All Questions

In ElGamal, how does knowing the secret number used for a signature reveal the signer's private key? How do two signatures using the same secret number reveal the signer's private key? [Hint: p-1 is ...

I want to compute an identity function over encrypted vector on a third party. For example, F(x) = [a1,a2,..,an] where x is a tag. However, i do not want the third ...

I have a question from my teacher: "Why can a symmetric encryption algorithm be considered a pseudo-random number generation algorithm? Can anyone explain it to me? And sorry if my english is not ...

I would like to know if this process is feasible under homomorphic encryption, ideally under paillier or any other additive scheme Apply a mask X to obfuscate a message A ie. Am = A (op) X where (op)...

I wrote a toy pseudo-random permutation out of a Feistel network using blake2b. However, looking at the distribution of permutations for small n = 6, it's clearly not uniform unless many rounds are ...

What are some good books to learn basics of crpytography? Maybe with some coding examples? And what are must read cryptography articles? I am a beginner and i have got a few knowledge on crpytography.

The Curve25519 is defined over the prime $2^{255}-19$ with $A = 486662$, so that the curve equation is: $y^2 = x^3 + 486662x^2 + x$ I'm trying to understand, why the parameters are what they are. ...

My professor has given me an RSA factoring problem as an assignment. The given modulus is 30 decimal digits long. I have been searching a lot about factoring algorithms. But it has been quite a ...

In the context of zk-SNARKS, we are given an arithmetic circuit $C$, public outputs $y_1, \ldots, y_n = \mathbf{y}$ and some public inputs $x_1, \ldots, x_ℓ$. The prover wants to prove knowledge of ...

I'm having some issues finding keys to a Feistel network. The function is unknown but we can have as many plaintexts and their given ciphertexts as we want. I'm trying to generalize the cryptanalysis ...

I recently implemented a very simple SHA256 hashing program in C++, since the SHA256 hash function's block size is 512 bits or 64 bytes, and messages less than that size have to be padded as per the ...

Actually, I want to know whether there are explicit and formal definitions of the properties which are authenticity, integrality or non-repudiation. It seems that the signatures and MACs can achieve ...

From an answer to the question RSA maximum bytes to encrypt, comparison to AES in terms of security? I learned that there is a theoretical limit of how much data can be safely encrypted with symmetric ...

I have an example of a CMAC computation, which I want to reproduce in Python, however I am failing. The example looks like this: ...

I am a layperson interested in how cryptography works. I would like to know why you can use shorter keys with elliptic curve Diffie-Hellman (ECDH) than with the discrete log DH key exchange. Both have ...

Below question is a part of my assignment and I was completely clueless about where to start from. So, I am posting it here for the purpose of getting hints/resources to help me get started. $ \ '' $...

I have really googled the entire internet but could not find a clear algorithm for hummingbird-1 cryptography.The problem emerges in the decryption module: What is the initial value of state register ...

I just read this blog post (Signal - Technology Preview for secure value recovery) by Signal and something is not quite clear to me. In section "Stretching beyond a KDF" they generate a ...

$\textbf{13.10 (Probabilistic full domain hash).}$ Consider the following signature scheme $\mathcal{S} = (G,S,V)$ with the message space $\mathcal{M}$, and using a hash function $H: \mathcal{M} \...

Here is what I understand the algorithm to be: Let $G, H$ be one-way functions, where G outputs the 0 string. 𝐸𝑛𝑐𝑜𝑑𝑒 Select a random $𝑘$-bit integer $𝑟$. Pad out $𝑚$ with $0$s to length $𝑙...

hi I can't seem to be able to encrypt WEBM files and get back any valuable information like key value or key id so i can use them with EME API and create a dash media player so i can protect my media ...

I have generated one RSA-2048 signing key and one DSA-2048 signing key, using gpg command gpg --full-generate-keys I would expect the key to have size 2048 bits, ...

I've seen from the SafeCurve criteria that one should try to avoid small complex multiplication field discriminant as it can speedup the discret log computation via the Polard Rho method. However, I ...

I am new to cryptography, I am very interested in cryptography, thank you for your answer.

Consider 3 entities A,B and C. I want A to be able to encrypt a document that can be decrypted only when keys of both B and C are combined. This question talks about a similar problem, but it uses AES....

Consider the Type I lattice trapdoor in [GPV08]: https://eprint.iacr.org/2007/432.pdf Suppose a PPT adversary is given the LWE trapdoor function in the picture: $g_{A^\top} (s,e) = A^\top s + e = b (...

I spent a lot of time looking for an answer to this question, but the majority of answers never explicitly explain why the client's public key is never used; it's always the server's public key that's ...

I'm new to this forum, and I'm certainly not a cryptography expert. I have to decrypt a message and I have NO IDEA what algorithm I can use. In the same context, I solved another encrypted text using ...

As we known, a homomorphic signature scheme consists of the usual algorithms $(\text{KeyGen} , \text{Sign} , \text{Verify})$ as well as an additional algorithm $\text{Evaluate}$ that “translates” ...

Why we can't use simple additions to exchange keys in the diffie-hellman protocol? Example: Alice needs to send a secret "abc". Alice encrypts the key using a secret key "121". Alice sends "bdd" to ...

is there anyway to download videos from cloudfront ? I got a paid subscription but i cant download

thanks for taking a look at my post, i did a search and i couldn't find any information about this topic, so i thought i would post my question here. my question is this, i have recently learned that ...

I'm a newbie in this field and am trying to learn a bit about how to write cryptographic hash functions. To get some hands-on, I tried updating the PySHA2 algorithm for Python 3.6 and up (the original ...

I'm trying to establish E2E secured channel with nearby devices (using WiFi direct). Obviously, I wouldn't like to rely on internet connection. Can I use the signal protocol without a server? 1)Will ...

I'm creating a password management application and I'm considering using the following procedure to keep passwords safe: Asking the user for raw_password, for ...

Given the letter-number cipher: a=00, b=01, c=02, etc., encrypt the word 'hi' and decrypt its ciphertext using RSA. The public key is (5,35) and the private key is (29,35). I know that 'hi' is ...

The question that I am trying to answer is as follows: 10.14. The parameters of DSA are given by p = 59,q = 29,α = 3, and Bob’s private key is d = 23. Show the process of signing (Bob) and ...

I'm a bit confused why it's hard to break Diffie–Hellman Let's take the example ALICE has G, a, and n BOB had G, b and n Eve ...

What should be the objective function , constraints and bounds for the model for Related-key impossible differential search on simeck cipher using mixed integer linear programming (MILP)?

So I was trying to compute a normalized model of elliptic curve as described here. Consider $p$= ...

In feistel cipher , does it matter that number of rounds ? is using more rounds will give the best result? or it's all about the key size ?

i want to get q, but i dont know how. Informations: N = ...

In Serious Cryptography by Jean-Philippe Aumasson on p. 46, paragraph "Provable Security", it says: Provable security is about proving that breaking your crypto scheme is at least as hard as ...

I was able to find the irreducible polynomial used in AES128-GCM: $x^8+x^4+x^3+x+1$. But I cant' find the one for AES256, I'm searching in OpenSSL implementation of AES256 but with no luck so far.

The code is ovTSeyGlJoIrvjLvvoLtM0NMsqbs7INB2zzciLW7Nek= Which is I believe is encoded in Base64. However, decoding it through ASCII results in a garbled message of ¢ôÒ{!¥&+¾2ï¾í3CL²¦ììAÛ<ܵ»...

In light of current events (Zoom getting strong headwinds for using AES-128 in ECB mode), I was wondering what the general approach is to packetized data encryption, where the packet length (UDP for ...

I am using CAPI Engine in OpenSSL and I did some test. When I use TLS 1.0 or 1.1, during handshake and RSA signing, PKCS padding is chosen. When I use TLS 1.2, RSA signing uses PSS padding. What ...

I have designed a s-box and now i want to find out its properties i.e. what are the values of non linearity, SAC, BIC etc?

I'm attempting to validate an Authenticode signature (generated by signtool /fd SHA256 /f <code signing PFX> /p <PFX password> test.exe), and I've run ...

I want to create a NIZK proof of a multi-exponentiation via Groth-Sahai proofs. In the lectures of Jens Groth in a winter school of Bar-Ilan University, he shows a way to transform multi-...