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I have a long list of items with non-random id numbers. I then compute the hashes of the ids (using SHA256 or something similar).
If I now pick all ids where, say, the last digit of the hash is a 3, is that equivalent to a random sample? I know that looking at the hash I can't infer if the id number was odd or even. Do... |
I refer to Should we MAC-then-encrypt or encrypt-then-MAC?.
There are 15 answers (today) with many words. It is difficult to tell which is the correct(?) answer. Also, the question excludes the concept of informationally secure universal hashing, or the effects of the application of a one time pad to the (H)MAC.
The or... |
I am considering the following problem related to Learning with Errors. Recall that the LWE assumption is that no adversary can distinguish $(A,As+e)$ from $(A,u)$ with non-negligible advantage, where $A\in\mathbb Z_q^{m\times n}$ and $u\in\mathbb Z_q^m$ are random and $e\in\mathbb Z_q^m$ is a random vector each elemen... |
I want to read this kind of diagram, but I haven't found the name of this, or somewhere I can find a legend of symbols used, or a tutorial to learn reading this...
I've googled this for over an hour, with similar images. Nothing :/
|
Suppose I want to send a message, but not privately; I want everybody to see it, even an attacker in the middle. I would do this by appending a public key to the start of the data, which could be used to decrypt an HMAC attachment, and verify that I sent it.
Is this feasible? Would this still ensure the integrity of th... |
Is there an encryption algorithm or MAC algorithm for which NO zero-knowledge-proof exists, provably? I want people who want to prove that a ciphertext decrypts into some plaintext to have to spoil the key for decryption, or if they want to prove that message's MAC is some given MAC then they have to spoil the key for ... |
I'm trying to perform a hash update with updated parameters using argon2. According to Argon spec v3 (2.2.3 Client-indepentend Update, p. 9) the client independent update is executed as follows:
$$
Tag_{new} = \Pi(Tag_{old},S,m_{new},R_{new},\tau_{new})
$$
I'm assuming $\Pi$ to be our hash fn Argon2i/Argon2d (as used i... |
I want to use DCR-based functional encryption for encryption and decryption purpose. However, I'm unsure whether DCR-based functional encryption can support negative integers.
Is there any implementation or construction of functional encryption where negative integers are encrypted/decrypted?
|
What the benefit of the shared key that generated from ECDH key exchange protocol?
Can I use it to encrypt the message or encrypt the public key of asymmetric encryption?
|
In the practical application of secure multi-party computation, the operation of division is inevitable. But I don't know how to construct a division?
In order to make the problem more accurate and easy to understand and answer, the following three mainstream paths are used to directly benchmark specific algorithms to ... |
Given the following curve:
$$ y^3 = x^2 - 7x $$
over the finite field $GF(271)$.
We have $P = (201, 247)$ belongs to the curve:
$$ 247^2 \equiv 201^3 - 7 \cdot 201 \equiv 34 \mod 271 $$
We also have $Q = (201, 24)$ belongs to the curve:
$$ 24^2 \equiv 201^3 - 7 \cdot 201 \equiv 34 \mod 271 $$
So, how to add $R = P+Q$ ?... |
Suppose you take the aes_sub_bytes function intended to operate on 4 aes blocks which were bitsliced to 8 u64's but you omit the bitslicing step beforehand. As a result you apply the sbox to the incorrect bits. But nevertheless the sbox is applied to all bits.
Do the security properties of AES change at all? You are no... |
Over a decade ago, a question was asked on Stack Overflow, which basically asked if there were any encryption schemes that are reducible to an NP-complete problem, in the sense that breaking the encryption implies breaking the underlying NP-complete problem, and hence proving $P\not=NP$.
As a concrete example, is there... |
My understanding is that for PAKE protocols such as OPAQUE (https://eprint.iacr.org/2018/163.pdf), the the adversary has no choice but to just do online attacks on the password. If this is true, I have 2 questions (which hopefully can be answered with references to RFC, NIST, etc.):
What is a reasonable entropy level ... |
I am reading this page on wikipedia on Key derivation function here where it states:
In cryptography, a key derivation function (KDF) is a cryptographic algorithm that derives one or more secret keys from a secret value such as a main key, a password, or a passphrase using a pseudorandom function (which typically uses... |
I have a scheme where a key and a data blob are provided that I need to decrypt. I do not know if the key provided is correct and I want to throw an error in my system if the wrong key is used.
I get no other information other than the key and the blob, so I want to put a magic string (8 bytes) at the beginning of the ... |
From Deterministic wallet:
A deterministic wallet is a system of deriving keys from a single starting point known as a seed.
From KDF from Wikipedia:
In cryptography, a key derivation function (KDF) is a cryptographic algorithm that derives one or more secret keys from a secret value such as a main key, a password, ... |
Following this page https://en.bitcoin.it/wiki/Secp256k1, secp256k1 curve's equation is
$$y^2=x^3+7$$
Does this mean that I can substitute $G_x$ in the equation to get $G_y$?
I think yes and that's how public key compression works, since we don't actually need to store $y$ value because we can compute it at run-time. B... |
So I'm trying to compare different digital signatures, and thus I stumbled upon a DSA algorithm. I'm using python's cryptography library, and it offers following values for L and N:
L=1024,N=160
L=2048,N=256
L=3072,N=256
L=4096,N=256
I'm wondering what are security levels of those pairs. I found this table from NIST ... |
Suppose we have A and B, e.g. a user a server, where A encrypts data to be processed by B homomorphically.
It seems that we could construct a pseudo-fully homomorphic encryption system---prior to Gentry's FHE scheme---where:
B processes encrypted data using additive (or multiplicative) PHE, then sends the encrypted re... |
So I'm trying to decrypt AES encryption with a 32-byte key. I know the first 7 bytes, and the final 19. I also have the plain text, as well as the IV and the encrypted text.
I'm currently running python code to try the combinations (for now I'm trying all the combinations of lower case letters), but I was wondering if ... |
I've got a comma-delimited list of identifiers that I need to use for uniqueness. MSSQL limits uniqueness to 1700 bytes, which according to my sampling, doesn't appear to be sufficient.
hashes are the obvious solution.
the identifiers are completely meaningless... they're lookups to locations of data... so there is NOT... |
I am trying to combine the effect the shift row and mix column into a single matrix. The cipher that I am working with is skinny64 (untweaked version). I know that combining the effect of these two matrices would generate a binary 64*64 matrix but I can't seem to figure out on how this such a matrix could be constructe... |
ElGamal cryptosystem provides multiplicative homomorphic property which can also be converted to additive homomorphic property. Can we use both properties simultaneously? For example, we want to achieve sum and product both simultaneously: E(a_1+a_2,...,a_n) * E(b_1+b_2,...,b_n), for instance, this could be achieved by... |
I've been reading about Learning with Errors here. On p. 7 there's a proof for the security of the PKE scheme, that goes through the leftover hash lemma, in order to prove that: $$ (pk, Enc(0))\equiv (pk, Enc(1)) $$ (Hybrid 2 and 3 there, for example).
I don't understand why we need that transition at all. Why can't we... |
Instead of sampling $\mathbf{s},\mathbf{u} \gets \chi$, we will sample $\mathbf{s},\mathbf{u}$ from $R_2$, i.e. the norm $||\mathbf{s}||=||\mathbf{u}|| = 1$.
$\cdots$.
The security implications of this optimisation seem to be minor, at least when we make the assumption that the results for the LWE setting carry over t... |
In Pinocchio paper, I'm confused by the equation in section 2.2.1. (image below)
Is the product of two polynomials $v_0(x)+\sum(cv(x))$ and $w_0(x)+\sum(c_w(x))$ of dot product or just a simple multiplication?
What I mean by the dot product of two polynomials is the multiplication of same-degree terms in each polynomi... |
AES-128 takes a 128-bit key (four 32-bit words), and expands it to a 352-bit key schedule (11 words). Speck48/72 takes a 72-bit key (three 24-bit words), and expands it to a 528-bit key schedule (22 words). Key expansion is an extremely popular practice, but I can’t figure out why.
Why not instead use a longer key with... |
I am refering to Privacy Aware Incentive Mechanism to Collect
Mobile Data While Preventing Duplication https://ieeexplore.ieee.org/document/7357616.
They claim to split secret $X$ into $X_s=\{x_0,\dots, x_n\}$ under a (2,n)-secret sharing scheme based on shamir's scheme, and compute $x_k'=\{x_k/X\}_{0\leq k\leq n}$ (in... |
I have a DER-serialized private key. The tool I have to provide the key to gives me algid parse error, not a sequence, and it looks like the problem is that the key is not PKCS#8.
The command that the most popular comment to the answer suggests, worked for me - I got a PKCS#8 key and the tool accepts it.
Now I am curio... |
It is known that by adding an extra round of communication, it is possible to convert a random OT (where the choice bits and the sender input are random) to a standard OT, see https://crypto.stackexchange.com/a/84206/48273 for details. OLE (oblivious linear function evaluation) is a generalization of OT. Specifically, ... |
I am developing an application in which all application state is entirely public. Each user of the application is equipped with their own ed22519 keypair, and the application can only ask users for signatures of arbitrary data.
I would like to store some private data for each user in the public application state. The p... |
As the question puts it: is there a test that can be done or a software that can be used, that is able to provide numbers/data to prove how secure a password hashing is? Say for example that I want to compare the security between using "phpass' portable hashes" and hashes made from "PBKDF2 using SHA3-512 as the HMAC" o... |
Given a polynomial-time adversary $A$ with binary output, the distinguishing advantage of $A$ with respect two games $G, H$ is defined as
$$
\newcommand{\adv}{\mathbf{Adv}}
\newcommand{\pr}{\mathbf{Pr}}
\adv^\textsf{dist}_{G,H}(A)=\left|\pr[A^G()=1]-\pr[A^H()=1]\right|.
$$
Where $A^G()$ denotes the adversary output whe... |
Given an encryption scheme that takes as input a key $k$ and converts it to an encryption operation $E$ via the function $M(k) = E$, is it possible that more than one $k$ can give the same $E$?
For example, let $k$ and $k'$ be two distinct keys. Is it possible that $M(k) = M(k') = E$. In this sense, the mapping from th... |
Nonces are often used to prevent replay attacks in networks. Because they are a one time use, any attacker replaying a request would be stopped because the nonce would be invalid.
However using nonces forces the serialisation of requests. Most web APIs are made to be usable concurrently.
Are there solutions that enable... |
I've been reading through MIT's lecture notes on learning with errors here, and I'm trying to understand the reduction from Search LWE to Decision LWE, as described there in Section 2.7, "Algorithm 1".
I cannot seem to understand why we need to repeat the sampling part (for guessing the $i$th coordinate and feeding the... |
I have to develop a program using a "secret" locally stored encoded program for a school project.
For this I have to decipher the code on the fly to use it. The project recommend the use of AES 256 in CBC mode, but for better performance any suggestion is welcome.
So I have two questions:
I made my own implementation ... |
I was reading up on the recently disclosed Hertzbleed side channel attack(s).
It was speculated on Twitter that the elliptic-curve cryptography library libsecp256k1 is not susceptible to these attacks. Firstly, is this true and why? Secondly, if it is true should these protections (e.g. blinding factors) be implemented... |
I'm reading the paper Improved OT extension. The author said that in semi-honest model, a single instance of $1$ out of n OT may be used to generate $\log n$ instances of $1$ out of $2$ OT. More precisely, the cost of $\text{OT}_{l}^m$ is exactly equal to the cost of $1$ out of n $\text{OT}_{l\log n}^{m/\log n}$.
I won... |
As per my understanding that the nonce of AES-GCM in SSL has 3 parts:
. salt, 4 bytes, generated in handshake, not changed in whole session
. nonce_explicit, 8 bytes, chosen by the sender and carried in each SSL record
. inner_counter, 4 bytes, used in AES-GCM internal
Question: I am not understanding that, what is ... |
Given a value $v = g^ah^b$, with $a,b$ secret, I was wondering whether there was a way to prove in zero knowledge that neither exponent is zero. In other words, given $v$ and $g,h \in \mathbb{G}$, I want to prove $\{a,b \in \mathbb{Z}_p: v = g^ah^b\wedge a\neq 0 \wedge b \neq 0\}$. I know how to achieve the first condi... |
From RFC 5246, section 6.2.3.3: AEAD Ciphers:
AEAD ciphers take as input a single key, a nonce, a plaintext, and "additional data" to be included in the authentication check, as described in Section 2.1 of [AEAD]. The key is either the client_write_key or the server_write_key. No MAC key is used.
I am not able to under... |
My book suggested the following protocol to replace SSL:
A lot of the terms are familiar to me from the Original SSL, like ChangeCipherSpec message which means from now on the messages I send will be encrypted. and FinishedClient: which is the first message to be encrypted.
But few things aren't clear for me:
Diffie-... |
In many cryptocurrency projects I noticed that 32-byte seeds/secrets are hashed to arrive at new 32-byte keys.
The reason why is because you can then, with the addition to an index, use the same seed to generate multiple keypairs/addresses/wallets under one seed/secret.
For example:
seed1 = hash(seed,0); // abc..
seed2... |
I'm so confused by this kind of exercise.
We have that $n = p * q$, where $p$ and $q$ are prime numbers. Let's examine this hash function:
$h(x) = x^2 \mod n$.
Determine if the hash function is pre-image resistant.
Can you have collisions?
|
I am here to ask a question on the current progress of private matching problem. Say, a user has a keyword (e.g. "apple") and a server holds a database of fruit records. Suppose the DB has the record of tuple (ID, name), e.g. (1, apple), (2, pear), (3, grape), and (4, orange).
The user wants to learn the following whil... |
I'm trying to implement impossible differential cryptanalysis on IDEA cipher based on the Miss in the Middle Attacks on IDEA and Khufu, I've started by implementing the cryptanalysis on 3.5-Round IDEA and in order to achieve this cryptanalysis I need an initial pair set of $2^{32}$ pairs.
I've written all the code fro... |
I was wondering what is typically the size of digital signature for every 1-bit data that is signed. I am trying to figure out how size of messages increases if I send only the data in a message or packet versus when I send the signed-data.
N.B. I am new this world of Cryptography, so don't mind if my question sounds t... |
I'm wondering if in public key infrastructure (PKI), a system user be able to set his public key without knowing its corresponding private key.
Can this be done?
|
I came across this scenario recently and would like to understand if there are any practical attacks against this implementation.
An RSA private key is used to "encrypt" data. The public key is included in a software component distributed to users and is used to "decrypt" this data. I'm aware that this offers no confid... |
I am looking to verify a card cryptogram sent from a smart card chip in accordance with SCP03.
According to the SCP03 spec, the CMAC is used to generate a MAC to authenticate messages sent to/from the secure element.
The SCP03 spec says that AES in CBC mode is used to do encryption and decryption, but it is unclear wha... |
I am working on Victor Shoup's tutorial on game-based security proof and want to figure out some notions from the perspective of probability theory.
Consider the following PRF advantage defined on Page 11:
$$
\bigl|\,\Pr[s \leftarrow S: A^{F_s}() = 1] - \Pr[f \leftarrow \Gamma_{\ell_1, \ell_2}: A^f() = 1]\,\bigr|
$$
wh... |
Alice is using AES256 in CTR mode to send encrypted messages to Bob. The messages are 4 byte values. Along with each encrypted message, Alice sends along a random 16 byte IV. f maps a 4 byte value v to the 16 byte values v|v|v|v (concatenates it with itself 4 times). Would it be secure for Alice to randomly generate 4 ... |
There is a handful of attacks against AEAD, and GCM in particular, which demonstrates that it is feasible for an attacker $\mathcal{A}$ to obtain a ciphertext $C$ which encrypts to multiple key/message pairs $(k_i, M_i)$.
This is commonly referred to AES-GCM not being key-committing.
Now, I'm a bit confused about the n... |
Though there are many papers available on application of Simon's algorithm for symmetric encryption, nothing is clear on implementation - like how to build the oracle, how many PT-CT combinations are required, what exactly is the hidden string 's' (key or just difference between two messages). Can anyone please explain... |
I am working on a smart-contract to be deployed on ETH chain.
I am using an oracle(not the company!) system to get the information from off-chain (outside of the blockchain). Basically, we can think of the oracle as an API call which returns a random number. But for this api call I need a random seed.
Questions:
Can I... |
The question is mainly stated in the title. I am new to lattices and I have a basic understanding of them but not something in depth. I was watching a presentation of of a VSS (Verifiable Secret Sharing) scheme that was using lattice based encryption and they mentioned that "We are using lattice based encryption which... |
When it comes to stateful schemes, would you really need to use a Merkle tree?
Couldn't you sign the hash of the message concatenated to the hash of the new public key?
New public key: hash(hash(message) || hash(WOTS+/lamport public key))
Then for every new signature you include the previous signature(s) (without the m... |
I want to store two ciphertexts inside the same file.
The data stored in each ciphertext is the same (except for padding), but the data was encrypted with different keys and IVs. Both ciphertexts were also generated by the same algorithm.
In this case specifically that would be a variant of AES, Chacha20 or Serpent.
In... |
Can somebody lead me to existing literature on making the extraction of plaintext dependent on a valid signature check first? I didn't think it was possible to force signatures to be checked; but this is possible, and I have an implementation of it with RSA.
For background: I have been following the multiple problems w... |
According to this question, I found papers that deal with noise flooding with Renyi divergence. However, the answer is still unclear to me on how to use Renyi divergence on the noise flooding technique.
For example, Section 5 in this paper provide a tight analysis for noise flooding by only showing $RD_2 (\chi_\alpha +... |
For signatures, there is the security goal of existential unforgeability. As seen here and noted here (german source) the security goal can be split into weak and strong unforgeability for chosen message attacks.
As far as I understand it, the difference between strong and weak is having a completely arbitrary message ... |
In https://tools.ietf.org/id/draft-stebila-tls-hybrid-design-03.html, they define (many other sources do too) hybrid shared key exchange as
“Hybrid” key exchange, in this context, means the use of two (or more) key exchange algorithms based on different cryptographic assumptions, e.g., one traditional algorithm and on... |
I'm currently reading the book "A Pragmatic Introduction to Secure Multi-Party Computation". On pages 103-104 I came across the following related to the Cut-and-Choose technique:
If $P_2$ sees inconsistent outputs, then it is obvious to $P_2$ that $P_1$ is misbehaving.
It is tempting to suggest that $P_2$ should abort... |
I know this seems a bit contrived, but I’m a layperson to cryptographic systems and have been trying to think if it’s possible to devise a scheme where it’s possible for a sender to prove, in a public key cryptosystem, that a given ciphertext was encrypted with a given public key, without significantly weakening the se... |
Rand48 is a pseudo-random generator which produces a sequence of any given integer using the following rule:
$a_n=(25214903917 \cdot a_{n-1})\bmod 2^{48}$.
If $b_n=\lfloor a_n/2^{16} \rfloor \bmod 52$, the sequence $b_0, b_1, \dots$ becomes an infinite string called $c=c_0, c_1, \dots$ to the following rule:
$0\to a, 1... |
With a Sponge permutation in a Duplex construction for authenticated encryption.
illustration example: ascon; actual interest if relevant: keccak
Suppose there is no associated data and there is no nonce, just a key.
A classical xor-cipher problem arises with the first cipher-text block where
$C_{a,1}\oplus C_{b,1}= P... |
I am an industrial biotecnologist from Italy. I am very interested in computational complexity and in protein folding problem in particular. I have a question. Hash functions are functions that given a slightly different input generate a very different output and are practically impossible to reverse. Is there a parall... |
Since the Set Cover Problem is an NP problem, Zero Knowledge System for Set Cover will definitely exist, but I cannot find such a proof system.
|
The Groth16 is the zero-knowledge proof scheme,I want know what is the time complexity of Groth16，including generate proof and verify proof.Thanks.
|
I would like to publicly store a list of public keys of recipients in a way that only the individual recipient ( who holds the private key of a that referenced public key) can see that he is referenced in that public key list and preferably not be able to see who else is being referenced.
This means the list of recipie... |
Context: Many widely used public-key cryptographic schemes have been designed based on the difficulty of factoring and similar problems. That includes RSA, the Diffie-Hellman Key Exchange, ECDH, ECDSA, Ed448, Ed25519.
This includes almost all cryptocurrencies.
Even though NIST may not be fully ready, some of us (espec... |
Working in security, I often hear terms such as algorithms, ciphers, primitives and functionalities. but as cryptography is not my field, they seem to be used interchangeably.
What are the differences between all those terms, and what nuances do they bring?
|
I believe I know quite well OPE and ORE, but I'm unsure about what family to put them in. Can we consider them as a sub family of Functional Encryption, like Attribute Based Encryption or Inner Product Encryption or are they a new paradigm of their own ?
|
I answered a question on StackOverflow yesterday that was asking why the following keyless encoding/decoding scheme for 16-bit numbers worked:
Encoding
Note that the "shift" operation is a rotational shift, not just an arithmetic shift.
Note also that I am using $\oplus$ to indicate a bitwise $XOR$ operation.
$$ L(... |
I've been studying the OPAQUE protocol, and I like it (so far).
The RFC suggests using Argon2 as the Key-Stretching Function. Argon2 can take an optional "Secret value" (2, page 5).
I had the idea that that secret value could be provided by a Yubikey, so that the resulting OPAQUE protocol could use "something you have"... |
I have a version D TR-31 keyblock (which contains an AES Key for use in CMAC), and have the ZCMK key used, what is the method which I can use to extract the key from the TR-31 keyblock? I'll do my own development.
|
I would like to ask you about what I think is a variation of BB'06 signature forgery¹.
Unlike BB'06 where the forged signature is valid for any pkey with e=3 the one I have is valid only for one pkey. Interesting in it is that out of the 128 bytes long signature the first 85 bytes is actually part of the pkey that I us... |
Based on How does SafeNet MobilePASS generate passwords?, I'm not sure if the MobilePASS token can be extracted for use in another TOTP app such as andOTP or KeePassXC. (I guess it depends whether the MobilePASS algorithm is a standard one.) Is this possible? If so, how? Can I use the activation URL (so I don't even ha... |
Given public generator $g$ of some cyclic group, a secrets $x\in Z_q$, and public pairs $(a_1,b_1),...,(a_n,b_n)$ (where $a_1,...,a_n$ are selected at random from a big set), and prime p, that satisfies the equations $g^{x^{a_i}}\equiv b_i\ (mod\ p)$ for all $i=1,...,n$.
Is it hard to compute to compute x (assuming the... |
This problem was posed during a recently ended contest.
I am given a value for n and e. e = 65537. n is a 2048-bit number.
p is a 1024-bit prime number.
q is the modular inverse of e mod p. That's the mistake made in this
problem. q is also non-prime.
Can I use this knowledge to simplify my calculation of the totient... |
If you have an RSA keypair (n,d,e), and you don't publish n to the world, how many bits of security is that? For example, if I get a set of messages signed with the keypair, can I guess n ?
I have to consider this for a real practical problem. I am trying to replace the JWT scheme with something that is more fool-proo... |
I have read that the Germans used to encipher a random three alphabet word chosen by the operator twice and put that before the enciphered message.
What purpose did that have and what key they were using to encipher the random three alphabet word?
|
As part of a reduction I'm trying to construct, I want to show that the two terms described at the bottom are identically distributed, but I'm not sure if this is correct and I cannot seem to prove that it is formally. I was trying to formulate my reduction similarly to MIT's reduction at the top of p.5 of this pdf.
De... |
Recall that the LWE problem is the following.
LWE problem. Let $q$ be a prime, let $\chi$ be a distribution of small elements over $\mathbb{Z}/q$, and let $n,m$ be two integers (dimensions of vectors that we work with). Sample $s \leftarrow \chi^n$, $e \leftarrow \chi^m$ and $A \leftarrow \mathbb{Z}/q^{m \times n}$, w... |
Suppose $m$ is the message that the Eve attacker wants to sign with the RSA signature scheme with the public key $(n, e)$ and the private key $(n, d)$. Suppose the signer Eve is given oracle access to the signing algorithm for any other message such as $m'$, where $m'$ with $m' \neq m$. How can Eve calculate the signat... |
Let $E$ be any encryption algorithm, and consider the following game capturing key reuse.
Alice samples a key $k$
Bob sends a set of messages $\{m_1, ...,m_n\}$ to Alice
Alice flips a coin
if heads Alice encrypts all messages with $k$ and sends the ciphertexts to Bob,
if tails, for each message $m_i$ she samples a k... |
Assume that we have (know):
Hash(A)
Length of A
A's character type ([0->9],[a->z])
A is a string
Everything about B (original string, Length, etc.)
HashMethod SHA256
Note: A's original value is unknown
Is there a way to use that information to create Hash(A||B) [|| is concatenate {"a" || "b" -> "ab" for example}]
|
In ECC, the proof showing that given $G$, $x$ and $y$ is in the range $[-z,z]$ is known as the range proof.
Related to: Proving that two points on elliptic curve are within range
So, if:
$$H=xG−yG$$
it is possible to prove that $x−y$ is in the range $[−z,z]$.
Could you explain how to apply this theory? Do you have a re... |
Given a secret key x and a commitment to it comm(x) where comm(x) is both binding and hiding (it can be for example $g^x$ or some homomorphic encryption). Given public parameters $P_1,...,P_k$, comm(x), and an index i, is there a scheme, other than fully homomorphic encryption, to to compute $H(P_1,...,P_{i-1},x,P_{i+1... |
In most FHE schemes, for a polynomial $m_1$,
$$enc(m_1) = a_1*s + e_1 + m_1$$
Suppose I have $enc(m_1),enc(m_2)$. Can I subtract them exactly? Sum works, but subtraction is:
$$enc(m_1) - enc(m_2) = (a_1-a_2)*s + e_1-e_2 + m_1-m_2$$
In the case where $e_1-e_2$ is negative, this gives us problems in the decryption (clean... |
Verifiable computation (VC) has been practical since Pinocchio and the field has evolved significantly since.
What are some of the best examples today where computation is significantly faster than the verification, for VC to make sense? Are there examples where computation is astronomically slow, but verification is l... |
I'm new to making applications that encrypt sensitive data and so don't know where to start.
My question is what is a good encryption scheme that can be run in a good time for normal application and is secure?
I would really like one symmetric and one asymmetric method but would settle for symmetric.
|
I've found this task in the "Introduction Mathematical Cryptography by Jeffrey Hoffstein":
The guidelines for choosing NTRUEncrypt public parameters (N, p, q, d) in-clude the assumption that gcd(N, q) = 1. Suppose instead that Alice takes q = N ,
where as always, N is an odd prime.
(a) Make a change of variables x = y ... |
In a Korean examination, the correct answer was "Cipher feedback mode is known to be susceptible to replay attacks". But when I read the Wikipedia page, it only mentions that for the ECB mode. Is cipher feedback mode also susceptible to replay?
|
With One-Time-Pads I have heard that it is preferential to use XOR because the ciphertext reveals no information about what the plaintext may have been (for each 0 and 1 of the ciphertext there is a 50% chance that the plaintext was a 0 or a 1).
In contrast AND means that some information is revealed about the plaintex... |
Reading paper: ‘even s. A randomized protocol for signing contracts [J]. ACM SIGACT news, 1983’, there has been a question why this scheme cannot be directly extended from 1-out-of-2 OT to 1-out-of-n OT. The OT extension in the later paper adopts very complex methods to expand.
Brief description of the original scheme:... |
Hi I am totally new to cryptography.
This paper [1] was explaining the mix columns. But at a point I am not understanding the calculation.
F2 * 03 = F2 *02 + F2 * 01
= 1111 0010 *02 = 11100101 XOR 1B = 11100101
XOR 0001 1011
F2 *02 = 1111 1111
how come 11100101 XOR 00011011 = 1111 1111 ? isn't it 1111 1110
Can anyone e... |
Checks for null require an == check. If you have a string secret (say a hex-encoded key) and you want to check it's empty for validation should you compare it to "" in constant time?
You don't hear about constant time equals in these cases.
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