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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.
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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.
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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.
|
As for the PQC algorithm Saber.PKE based on M-LWR, I wonder whether it supports homomorphic addition operation. According to my related work, the error of this algorithm can be written as $e_S = ||s^{\prime T}e-e^{\prime T}s +e_r||$, this fomula satisfies$e_S \mod p < p/4$. By parameters selecting, whether we could con... |
Is following approach secure?
Planning on using implementation to XOR two passphrases before feeding result to Argon2.
const xor = (a: string, b: string) => {
if (a.length > b.length) {
b = `${b}${b.substring(0, a.length - b.length)}`
} else if (b.length > a.length) {
a = `${a}${a.substring(0, b.length - a.... |
I encountered the following scenario in development of a system.
A user wants to perform an operation on one of $n$ days. An adversary can observe a sequence of integers $X_1, \cdots, X_n$. If the user performs the operation on day $i$, then $X_i$ will be sampled according to distribution $Q$, while all $X_j(j \neq i)$... |
I'm looking for a Additive Homomorphic Encryption scheme which can allow a ciphertext of size smaller than 128 bit.
I started studying this topic very recently so I don't have much knowledge, but I checked on Paillier and RSA and found out for 2048-bit RSA the ciphertext size is 2048 bit and for equivalent Paillier sch... |
I have been looking at the Galois/Counter Mode (GCM) for stream encryption. I understand the idea that it's a stream cipher and so it can be encrypted one bit at a time by XORing with the key stream and how this is better than something like CBC because you can start anywhere in the middle of the stream without calcula... |
A prover has a secret exponent $x$, two public bases $g$ and $h$, and a public RSA modulus $N$ of which no party knows the totient/factors. All inputs other than $N$ are coprime with $N$ with overwhelming probability. She publishes $a = g^x\bmod N$ and $b = h^x\bmod N$, but she needs an NIZK that she used the same expo... |
How to determine if an elliptic point $kG$ is negative? Is $k<0?$
By example, for $k=1234$, the coordinate of the point $1234G$ using secp256k1 =
$X= 102884003323827292915668239759940053105992008087520207150474896054185180420338$
$Y= 49384988101491619794462775601349526588349137780292274540231125201115197157452$
Note: $... |
As an example, let's take a simple situation where AES-256-CBC with IV + MAC is used to encrypt a given plainText to offer both authentication and prevent identical cipherTexts.
iv.mac1.cipherText(plainText)
The keys are derived using HMAC for simplicty (alternatively could be HKDF)
masterkey = [32 random bytes];
encr... |
As an example, let's take a simple situation where AES-256-CBC with IV + MAC is used to encrypt a given plainText and offer authentication.
iv.mac1.cipherText(plainText)
The keys are derived using HMAC for simplicity (alternatively could be HKDF)
masterkey = [32 random bytes];
encryptionKey = hmac_sha256(masterkey,'en... |
I have read/write disk images encrypted with 128 AES using Mac's disk utility. If I snapshot the encrypted disk images daily (sometimes with changes other times without), and an attacker has access to these snapshots, will they be able to gain any parts of the plaintext? Will they be able to gain any metadata about the... |
It's been a while since I know about cryptography, and always end up seing diagrams like this.
However I have never been able to understang their meaning. I hope someone can explain in detail. Thank you in advance
|
For data integrity, specifically for small blocks of data, rather than using a SHA-256 hash, or simply truncating a SHA-512 hash, I am playing with the following idea:
function saferHash(data) {
let hash1Entropy = 42; // sha512:42
let hash2Entropy = 4; // 4B extra possible protected outcomes in case of highly ... |
Why most of Lattice based scheme use Montgomery Multiplication algorithm?
|
I'm reading the paper Extending OT. In the extending OT protocol, the sender using $H(j, \textbf{q}_j)$ as the mask, why not use $H(\textbf{q}_j)$ directly?
|
I noticed some new quantum cryptography algorithms are being developed.
I know very little about quantum computing but my understanding is that it will just be a much more powerful computer and therefore all the current key sizes that we use for cryptography will be rendered vulnerable to brute force attacks. Maybe the... |
I am trying1 to build a Proof Of Concept of a e-voting scheme on a blockchain. Before the elaboration, the question:
On a public e-voting, how do I keep the votes from being disclosed prematurely without a trustee?
The project works the following way:
Noone trusts noone4, so no trustees at all.
A "blockchain" here is ... |
I want to evaluation following functionality:
Parties have secret shares of private input [a] and public input b, they want to measure if
a>b, additionally only one party should learn the output
I know this could be directly done with millionaire problem solutions such as:
CrypTFlow2: Practical 2-Party Secure Inferen... |
Since the maximum authentication tag (MAC) size of AES-256-GCM is 16 bytes,
And given that in one implementation, that breaking the MAC would break the security (ex. when a boolean 'decrypted' is used to either deny or allow access),
Would using an additional MAC within the cipherText be a good idea or is this over-eng... |
Suppose I have a dumb password checking function:
def dumb_checker(password):
return password == "my_secret_key_that_should_not_be_revealed"
One can hide a password by hashing it as follows:
def obfuscated_checker(password):
return hash(password) == PRECOMPUTED_HASH_OF_MY_SECRET_KEY
which means that the indis... |
I was wondering how "IPS" systems process and react to the AES encrypted data than the DES
|
If you alter the SPHINCS+ signature scheme such that the number of signatures it can sign is the same as the number of hashes the hashing algorithm can output such that for example if you have a 2^256 hash SPHINCS+ would be altered to be able to sign 2^256 messages.
Would you then be able to remove any requirement for ... |
I am planning to use AES-GCM or AES-CTR for encryption. However, I have read from several sources that the IVs must be unique for every piece of information encrypted. I have a doubt though, what if I choose different IVs for the two encrypt calls, but the counter addition makes the IV+counter value the same for some o... |
Trying to figure out how the scheme works I came across the last paragraph of the page. As stated, for any possible additional factor we multiply by the specified power v of the element g. How did this "possible factor" showed up? Even so, why multiplying with the specified power v of g solves the appearance of such f... |
For what I know from the RSA algorithm, the receiver of an encrpyted message needs the Euler totient to generate its private decryption key. If the sender has chosen two primes p and q, then the Euler totient could be $(p-1)*(q-1)$ which is a value needed for the receiver. In this case, how the Euler totient is shared,... |
I’m new to development using web3 technologies and I have a use case where I want to store private data about the user in the public blockchain Polygon.
This data should be recorded to be tamper proof and indisputable, however I also want to protect users privacy. This is why I came up with an hybrid solution I will di... |
Do there exist information theoretic secure public key crypto-systems? Are they useful in any way, or are they just mathematical curiosities?
|
I was learning about bitcoin cryptography and seen some strange bitcoin public addresses like this
1Lets1xxxx1use1xxxxxxxxxxxy2EaMkJ
1fuLL1xxxx1power1xxxxxxxxxxzatvCK
1of1xxxxx1anonymity1xxxxxxxz9JzFN
how someone can derive this kind of addresses from private key? and if it is possible somehow does it gives chance to... |
What is the signature size of Natasha Otomoski haircomb? What is the number of invocations of the underlying one way hash function for key generation, signature, and verification?
How does it compare to the recently standardized variant SPHINICS+?
|
I've been in my PhD program for a few months, and every time I try to understand the simulation and UC proof-paradigms I get so confused.
I feel like what I really need is an easy set of (guided) problems and examples that I can play around with and try to prove, starting with non-composable simulation and then moving ... |
I am a developer with very little experience on the crypto part,
and I'm looking for a secure solution (OTP Like) for identifying between client (browser) and server.
this is what i need:
Web Page at 10.00 AM generate a randomly id based on a secret key
User A
10.00 AM 258e461ba8b7b66a02cf17dfe60f465c103c742e570f492a31... |
The use-case is as follows:
There is a signer, call it $S_A$ that have a claim or document $D_j$.
$S_A$ wants any client $C_k, \forall k$ to be able to verify that it has not been tampered with.
I suppose one way to do this is to use assymetric encryption where $S_A$ encrypts $D_j$ as: $E_j = encrypt(D_j, K_{priv})$ us... |
What (obvious) security issues does the following "onion" Distributed Shamir Secret Sharing scheme on a blockchain for the purpose of e-voting have?
The blockchain in this context, is an immutable ledger of records, where any known identity can add a record. Authenticity of source of the records, the privacy of the vot... |
My bank seems to use something like HMAC-based one-time password, and it generates a new code every time I open it, and I could in theory skip a thousand codes (not use them to log in), and then the counter event value would have skipped forwards a thousand for the bank when they try to verify my hash.
I am interested ... |
In the paper describing a protocol for distributed RSA modulus generation, Diogenes, "[they] employ a special-purpose $\Sigma$-protocol based on [Sho00] for proving correctness of exponentiations in a hidden-order group."
If it says this explicitly I haven't found it, but I am assuming the hidden-order group is the $\m... |
In LWE, we know that given reasonable public parameter $A\in \mathbb{Z}_q^{n\times \lambda}$, secret $s\in \mathbb{Z}_q^{\lambda}$ and noise $e\in \mathcal{X}^{n}$, random $r\in \mathbb{Z}_q^{n}$, $(A, b = A\cdot s + e)$ and $(A, r)$ are computationally indistinguishable.
Then, consider another scenario that $A$ is sam... |
Let SE be stateful encryption.
Then, it is well known that the oracle for the security proof becomes stateful too. (We only consider the IND-CPA security game.)
On the other hand, assume that E is stateless encryption.
Then, can the challenger for proving the IND-CPA security of E behavior as astateful encryption schem... |
Although Goldreich-Godlwasser-Micali (GGM) construction of a pseudo-random function (PRF) from a pseudo-random number generator (PRNG) is widely in many cryptographic applications, it needs to consume $2n^2$-bits of PRNG output to generate $n$-bits of PRF output.
Can we make it more efficient with other structures but ... |
I am developing a web application in which each user has some part of his data that is stored encrypted. We are hosted on AWS and I want to use KMS as part of the solution. To not make the solution overly expensive (AWS charges per key) I was thinking of the following solution:
I generate 1 RSA master key in AWS KMS
F... |
Suppose Alice chooses a number $n\in Z_q$ and decompose it to its binary representation $b_0,b_1,...,b_d$. Then Alice encrypts these bits (can be any encryption scheme). Is it possible for Bob (who does not have Alice's decryption key) to read these encrypted bits and create a vector of size $q$ so that each entry is ... |
I understand that you can't discern a private key from a public key, but what if you have thousands of examples of the private key signatures, and you know what the message/cypher is?
Basically, you can't do the hard problem with no clues, but if you have clues (thousands of examples of signatures from that private key... |
Ligero (https://dl.acm.org/doi/10.1145/3133956.3134104) and Limbo (https://eprint.iacr.org/2021/215.pdf) use a somewhat unique MPC model for their zk-PCP where not all parties communicate with each other.
Briefly, in their model there is a sender $P_S$, $n$ servers $P_i, i \in [n]$ and a receiver $P_R$. The protocol be... |
In his paper on pairing based cryptography, Menezes claims that for
$$
E_1: y^2+y = x^3+x+1
$$
the number of $\mathbb{F}_{2^m}$-points is $2^m +1 - (1+i)^m - (1-i)^m$. Whereas this is clear, it is not clear to me how he reaches this conclusion:
In addition, I also do not see why it is relevant (and how one sees/arrive... |
If I have a linear (7,4)-Hamming Code I know that the last 3 bits are the parity bits but I just have seen that there are multiple linear codes like (7,3) for example the code with basis:
$$\begin{bmatrix}1 & 0 & 0 & 1 & 0 & 0 & 0\\
1 & 0 & 0 & 0 & 0 & 0 & 1\\
1 & 0 & 1 & 0 & 1 & 0 & 0 \end{bmatrix}$$
(!Notice that it'... |
Is there any cryptographic method for Proof Of Computation ?
If i am running my program on untrusted hardware (remote server), after some time i want to verify the remote machine hasn't tampered with my program and successfully ran it for required time (and the result/output is correct), how can i verify ?
Is there any... |
I have a question regarding William Wang's paper Shorter Signatures from MQ. According to him the (maximum) signature size is:
$$
2\kappa +
3\kappa\cdot \lceil\tau\log\frac{M}{\tau}\rceil
+
\tau\cdot\left(
\kappa\log N
+ 2 \kappa
+ (n+m)\log q
\right)
$$
The parameters can be chosen in a variety of ways, in the paper t... |
I was sent from Stack Overflow to here (original question). I'm quite new to cryptographic programming. I want to generate TLS certificates on application boot up time. It is a Spring Boot application, therefore Java and that means I'm using Bouncy Castle. Right now I have to decide, what the default algorithm would be... |
2 requirements of Byzantine broadcast (consistency and validity) only state honest node should output certain bit without mentioning what should malicious nodes do.
How do we know the identity of each node?
Could I distinguish honest and malicious node by checking the majority of vote (honest nodes is majority) assumi... |
All examples I find on SNARKs show polynomials of up to degree 3 or 4 but what about polynomials of degree over 5, what is the mechanism that allow SNARK not to be affected by the unsolvability of the quintic while calculating roots? Is there a high degree polynomial example that I could read?
|
I am trying to unscramble received data packets. Each packet is divided into 3 parts ($A$, $B$ and $D$) with equal lengths. In every packet, each of these parts are scrambled/encrypted with an unknown code $C_i$.
We can tabulate these received packets in the format shown in the table below, where $\oplus$ denotes the X... |
Suppose the tuple $(P, a, Q)$ is given, where $P$ and $Q$ are points on an elliptic curve (I'm more interested in Montgomery curves but other curves are also fine), $a$ is a scalar and the notation $[a]P$ is the scalar multiplication. Is there a way to quickly check whether $Q = [a]P$? Specifically, is there a way to d... |
I recently needed (for legitimate reasons) to crack an encrypted pdf sent by a local bank. It was pdf1.7 and the password was 6 digits. cracking it with John the ripper took no time at all. In fact it was faster than normal waiting for the SMS, which is the way I should have gotten the password but that wasn't working.... |
My use case, making public-key encrypted backups, requires deterministic public-key authenticated encryption. I favour NaCl box, but the way it is generally used is probabilistic and it yields different ciphertext due to the random ephemeral Curve25519 key used in the computation of the shared secret. I am wondering, i... |
NIST selected Kyber for key agreement and Dilithium for digital signature applications some days ago. But IDF's MATZOV group, in their paper, broke Kyber and Dilithium and brought the security levels of these schemes below the thresholds defined by NIST for a secure PQC scheme.
Why did NIST not consider MATZOV's attack... |
Maybe the below question is similar to what I was thinking, but I don't understand:
Is BLS signature scheme strongly unforgeable?
Below is the attack method I was thinking of. If know m, can't create a new signature from it?
sk is secret key
pk is public key
m is message
S is signature
e(P, Q) : bilinear pairing
Sign... |
Considering an HMAC algorithm: it shall guarantee integrity and authenticity. I don't understand what authenticity means: that signature could be generated by anyone having the shared secret key (non repudiation is not supported in symmetric crypo-algorithms). Then why could that message be considered authentic if it c... |
I wrote SHA-256 with arrays of integers representing the bits (e.g. [1,0,...,1]), and then I altered it to accept partial values (e.g. [0.5, 0.79, 0.0, 1]), as in each value has an x chance of being '1' and a 1-x chance of being '0'. The hope was to be able to change my input by less than 1 bit at a time to violate the... |
Does GCM spec (NIST SP 800-38D) require tag-size to be fixed for an instance of GCM algorithm (which usually fixes a specific GCM key)?
Asked differently, is the following a legitimate adherence to GCM spec?
There is a discussion going on on GitHub - perhaps knowledgeable folks could comment.
// pseudocode
var one_gcm ... |
If x is the value you're hashing, $t(x)$ is the hash of that value, and $t(x+s)$ is that value with salt, then hashed. You could create a hash table where the key is $t(x+s)$, the value is $x+s$, and compute then store all of the possible strings with a length less than $n$ characters.
If you cracked 2 hashes by guessi... |
In NIST SP800-107, NIST claims that the security strength of HMAC is MIN(security of HMAC key, $2L$). $L$ is the length of the output of the underlying hash function. Let's take HMAC-SHA256 as an example. If the key used is larger than 512-bits, it is truncated to $L$ bits, which is 256-bits. However, if the key is sma... |
So I've been working on a project that aims to allow online distribution of one-time-pads securely. I understand that a pad cannot be reused and must be truly random, and that if it is compromised, the message can be read. The problem is that each pad has to be transmitted in person. I was wondering if this can be done... |
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