative group, say $\mathbb{Z}_p^*$.
To share $s$ with $k$ par... |
I found this question about CBC-MAC forging and want to make sure I understand it:
Let a and be be two strings of block length one. Suppose the sender sends $(a, \text{CBC-MAC}(a)), (b, \text{CBC-MAC}(b)), (a||b, \text{CBC-MAC}(a||b))$. Find new messages / MAC pair which the attack can now forge from the messages / MA... |
I would like to prompt users for a single passphrase to establish trust with separate, normally (but not always) complementary systems from one password input.
I'm essentially looking for a box where one password enters and two leave, where maximum of entropy is maintained and the ability of an attacker using either ou... |
Let $ PRG: \{ 0, 1\}^n \rightarrow \{ 0, 1\}^{n+s}$ be a pseudo random generator and let $A$ be an inverter that runs in polynomial time, specifically:
$\large \mathbb P_{d \leftarrow PRG(U_n)}[ A(d) = v, PRG(v) = d] \ \ge \ \delta$
Show how to construct a polynomial distinguisher $B$ that uses $A$ to distinguish $PRG(... |
The biclique attacks that break AES (Biclique Cryptanalysis of the full AES) appear to require decryption oracles to work, presumably because the key schedule of AES is weaker in the decryption direction, enabling better bicliques to be constructed starting from the ciphertext end. Which is to say, these attacks show ... |
Can someone please explain what key sizes are required for the ECDSA algorithm?
I tried a 128 bit EC Key for SHA1withECDSA and it throws an error. However with 256 bit key I could run the algorithm. Therefore want to know what key sizes are required for the different ECDSA algorithm with SHA1 and SHA2.
Also, how does ... |
I know nothing of encrypting. I'm not even sure how to tag this.
I wrote a program that can calculate this pretty quickly on my macbook pro 2.3GHz IntelCore i7. The two exponents are Mersenne primes, and no I did not use floats.
It calculated ((2^756839)-1) * ((2^1257787)-1) = a number 606,463 digits long. The exponent... |
I'm looking for different approaches to proofs for the security of CBC mode encryption. What are the best sources of information about this subject?
|
I'm trying to find a bijective function $y=F(x)$ which should be easy to compute in one direction but hard to compute in the other, where the one-way property is not based on a number theoretic assumption.
The hard direction should be preferably as hard as computing hash preimages, but it could also be that there is on... |
I have question about how a user's identity is verified by a Certification Authority.
As I understand it, the process works as follows:
User generates his private key and (with the help of private key) generates his public key.
Now user want to register his public key. For this, he has to send the public key to CA.
Us... |
I'd like to use OpenPGP authentication over TLS, but lack of implementations made me use a temporary solution: an OpenPGP/X.509 bridge certificate.
The approach is very similar to the approach used in Foaf:
https://svn.java.net/svn/sommer~svn/trunk/misc/FoafServer/pgpx509/src/net/java/dev/sommer/foafserver/utils/PgpX50... |
While reading "Certificateless Public Key Cryptography" by Author Sattam S. Al-Riyami and Kenneth G. Paterson, they have considered generation of private keys by a Key Generation Center (KGC). If the KGC gets compromised it will break security, so why should a KGC generate private keys.
Will it be possible that user wi... |
I wish to encrypt credit card numbers one by one using asymmetric encryption on the command line. My current approach is this…
Encrypt:
/usr/bin/openssl rsautl -encrypt -inkey 'myKey.pub' -pubin | /usr/bin/openssl enc -base64
Decrypt:
openssl enc -base64 -d | openssl rsautl -decrypt -inkey myKey.pem
It is my understa... |
Most of the papers on block cipher constructions, especially the ones which discuss constructing block ciphers of arbitrary lengths or small domains, the techniques are designed based on building a PRP from a PRF. The ones that are based on Luby-Rackoff etc.
Why is it that the input message first to be processed by a p... |
Are there are any cryptographic protocols or algorithms that can prevent active MITM attacks or interference when initiating a new connection to a server or someone you have not exchange keys with before?
For example:
Alice's computer ➜ ISP ➜ Internet ➜ ISP ➜ Bob's server
It is known that ISPs are compromised with sec... |
I am trying to sign certificate (X509) using secret sharing. That is shareholders combine their signatures to produce the final signature which will be in this case the signed certificate. However practically from my understanding only one entity can sign a certificate. Therefore I want to know:
which entities or data... |
I've received a public key to encrypt my data for the other end to decrypt using their private key. Now, they want us to sign the data as well to ensure non-repudiation.
I thought that I should only sign using a private key (which isn't in my possession). How do I sign my encrypted data?
|
Format preserving encryption has three modes FE1( FFX) , FE2(VAES) , FE3(BPS) . All of them are based on Feistel Networks .Can somebody explain how they differ from each other ?
|
I'm having trouble with the following question from my class:
"What is the purpose of the protocol, and how does it achieve this purpose and what shared information does A and B end up after running an instance of this protocol?
$\sf A \to B: \quad A, N_A$
$\sf B \to S: \quad B, \{A, N_A, T_B\} K_{BS}, N_B$
$\sf S \t... |
I was just reading Ars Technica's primer on ECC. Somewhere near the middle of the second page, the author introduces the "dot" operation that takes an elliptic curve and two other known points, giving a third unique point.
However, the author then claims that A dot A equals B. That is, if the two first points are the s... |
In order to be indistinguishable with respect to multiple messages, wouldn't the scheme need to be nondeterministic? How would this then possibly be vulnerable to an adaptive CPA?
|
I am a hobby programmer with a background in biology and have developed an encryption program based on DNA. I tried to make it hard to crack, but it's essentially a substitution cipher and uses the default Java random number generator so my guess it could be cracked relatively easily. But how do I find out how good my ... |
In Merkle–Damgård transform, a fixed vector IV is chosen at the beginning, and it is hashed together with the first block x1. I wonder why we don't use x1 straightforward, i.e. hash x1 and the next block x2 at the very beginning.
|
DES uses 16 rounds of feistel networks but not considered secure . Where Luby Rackoff constructions which are inspired by DES its proven by Patarin that 7 rounds is secure .
Is there a relation between number of rounds in DES and patarin's results ?
|
I've seen that there is several kinds of PRF, and sometimes people speak about strong PRFs.
When proofs of a protocol or algorithm are given based on the assumption of the use of a PRF, are they speak implicitly about strong PRFs?
|
I've read the following two questions and their answers:
Messages of different lengths and one-time computationally-secret
Why is a non fixed-length encryption scheme worse than a fixed-length one?
I am still not convinced of what is the actual strategy of the adversary $A$. I understand that in case that the encrypt... |
Would the property of perfect forward secrecy still be achieved in MTI/A0 for a session key that was established between C and D when one LL-key aD is revealed so that both LL-keys aC and aD are revealed?
|
Is there any way to generate values only between $0$ and $255$ with the Diffie-Hellman method? I need to create keys for communication algorithms with $32$ and $16$ numbers between that range.
The idea is to exchange the keys between the participants using the results of the Diffie-Hellman key agreement algorithm. Then... |
I have a file that has been encrypted using DES and am looking to decrypt and find a secret message encoded. All I have is the file which is full of binary data. There is no key or anything else which makes me wonder how can I be able to do it by Brute Force.
I spent some time reading and understanding DES and I know ... |
I'm not completely clueless as to what it means, but I'd like to understand it at a higher level.
The highest encryption type used by Active Directory domain controllers for Kerberos authentication traffic is AES256-CTS-HMAC-SHA1-96.
The first part: AES256-CTS. That's AES with a 256-bit symmetric key operating in Ciphe... |
It's well-known that Shor's algorithm can solve integer factorization, discrete logarithm and discrete log over elliptic curves in cubic time. This implies that cryptosystems like RSA, ElGamal, and Elliptic Curve Diffie-Hellman (ECDH) are vulnerable to quantum computers.
Are there any existing public-key cryptosystem ... |
I'm reading the paper “Collision-Resistant Hashing? Towards Making UOWHFs Practical” which states:
With an ACR hash function $F$ the key $K$ is announced and the adversary wins if she manages to any collision $M,M'$ for $f = F_K$. The points $M$ and $M'$ may depend arbitrarily on $K$.
Could you give me an example of ... |
I'm reading the paper “Collision-Resistant Hashing? Towards Making UOWHFs Practical” which states:
While it might be easy to find a collision $M,M'$ in $F_K$ by making both
$M,M'$ depend on $K$ (Any Collision Resistance), the adversary may be unable to find collisions if she
is forced to commit to one point of the... |
I'm reading the paper “Collision-Resistant Hashing? Towards Making UOWHFs Practical” , which compared TCR (Target Collision Resistant) and ACR (Any collision Resistant). It says
we wish to stress one important practical advantage of TCR over ACR: because $x$ must be specified before $K$ is known, birthday attacks to f... |
Consider GregS's comment to this question (more specific to bouncycastle's provider implementation):
https://stackoverflow.com/questions/11717646/bouncycastle-rsa-key-size-and-padding
The mode, ECB in this case, is ignored for RSA.Use PKCSPadding. The
max amount of data you can encrypt is the size of the modulus in ... |
These days, the best practice for storing passwords is to use a scheme like scrypt or bcrypt. The goal of these schemes is to make dictionary attack inefficient for an attacker but it also slows down legitimate use of the function.
If you're doing thousands of password checks per second, there is a real world cost of ... |
I really don't know how to call this simple problem: Two (or more) parties need to establish a common (non-secret) value to be used as a seed for a deterministic RNG. The only requirement is that each party can be sure that the seed is really random.
My idea is as follows:
Each party generates a random value $x_i$,
se... |
Alice has a message, generates a one time pad, encrypts her message and sends it to Bob. Bob generates his own one time pad, encrypts the message again, and sends it back to Alice. Alice then decrypts this message using her one time pad, sends it back to Bob who then decrypts it the last time using his one time pad.
Th... |
I'm developing my own protocol and I'll use Diffie-Hellman to achieve PFS. It will work in this way:
The symmetric encryption algorithm will be AES_256_CBC.
The DH parameters will be:
P: a 2048-bit safe prime as defined in RFC 3526.
Generator: 2 (also defined in RFC 3526).
Secret Exponent: a 512-bit ephemeral random nu... |
In a PostgreSQL database, I can see the following fields in a table (for a specific record):
User = administrator
Password = "ceMv9Me6go"
Now the following are true:
The password length is not fixed, thus I'm leaning towards it being an
encryption rather than a hash.
The actual password is "password"
Salt is unknown ... |
There are many RFC documents giving large primes to use in Diffie-Hellman. However, I couldn't find standards on the $p$ and $q$ large primes used in the DSA signature scheme. This is proving to be a major obstacle in my own toy implementation of DSA, as generating these primes uses much messier math and code than the ... |
Basically the title says it all. It would be great if someone could tell give an example using provable security. More information about groups can be found at:
https://en.wikipedia.org/wiki/Group_(mathematics)
https://en.wikipedia.org/wiki/Group-based_cryptography
|
Related to the algorithms of certificate-less Signature approach of Al-Riyami and Paterson…
Why is there a need for a "partial private key extract algorithm"?
Why should it be needed when calculating "user's private keys by user"?
Is "partial private key extract algorithm" further used in other algorithms?
|
Suppose I have H(M|K) and that H is not weakly collision resistant. If I have a message mac pair (M,MAC), how is it possible to find another message mac pair (M2,MAC2)? My thinking for this problem is that if the hash isn't weakly collision resistant, then I can find another message M2 such that H(M|K)=H(M2|K) and thus... |
I'm reading “Collision-Resistant Hashing? Towards Making UOWHFs Practical” and in the Section 2 it says:
Hash functions like MD5 or SHA-1 have no explicit key. But no notion
of collision-freeness has been offered for such a keyless setting. To
get a sense why this is so, suppose $f$ is a function $f:\sum^*\righta... |
I have been trying to understand how secret sharing methods like Shamir's secret sharing solve the problem of a share revealing information about the secret. I guess there are some random numbers involved, but how is it done mathematically?
|
What is the best way to implement a cascade encryption?
I'm trying to figure out how to cipher a string (or message) using Serpent-Twofish-AES and then store the keys.
I'll provide an explanation, then maybe someone is going to be able to explain how to resolve the issue I'm facing. I've read the TrueCrypt documentatio... |
I know that SHA-1 is an unkeyed cryptographic hash function when used in practice. But, in the theory, all hash function are defined with keys. My question is:
How I will be able to formalize the SHA-1 hash function using keys?
In security proof, which approach could be used - theoretical or practical?
|
Ok, so this is a very possible stupid question, but one of those things that has sat at the back of my mind for a while.
We all know that MD5 has issues, and these have been known for about a decade. So this is theoretical. I'm not considering using it for anything.
Question is this. If MD5 generates a 32 digit numb... |
Imagine I'm signing up for the 99th new web site this month.
I somehow take my secret key (which I have written down on a card in my wallet) and the domain name of the site and feed them both into some algorithm (perhaps a HMAC?),
and type the resulting hash into the "password" field of the registration form.
Later, I'... |
Given two sets of plaintexts and their corresponding ciphertexts, how does one determine the key $K$?
The ciphertexts are:
$$C_1= (P_1 \oplus K_0) + K_1$$
and
$$C_2= (P_2 \oplus K_0) + K_1$$
$K = K_0 || K_1$ (string of bits).
where $+$ means addition mod $2^n$.
How do we find the unknowns (eg, $K_1$)?
|
I have been given a problem in preparation for my cryptography final that I'm not sure how to solve. It asks me to suppose a scenario where instead of where an attacker would intercept some message from Alice ($g^a$) mod p and ($g^b$) mod p from bob, and then replacing each of these with $g^e$, the attacker would repla... |
I commonly hear statements along the lines of "all cryptograms are crackable - it's only a matter of time".
Is there a proof to show that any cryptogram is "crackable"? The proof may be of a more philosophical form rather than relying on mathematical proofs. I really don't know what to expect, but would be fascinated b... |
The NSA recently released SIMON and SPECK light weight block ciphers. Although initial spec release did not have much of cryptanalysis details, two works later appeared providing the cryptanalysis for the same SIMON and SPECK.
But how should we interpret those results? Are they considered good or bad?
For example:
At... |
When working with an additive homomorphic encryption scheme (say Pallier's), is there an efficient way to get the encrypted value of a comparison test to an integer value (I realise that an unencrypted comparison test would make the encryption scheme worthless)?
I know there are (rather costly in number of rounds and ... |
To get a public key of some organization or someone we want to send an encrypted message to, we need to make a request to CA asking that organization's public key. CA then returns X509 certificate. It contains CA's signature. To decrypt it we need to have a CA's public key. How can we securely obtain CA's public key?
R... |
How does certificate revocation list (CRL) work? How can I send a request to the CA to add my current private key to the CRL, so no one except me can add my certificate to the CRL?
Related:
- How can we get CA's public key?
- I've got my private key compromised. How does CRL work?
- What happens when a root CA has its ... |
What happens when a root CA has its private key compromised? Then all children in the tree are compromised too? And then all certificates are compromised? What needs to happen then?
Related:
- How can we get CA's public key?
- I've got my private key compromised. How does CRL work?
- What happens when a root CA has its... |
Routers could just use Diffie-Hellman protocol with any computer who tries to connect to that router. Then it would be impossible to eavesdrop for anyone. Only router and computer would know the secret key for that session. No?
Or someone could act as a router and send his own public key and get the traffic through his... |
Why have 4th and 5th steps in Needham-Schroeder Protocol? It is said "These steps assure B that the original message it received (step 3) was not a
replay.". But what is a replay here? And I don't actually get what those 4th and 5th steps do. Send some nonce?
Here is the protocol outline I am looking at (source)
$$
\b... |
Reading Schneier's "The Doghouse: Crypteto" dated September 30, 2009, I noticed Bruce Schneier stating:
Threefish, the block cipher inside Skein, encrypts data at 7.6 clock cycles/byte with a 256-bit key, 6.1 clock cycles/byte with a 512-bit key, and 6.5 clock cycles/byte with a 1024-bit key.
and
I'm not claiming t... |
In this paper at the bottom of pg. 1235 and beginning of pg. 1236 it says:
An MPC protocol is said to be secure, if for every real world leakage
adversary A there exists an ideal world simulator S, such that the
output of all the parties (including the adversary) in the real world,
is computationally indistingu... |
I understand that if you have a message $m$, you can blind it by selecting a random $r$ and then multiplying $r^e\times m \pmod{n}$ Someone else then signs it with $d$, raising to the power of $d$: $(r^{ed}\times m^d) \bmod n = r \times m^d$. Finally to unblind: $r^{-1}\times r \times m^d = m^d$ and $\left(m^d\right)... |
I'm reading a proof of the proposition of CollisionResistant Hashing Towards Making UOWHFs Practical
Suppose there exists a compression function $F: \Sigma^k\times\Sigma^{c+m'} \rightarrow \Sigma^c$ with $m'>k$ such that $F$ is $(t',\epsilon')$-resistant to target collisions. Then there exists a compression function ... |
In the elliptic curve: $y^2 = x^3 + 20x + 13 \bmod{2111}$.
Using the point $P=(3, 10)$
I am wondering how to multiply this point by the scalar $57$?
I realize I can write $57*P$ as $2^5*P + 2^4*P + 2^3*P + P = 2(2(2(2(2P)))) + 2(2(2(2P))) +2(2(2P)) + P$.
My question is what is the best way to calculate these doubles a... |
During my master thesis I came across RSA-PSS-R which is in my opinion a quite elegant way of saving bandwidth and space using digital signature.
But I didn't find any information about any real world implementation out there. I have the feeling that it's exactly like the Schnorr Signature scheme. Everybody says that i... |
Consider protocol like QUIC or MinimaLT which are essentially layer4 replacement for TCP/UDP (riding on top of UDP currently because of fear of random firewalls dropping new L4 protocol).
From crypto point of view they are mostly the same designs (using same EC stuff djb has done). IP addresses are not relevant for ide... |
We have a game $G0$ for which an adversary $A$ has access to a certain amount of ressources. Let us suppose that the maximum advantage for the adversary to win this game is $Adv_{G0}$.
If we modify slightly the game $G0$ into the game $G1$ in such way that we give an additional information (useful or not) to this adver... |
I'd like to know how much bigger is the ciphertext when encrypting a message using ECC encrytpion? ECIES (or ElGamal)
|
We have a business requirement to keep credit card data. What is today's (Nov 2013) state of the art algorithm to encrypt credit card data that will be saved on disk? Additionally, I'd appreciate pointers to Java libraries that implement these algorithms
Note that we are PCI compliant and we already store credit card d... |
Disclaimer: This is exercise 2.1 in Katz-Lindell book.
Given a (symmetric) encryption scheme $\Pi=(Gen,Enc,Dec)$ where $Gen$ takes the security parameter $1^n$ as input and generates a key $k$ of length $n$.
Usually we simply assume that $Gen$ chooses key uniformly from $\{0,1\}^n$ but this is not always the case.
Give... |
Can you explain the actual attack?
Why does the attacker need to firstly send some arbitrary UDP packet?
How can the attacker break the privacy between A and B?
Link: The article of Bellovin
I'm attaching the slide for a reminder:
|
In this paper on pg. 1236, under the section "Security Against Continual Leakage", the authors say:
"We further remark that the weaker security notion previously
achieved cannot be extended meaningfully to continual leakage in the
MPC setting. That is, it cannot address the setting where the $n$ users
do not ju... |
I see in some “Authentication schemes with biometric” papers that those authors wrote a phase as password and biometric update phase.
My question is that why we may needs biometric update phase?
Is not biometric (say finger print or iris or face and …) permanent properties?
|
I want to implement a basic version of Diffie-Hellman key agreement for groups.
So, my key is $K=g^{abc} \mod p$. Following this, the parameters I would need to transfer would be $K_a = g^{bc}$ etc. The group may become large (up to 100 member), so I don't want to calculate every parameter anew and reuse $K$. Is there ... |
Most of the encryption modes of Feistel Networks especially the ones used to build fixed length block ciphers just provide confidentiality .
Can we build authenticated encryption using Feistel Networks ?
|
http://en.wikipedia.org/wiki/One-time_password#How_OTPs_are_generated_and_distributed
Why have so many methods to generate OTPs, why not just use just random strings?
|
I have been reading about the Challenge-Handshake authentication Protocol (aka CHAP).
Why send a challenge to the user and ask them to hash that challenge with the symmetric key and send that hash back to the server? Why not just ask for a hash value of a symmetric key? And what is the point of this protocol at all whe... |
I want a key stretching system that's as strong as the stronger of scrypt and PBKDF2. The consensus now is that scrypt is by far the better system, but that might change if in the future, a weakness is found in Salsa20. Here is a proposed system that I dreamed up, does it seem like a good idea?
First run scrypt and pr... |
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