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Given a random 256bit key used for data encryption with Streaming AES GCM
I would like to wrap it for backup with AES GCM.
Is it safe to use
HKDF(
km = new random 256bit key
salt = Argon2(weak password) 256bit
algo = HMACSHA512
outputkey = 256bit )
in theory the km parameter has to be stored safely off... |
I'm trying to understand CKKS (non bootstrappable) and I'm struggling with the encoding part. Particularly with to questions.
I'm using the original paper , "Homomorphic Encryption for Arithmetic of Approximate Numbers
", also this notes "Lattices, Homomorphic Encryption, and CKKS"
and this blog.
Given a vector $z\in \... |
I have some troubles with this proof from Foundations of Cryptography by Oded Goldreich p.52.
Why exactly does the parsing of x to x'x'' take quadratic time in length x'x''? If I have |x'x''|=p(|x'|), and a x of this length. I will try step by step all prefix lengths |x'| in {1, 2, ..., |x|}, till I have p(|x'|)=|x|. S... |
How many timestamps are issued when someone signs a PDF with timestamp Long Term Archive (LTA)? Why is it necessary to issue more than one timestamp?
|
TL:DR I'm learning RSA. I've made it to the decryption stage but I don't know how to handle huge exponents. These are my values:
p = 17
q = 31
e = 7
m = 2
n = 527
(n) = 480
de = 7(343) = 2401
d = 343
PU = {7, 527}
PK = {343, 527}
C = 128
So I'm unable to handle the processing of the decryption of Cipher text 128, wi... |
I am trying to solve this problem from https://toc.cryptobook.us/book.pdf.
I am having trouble with this question :
(Baby Bleichenbacher attack). Consider an RSA public key (n, e), where n is an RSA
modulus, and e is an encryption exponent. For x ∈ Zn, consider the predicate Px : Zn → {0, 1}
defined as:
Show that by q... |
I've been reading lately some contradicting messages with regards to the quantum-safe resistance of AES128. First, there are blog posts by Ericsson people like these ones:
Can quantum attackers break AES-128?
No. NIST estimates that a quantum computer breaking RSA-2048 in a
matter of hours could be built by 2030 for a... |
When I'm convincing non-believers that crypto is secure, I have a hard time with hash functions and the associated block ciphers.
It is easy to show why RSA is hard to crack: I multiply two small primes and ask people to factorize the product. They find it difficult compared to the multiplication step.
It is easy to sh... |
Yesterday IBM announced that they have a 433 bit quantum computer, called Osprey. There is nothing in the press releases I can find that says whether it can or cannot run Shor's Algorithm.
They also say they are on track to release "Condor", an 1121 bit processor next year.
Shor's algorithm, as far as I know, requires ... |
I'm working on this past exam paper and found this question about pre-image resistance and its relation to data integrity:
Displaying the hash of a file on a website in order to provide data integrity relies only
on the preimage-resistance property of the underlying hash function. Is this true or false?
I answered fals... |
I'm creating a mobile chat application using python (django) as backend, and I'd like to implement an end-to-end (E2E) cryptographic system for protecting messages.
Now, as I understood so far, when one of the user create the chat, the server will go to generate 2 couples of public and private key, and the next step is... |
So I'm currently working through this cryptography question and so far I have the answer of an increase of hackers due to increase in computational power. But apart from that I don't know what else. Number spoofing? Weaker security mechanisms in organisations? Not really sure apart from the computational power increase... |
I am currently studying the Kyber Paper. I have a question about section 2.2 Compression and Decompression, but first I would like to quote the statement:
Compression and Decompression. We now define a function
$\text{Compress}_q (x, d)$ that takes an element $x ∈ \mathbb{Z}_q$
and outputs an integer in $\{0,..., 2^d ... |
I have a CBC-MAC scheme using AES as the block cipher (T=H_K1(M)), which gives me a tag and a stream cipher using another key and a nonce, which gives me a cryptotext (C=E_K2(N,M)). So my question is based on a known-plaintext attack to create a valid (ciphertext, nonce, tag)-tuple.
I already figured out how I can crea... |
Suppose you have two files encrypted with AES-256. One of the two files is 5MB, the other one is over 1GB. Their passwords are reasonably strong: >12 characters, letters, numbers, upper and lower case characters. If you tried to brute-force them, would it take a shorter time to try the same number of passwords on the s... |
Here is my idea:
Under the symmetric key encryption. Alice and Bob share the symmetric key K. Let HASH be a secure hash function and Enc_k(message) be the encryption message m by AES in the CBC mode with a random IV
First, Alice compute c = Enc_k(message)
Second, Alice compute t = Hash(m)
Third, Alice sends (c, t) to B... |
I am reading the paper A Concrete Security Treatment of Symmetric Encryption and am confused by the reduction from ROR to LOR on page 11. Specifically, when it says:
When $\mathcal{O}_2(\cdot)=\mathcal{E}_K(\mathcal{RR}(\cdot,0))$, we have that $\mathcal{O}_1(\mathcal{LR}(\cdot,\cdot,0))$ and $\mathcal{O}_1(\mathcal{... |
I am having a university assignment that requires me to study on the threats that quantum computer poses to modern cryptography.
At the moment, I know that modern symmetric encryption will reduce their key size strength in half through Grover's algorithm. It can also break existing standardized RSA, Curve448 and Curve2... |
As far as I know, key exchanging algorithms are vulnerable to an active MITM attack.
Let A (Alice) and B (Bob) be parties with no secret information. An adversary C
playing man-in-the-middle interacts with A pretending to be B, and
interacts with B pretending to be A. At the end, C establishes a
separate channel with ... |
Suppose Alice has a verifiable (message, signature) pair from Cedric, who would not cooperate and routinely uses an algo (ecdsa, eddsa, rsa, or insert yours here) to sign messages.
Alice wants to interactively prove to Bob she has that (message, signature) pair with the valid signature, obviously. It doesn't have to be... |
I've recently become interested in homomorphic encryption, specifically how boolean gates are constructed to do arbitrary circuit arithmatic on the encrypted data without decrypting it.
I have heard that all you need are arbitrary addition and multiplication operations to arbitrarily construct boolean gates that can op... |
Given the following code, extracted from a Bip39 implementation for Android by Zcash
PBKDF2SHA512(
passphrase = veryHighEntropy secret bytearray,
salt = pontentiallyLowEntropy secret bytearray,
iterations = 2024,
)
What happen if the passphrase gets leaked? is the total entropy of the hash reduced to the e... |
Problem example
Let's say I have a plaintext with length of 50 bytes. I want to encrypt it using a stream encryption algorithm ChaCha20-Poly1305.
Poly1305 generate a 128 bit hash (16 bytes), so encrypted message will be of length 50 + 16 = 66... If I append nonce to it (12 bytes), it'll be 78 bytes.
But... When I add f... |
Suppose there is a ciphertext $C_1$ that hides message $m_1$ using a distributed additively homomorphic public key. I would like the holders of the key to run a protocol where if $m_1 = 0$, then it will return a ciphertext of $0$, but if $m_1 \neq 0$, then it will return a ciphertext of $1$. However, I would like thi... |
I am trying to understand digital signatures and digital certificates. I know that digital certificates verify a server's public verification key but what does the website's (client) private verification key sign?
|
I was reading the SPHINCS+ paper and got confused in the signing with FORS (forest of random subsets) part.
I understand how we can sign a message using FORS but I couldn't understand how we choose the corresponding WOTS+ key to sign the FORS root node with.
If we are going to choose only one of the XMSS trees in the b... |
Compute $n = pq$ where p and q are prime. Fix $e$ to be coprime to $\phi(n)$. Compute $d = e^{-1} \pmod n$ and verify $ed \equiv \phi(n) \pmod n$. We sign the (hash of) a message with $s = h^{d}$. A verifier computes $s^e = h \pmod n$. Why can't an attacker fix $h'$ and solve ${s'}^e = h' \pmod n$ to forge a signature ... |
I need an encryption scheme where a single source/location can encrypt using their private key and while anyone with access to the corresponding public key can decrypt it. It has to be asymmetric to avoid any one else deriving that private key and pretending to become that source. For example, government issues an encr... |
I am currently trying to follow the proof of correctness in the CRYSTALS-Kyber paper. The following is an excerpt of the proof:
On the one hand, I am interested in how exactly one justifies/argues that $\mathbf{y}$ is pseudorandom, based on the MLWE assumption. About the difference $(\mathbf{y} - \text{Decompress}_q(... |
Suppose I have some plaintext $M$, and I want to have some process $f$ to make ciphertext $M':=f(M,s)$, where $s$ is some secret. The ciphertext $M'$ can be decrypted by using some decryption process $M=g(M',k_1,k_2)$, where $k_1$ and $k_2$ are two keys, and $k_1$ is a random key (cannot be controlled, such as the curr... |
I have a course work for university.
The question is:
My solution to the question is:
P||R = D(K,C)
However, in the question it doesn't say we are given R so I'm not sure how to get P from P||R.
This could be because my understanding of concatenation is incorrect as I see it as simply adding the nonce to the plai... |
Is it possible to generate a new valid signature for some arbitrary message using DSA if we know existing signatures for the same message? We are an adversary, therefore we do not hold the private key, but we have access to a couple of signatures for the same message, say $(r_1, s_1)$, $(r_2, s_2)$.
|
I am trying to understand the post quantum based signature scheme Dilithium. I know what the hard problems are in the scheme, but I am having trouble in understanding the utilization of short integer solution in the scheme. Specifically speaking, I can't understand exactly where this problem is used in the scheme. Also... |
Recently, I started looking up for details about implementing a blind signature on ed25519 cryptographic. I saw this article https://stan.bar/blindsig/ by Stanislaw Baranski about it.
In the first point, it says that Bob generates random number (nonce) $k$ in range $(1, q-1)$, computes
$r=k \times G (\mod p)$
$r=k×G(\m... |
I know that the security of both are the same (only nonce size is different). But which one is faster and better to use, when encrypting a lot of files (500+, from 1MB to 200MB)?
|
Given a RSA modulus $n$, which is the product of two safe primes:
\begin{align*}
P &= 2p + 1 \quad\quad\quad
Q = 2q + 1 \\
n &= P \cdot Q = 4p q + 2 p + 2 q + 1
\end{align*}
The hidden group order is then
\begin{align*}
\Phi(n) &= (P-1)(Q-1) = 4p q
\end{align*}
Choosing some random element $z \in \mat... |
In this paper I'm reading (specifically section 3.1), the authors say that the BFV encryption scheme supports plaintext multiplication, which basically means that given a ciphertext, $c$ that is an encryption of a plaintext $p_1$ and a plaintext, $p_2$, one can easily compute an encryption of $p_1 \cdot p_2$. What's mo... |
Considering that P1 has value x, P2 has value y and they want to compute x+y without telling the other what he has,So P1 and P2 secret-share their values to each other.
Now P1 gets x1 and y1, P2 gets x2 and y2 and they locally compute xi+yi. If P1 want to compute x+y = (x1+y1)+(x2+y2), P2 need to send x2+y2 to P1, but ... |
In the SPHINCS+ paper(https://sphincs.org/data/sphincs+-paper.pdf) part 3.2, it explains that they are not using l-trees as a direct consequence of the use of tweakable hash functions.
I have read the tweakable hash function part, but the math made me so confused. Can you explain to me the difference between the usual ... |
Let $(E:y^2=x^3+ax+b) $ on $\mathbb F_q$, with $ q \mod 2=1$.
If $\gcd(3,q-1)=1$ and $a=0$, then it's easy to find the cardinality of the curve $E$ : $|E|=q$.
Are there an another conditions on $(q, a, b)$, where it's easy to find $|E|$?
|
Let $n = pq$, $p,q$ are two large primes, then $\mathbb{Z}_n^*\cong \mathbb{Z}_p^* \times \mathbb{Z}_q^*$. We disclose $n$ and keep $p, q$ secret. Is it secure if we disclose a random element $a$:
$a\in \mathbb{Z}_n^*$, $a = 1 \mod p$
That is, to disclose a random chosen element in $\langle 1\rangle \times \mathbb{Z}_q... |
Web Crypto API allows creating ECC keys with some known curves: https://developer.mozilla.org/en-US/docs/Web/API/EcKeyGenParams
Those are P-256, P-384, P-521.
However as answered at this answer https://crypto.stackexchange.com/a/30273/99862
There are secp256k1, and secp256r1, and maybe more?
Which is the exact P-256 im... |
I am confused about whether/how ZKP based entity/message authentication scheme can achieve identity privacy, especially unlinkability. The security properties I'm looking for in the scheme is authentication (identity proof), such that the prover can prove it has some kind of identity so that it is allowed to be in the ... |
$ G \space is \space an \space elliptic \space curve \space group \space G \space with \space order \space q$
and three hash functions are defined as this:
$$
H_1: \{0,1\}^*\times G \rightarrow Z^*_q
$$
$$
H_2: \{0,1\}^*\times G \times G \rightarrow Z^*_q
$$
$$
H_3: \{0,1\}^*\times Z^*_q \times G \times G \rightarrow ... |
I'm trying to understand the complexity of computing the Merkle root for stateful hash based signature schemes. Section 4.1 of the chapter on hash based signatures in "Post Quantum Cryptography" – by Bernstein, Buchmann and Dahmen (Springer Berlin Heidelberg states) -
($H$ in the following excerpt is the height of the ... |
I am trying to understand how adding padding like the PKCS1.5 RSA signature scheme can prevent the existential forgery attack in RSA. Is it just by changing the structure of the message?
|
In The Algorithmic Foundations of Differential Privacy (Dwork, C; Roth, A), the formal definition of differential privacy is given as:
"
The randomized algorithm $\mathcal{M}$ with domain $\mathbb{N}^{|\mathcal{X}|}$ is $(\epsilon, \delta)-$differentially private if for all $\mathcal{S} \subseteq Range(\mathcal{M})$ an... |
I was reading this post https://senderek.com/SDLH/ about Shamir's hash function, which is defined as follows:
Let $p,q$ be positive prime integers and let $n=p\times q$. Let $\ell = \mathrm{lcm}(p-1, q-1)$. Find $g \in (\mathbb{Z}/n\mathbb{Z})^*$ such that $\ell$ is the smallest positive integer for which $g^\ell \equi... |
What kinds of properties does a KDF need to have in order to be considered secure? What steps should be taken during analysis to test for flaws?
In particular, I mean a KDF that is going to be used as a one-time pad. If the plaintext is 1 MB, then the KDF will produce a 1 MB key. And xor them together tp produce the ci... |
I'm deriving a shared secret using ECDH with Ed25519 keys. According to the specification (page 5), the shared secret then can be any valid Curve25519 public key, i.e. any valid 32 bytes. My environment is such that I need to map this shared secret to being only 31 bytes long. A simple solution to this would be to just... |
In Zero-Knowledge (ZK) proofs/arguments of knowledge, the ZK knowledge property informally says that it is possible to simulate the output of a (malicious) verifier interacting with a prover knowing a witness $w$ without using $w$ at all:
$$\{OUT_{V^*_\lambda} \langle P(w,x) , V^*_\lambda(s_\lambda, x) \rangle\}_{\lamb... |
So I'm currently working on a past exam paper related to cryptography, this question essentially asks the reader why digital signature schemes are not used today.
Yet, when I did my research on this topic online, I found out that most technologies do in fact use digital signature schemes. In fact I'm even confused by w... |
I have a course work for university, the question is:
Consider a symmetric encryption scheme with its encryption operation written as
$$C = E(K, R||P)$$
where $E$ is a block cipher encryption algorithm, $K$ is an encryption key, $R$ is a random nonce (i.e., it is randomly generated for each encryption), $P$ is a plain... |
We call two ensembles $X$ and $Y$ indistinguishable in polynomial time if for every probabilistic polynomial-time algorithm $D$ and for every positive polynomial $p(\cdot)$, and all sufficiently large n's we have $$|Pr[D(X_n,1^n)=1]-Pr[D(Y_n,1^n)=1]| < \frac{1}{p(n)}$$.
One question I didn't confront with at the beginn... |
In the zero-knowledge cryptography nomenclature, we have multiple representations of arbitrary computation suitable for submission to various proof backends (e.g. Groth16). Two specific examples spring to mind: rank-1 constraint systems (R1CS) and Algebraic Intermediate Representations (AIR).
What are these called?
|
If a password p is selected from a space of 2^64 passwords, and the server stores this as a hash, h = SHA-256(p||s) where s is a random 128-bit salt. How many maximum hashes would an attacker need to perform to recover "p" given (h,s)?
I was thinking that this is a pre-image attack so the attacker needs to find the sam... |
I`m solving one crypto problem on rsa.
p^e - q^e = C1 (mod n)
(p-q)^e = C2 (mod n)
n = p*q*r; p,q,r are prime numbers
e = 2 * 65537
We have e, n, C1, C2.
It's impossible to find p, q, r from this system of equations, since there are 3 unknowns in the system of 2 equations. But is there any way to reduce the possibl... |
OU cryptosystem: $N = p^2q$, the secret key is the factorization of $N$, the public key is $g\leftarrow \mathbb{Z}_N$, $g^{p-1} \neq 1\mod p^2$, to encrypt an element $m $ $\in$ $\mathbb{Z}_p$, choose $r\leftarrow \mathbb{Z}_N$, then $Enc(m)= g^m\cdot h^r$, where $h = g^n$
In paper: Paillier's Cryptosystem Revisited [... |
Let $a_n$, and $b_n$ two sequences generated by two LFSR with connection polynomials $P$, and $Q$.
How to show the sequence $(a_n \cdot b_n)$ can be generated by a LFSR wit connection polynomial of degree upper bounded by $\deg(P)\cdot \deg(Q)$?
|
As we know, the Schnorr signature enjoys the linearity property, which does not exist in ECDSA. It seems the Schnorr signature is more efficient and can bring more features than ECDSA. What is the advantage of ECDSA over the Schnorr signature? Will ECDSA gradually be replaced by the Schnorr signature (especially after ... |
If a password is randomly chosen from a space of $2^{64}$ passwords and is stored as an SHA-256-bit hash and a 128-bit salt, how many hashes does an attacker need to perform to recover the password in the worst case?
Would it just be $2^{256}$ hashes because SHA-256 provides $256$ bits of security in a pre-image attack... |
To encrypt plaintext $(P_1, P_2, P_3, ... P_n)$ Ciphertext Feedback Mode (CFB) works as follows :-
$$
C_0 = IV \\
C_i = E_K (C_{i-1}) \oplus P_i
$$
Lets define a modified version of CFB mode as follows :-
$$
C_0 = IV \\
SK_i = KMAC(K, C_{i-1})\\
C_i = E_{SK_i} (C_{i-1}) \oplus P_i
$$
The modified CFB mode encrypts each... |
If an attacker wants to hack the passwords of $2^{10}$ users. And all of these users generate a password from the space of $2^{50}$ passwords** and each password is hashed with PBKDF2 with $2^{10}$ iterations**.
How many hashes would an attacker need to do to get all passwords in the worst case?
I was thinking it would... |
Could you explain the difference between sigma protocol, Schorr protocol with examples. What is the advantage of using commit-and-prove zero knowledge proof over general zero knowledge proof?
|
I have recently understood how we can construct a pseudorandom function from a PRG. However, I would like to prove the reverse - how can I construct a PRG from a PRF?
|
Is there any generic attack on HMAC SHA 256 ?
I am currently reading up on attacks on Hmac sha-256. However most of the papers I've found are about side channel attacks such as Differential power Analysis.
|
How do I calculate the password space of a randomized linked hybrid pasword of 9 images and 10 numbers(0-9)? User allowed to select 4 password
Images=9
Pin= 0-9
Password selection allowed: 4
Every image is linked to a number
Images are randomized at each selection
|
Going through the TPM tutorial: https://google.github.io/tpm-js/#pg_keys
The output of KDF would be some pseudo-random bytes. For RSA, the bytes might not be a prime number. For elliptic curves, the bytes would likely not be a co-ordinate on the curve. Even ignoring that output is coming from a KDF I'm unclear on how ... |
Having a difficult time wrapping my head around the Blom's key distribution. I found an online resource to understand this but still couldn't get it.
I am attaching the screenshot from the book where the author first mentions the algorithm and then he solves an example .
A better explanation to the example how values a... |
I was experimenting with hashcat and aircrack to test WiFi security.
The WiFi AP is a WPA2 encrypted network. The tool I used to capture is bettercap, which captured multiple WPA2 handshakes.
The problem is that from those multiple handshakes I get two valid passwords for the same AP.
Question is, did I find a WPA2 has... |
If I understand correctly (please let me know if any of the following is wrong), a fully homomorphic encryption scheme $\mathcal{E}$ is such that for any messages $x, y$,
$$
\mathcal{E}(x + y) = \mathcal{E}(x) + \mathcal{E}(y) \\
\mathcal{E}(x y) = \mathcal{E}(x) \, \mathcal{E}(y),
$$
i.e $\mathcal{E}$ is a ring homomo... |
In the case of RSASSA-PKCS1-v1_5, is it simply that the cryptographic libraries and APIs are designed to only sign if determined superficially that it has a private key, or is the public key mathematically incapable of signing? Or perhaps in asking this way there is some major wrong assumption I'm making about keypair... |
I have been reading papers about authentication in VANETS and some of them mention a certificate that a trusted authority generates for a vehicle and has the following form:
$${C_{V_i}}=S_{TA}+H(PID_{V_i}|PID_{TA}|P_{TA}|P_{V_I})*x_i$$
Here $S_{TA}$ is a secret that belongs to Trusted Authority.
$H()$ is a hash functio... |
Background:
TEA uses a 128 bit master key $K_{0\ldots3}$. All odd rounds use $K_0$, $K_1$ as the round subkey, and all even rounds use $K_2$, $K_3$. One cycle of TEA applied to the block $A_i$,$B_i$ is: $A_{i+1} \leftarrow A_i + F_i(B_i, K_0, K_1) \hspace{0.5em};\hspace{0.5em} B_{i+1} \leftarrow B_i + F_i(A_i, K_2, K_3... |
I'm trying to implement a naive version of CKKS in Python.
It was great until I start implementing the modulus.
For this kind of schemes, the modulus $q$ is in the range $(-q/2,q/2]$.
How does this work?
In CKKS paper (I think BGV and others do the same) use something like this (a toy example): $c = m (mod$ $q)$. Where... |
In cryptography I am facing the issue to find a generator of some elliptic curve given only the curve over given field and number of elements that the curve has.
The numbers used are enormous so I am struggling to implement any offered scenario how to find generator of an elliptic curve here in stackexchange. If anyone... |
I have two questions I couldn't find straightforward answers to after many searches.
(1) We can perform 2-party MPC over arbitrary functions using Garbled Circuit. To do that, we first need to convert a function to a boolean circuit and then garble it. Is there any tool available where we can convert any arbitrary func... |
This function from Wikipedia calculates the sbox used in AES:
#include <stdint.h>
#define ROTL8(x,shift) ((uint8_t) ((x) << (shift)) | ((x) >> (8 - (shift))))
void initialize_aes_sbox(uint8_t sbox[256]) {
uint8_t p = 1, q = 1;
/* loop invariant: p * q == 1 in the Galois field */
do {
/* multi... |
After implementing and playing around with famous "Chosen Ciphertext Attacks Against Protocols Based on the RSA Encryption Standard PKCS #1" there couple of questions which I can't really grasp.
Why do we get intervals with their ends interchanged?
Why does it work to discard intervals in pairs?
Intervals Ends
I look... |
This is not a duplicate, I'm asking which method is better.
I generate an encoded argon2 hash string, so it'll be stored in database to verify login passwords.
Saved encoded hash has salt of length 16 bytes and tag with length of 32 bytes. I need to derive second different key from the saved key using two parameters:... |
Let $f \in \mathbb{Z}[x]$ be an irreducible polynomial of degree $N$ and $q \in \mathbb{N}$. Consider the rings $R := \mathbb{Z}[x]/f$ and $R_q := R/q$. Obviously, an element of $R_q$ can be represented by means of $\ell(N, q) := N\lceil\log_2(q)\rceil$ bits. In lattice-based cryptography the polynomial $f$ is often cy... |
This question is from Quadratic Sieve Factorization Method. Didn't find the solution on the web also. And not aware of how to solve such questions.
|
so I recently stumbled upon this video by @bertcmiller who created two transactions with the same nonce "k". That seen I researched quite a lot of pages explaining how to recover the private key from this. I know that I first have to find out the "k" value to recover the private key.
The formula for getting k is:
$k = ... |
Given a range of numbers, e.g. [1, 2^256], does each number have the same chances to be picked by a CSPRNG, which are 1 in 2^256?
My concern is that truly random number generators do have this feature, but it's not always secure in cryptography (I presume), because numbers such as 741 in such a large range that is [1, ... |
I'm looking into how authenticated encryption primitives work and was wondering if non-repudiation is provided with these. Investigating further into them led to the answer being that data origin authentication (DAO) are provided by the primitives.
Now DAO is defined as "the source of the information being verified", p... |
The following question is from Stanford cryptography course final exam paper.
Suppose an attacker intercepts a ciphertext $c$ which is the encryption of a message $m\in\{0,1\}^n$ under nonce-based counter mode. Can the attacker create the encryption of $m\operatorname{XOR}1^n$ just given $c$? If so, explain how. If no... |
The algorithm tells that, in the effort of solving $a^x \equiv b \text{ mod }N$:
Choose some $k \in \mathbb{N}$.
Create the baby list: $\{1,a,a^2,...,a^{k-1}\}$
Create the giant list: $\{ba^{-k},ba^{-2k},...,ba^{-rk}\}$ where $rk > N$.
Claim: If two lists have intersection, then this DLP has a solution.
$\textit{P... |
What's the difference between BLS12-381 and BLS12-377?
Previously I thought their basic cryptographic algorithms were same, so it's easy to construct BLS12-381 from BLS12-377, or construct BLS12-377 from BLS12-381, by just changing some curve parameters. Is this correct?
However, in some fields, such as ZK-proof, someo... |
From what I could gather, zero knowledge proof is a way for a prover to convince a verifer of possession of some data without sharing said data. I understood the ali baba cave problem. Diffie Hellman on the other hand seems to be a way for two people to create a shared secret key without explicitly divulging the key it... |
I'm very new to cryptography and am having some issues with the following question
A hash function H encrypts an n-block message m = (m1, m2 ... mn) in CBC mode:
- Block size is 128 bits
- Hash result is the last ciphertext
- IV is arbitrary 1 block long
- Encryption key is arbitrary number -> 128, 192 or 256 bits
- IV... |
What is the flaw of secret sharing? It seems that there is no mention in the literature of the defects of secret sharing, such as the defects of homomorphic encryption may be less efficient computing, what are the defects of secret sharing?
|
After reading "Verify the identity of sender" , which was part of an answer on StackOverflow, I was wondering if the following is possible:
Based on part II, if I am sitting between Alice and Bob:
Can I not wait for Alice to send her public key to Bob.
I block this key and discard it, and send my own public key instea... |
EDIT: The bounty is actually to draw more attention. I accidentally chose the wrong reason.
$E$ – Elliptic Curve over finite field $\mathbb F_p$.
Let $k$ be the embedding degree of the Curve with respect to a prime $q$: The full torsion group of all $q$-torsion points lies in $E(\mathbb F_{p^k})$.
For the MOV attac... |
Regev's Public Key Cryptosystem is defined as follows:
I want to proof the correctness. For this it must be shown that a 0 is decoded correctly and equally that a 1 is decoded correctly. I would present here once my proof:
Case: Encryption of 0
$$b = \sum_{i \in S} b_i = \sum_{i \in S} ( \langle \mathbf{a_i},\mathbf{... |
$$a_1*s+m_1+e_1 = b_1\\\cdots\\ a_n*s+m_n+e_n = b_n$$
The LWE problem is related to finding the solution $s$ to this system, when the $e$ are sampled from the normal distribution. Why the normal distribution?
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For university I am doing a piece of coursework right now. This question is focusing on CPA and collisions using CPA.
Question:
I have attempted to answer part 3, but am not very confident in the answer. If anyone could please take the time to look at the question and look at my answer to let me know if I am going in ... |
Linked is a website that has a capture the flag problem with RSA: https://konsolas-2022-04-24.herokuapp.com/
I know very little about RSA decrypting but I do want to try and solve it, but I'm not sure where to start. I found https://www.tausquared.net/src/pages/ctf/rsa.html which would be useful if I knew the public ex... |
As AES could be considered as a function AES(key, data) that return encrypted data, is there a use of the construct of AES(key1, AES(key0, data)) as the resulting data could be decrypted by key2? Is there a way to determine key2, if key0 and key1 are known?
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I'm trying to perform ECDSA verification in hardware. I'm using the SECT233R1 curve (NIST B-233). I have a question about the hash function used while doing so.
I want to use the SHA256 hash function while signing and verifying. In this case, the hash function will have a larger message length (256-bits) than the ellip... |
I have a course work for university, and am not sure on my answer so if anyone could please take the time out to read the question and my answer to let me know if I'm going in the right direction that would be greatly appreciated.
Question:
My answer:
For a block size of 1 there are no collisions possible using the ha... |
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