Cryptography Stack Exchange Community Digest

Top new questions this week:

On what Galois field AES really works?

I'm trying to understand the GF theory, but every time I come across information about AES it all makes no sense. In my opinion $GF(2^8)$ defines any polynomial of the form: $a_{7} x^7 + a_{6} x^6 + ...

aes finite-field  
asked by Tom Score of 8
answered by fgrieu Score of 11

Is there any threshold-crypto library that is production-ready?

I am wondering if there is any available threshold crypto library that is well-audited and ready to be used in production. Any pointer is appreciated.

threshold-cryptography  
asked by threshold_crypto_library Score of 3
answered by Kostas Chalkias Score of 2

What is the difference between AES-CCM8 mode and AES-CCM mode?

I know AES-GCM and AES-CCM but what is the difference between AES-CCM8 mode and AES-CCM mode ? Is it the length of the cipher?

encryption aes block-cipher ccm  
asked by dawklrw Score of 2
answered by Daniel S Score of 1

Security of equal discrete logs (over different bases)

I am trying to find a reduction for the following DLOG problem in generic groups. It is a simple generalization but I'm not finding any reference (the closest being the Chaum-Pedersen signature scheme ...

discrete-logarithm reference-request  
asked by crypcrypcryp Score of 2
answered by Daniel S Score of 4

Validating AES GCM authentication tag between two different implementations

I'm a bit confused on how to validate the authentication tag between two different AES GCM implementations. One implementation (on my part) is in Java. The other, I don't know. In my implementation, ...

aes authenticated-encryption openssl gcm aes-gcm  
asked by newiatester Score of 2
answered by Maarten Bodewes Score of 2

NIST vs ISO Encryption standardisation process

skinny cipher has been lately considered as ISO/IEC standard while is still competing as building block of Romulus AEAD in NIST LWC finalists. what is the difference between the two ISO and NIST ...

nist standards lightweight iso  
asked by hardyrama Score of 2
answered by DannyNiu Score of 4

Carry-less multiplication vs. multiplication in $GF(2^k)$

I implemented carry-less multiplciation using the CLMUL instruction set. This is similarly fast to simple modulo multiplication. But computating the result mod some polynomial is still very slow. I do ...

finite-field  
asked by Tom Score of 2
answered by Daniel S Score of 2

Greatest hits from previous weeks:

What is safer: ZipCrypto or AES-256?

Like in title: which one of these encryption methods (ZipCrypto, AES-256) is more secure and why? I am asking about it because I'd like to know which should be preferred when compressing files with ...

aes file-encryption compression  
asked by alex Score of 75
answered by mikeazo Score of 62

How does one attack a two-time pad (i.e. one time pad with key reuse)?

My question might appear the same as the question Taking advantage of one-time pad key reuse?, but actually I did read all the answers and none of them helped me with the details I need. I am new to ...

cryptanalysis one-time-pad key-reuse  
asked by Samer Makary Score of 74
answered by poncho Score of 79

How can I understand whether my C implementation is constant-time or not (i.e. resistant to timing attacks)

I have a code for polynomial multiplication and it is written in C. I heard that whether a particular instruction is "constant time" can vary by architecture and by processor model and there ...

timing-attack  
asked by esra Score of 20
answered by Peter Green Score of 30

Does the SHA hash function always generate a fixed length hash?

I'm using the SHA1/2 family of algorithms for a particular project. I was wondering if all the SHA algorithms return a fixed length hash regardless of the length of the data.

sha-1 sha-2  
asked by Robin Rodricks Score of 18
answered by fgrieu Score of 17

How much would it cost in U.S. dollars to brute-force a 256-bit key in a year?

I am often told that any key can be broken and that it is only a matter of time and resources for any key to be broken. I know that this is technically true. However, I think that there is probably a ...

brute-force-attack  
asked by John Fischer Score of 219
answered by mikeazo Score of 193

Where and how to store private keys in web applications for private messaging with web browsers

I am working on a web application enabling users to communicate over private messages which is just one part of the whole system. The main focus during my development process is to protect the privacy ...

public-key secure-storage keys  
asked by John Doe Score of 38
answered by mti2935 Score of 32

How do I calculate the private key in RSA?

Given $n=pq$ for $p,q$ known, I can calculate $\phi(n)$. $e$ is selected such that $\gcd (e,\phi(n)) = 1$. Using this, how do I calculate the RSA private key? Example: I have $n = 35$, with $(p,...

rsa  
asked by Ali Gajani Score of 4
answered by curious Score of 2

Can you answer these questions?

What are the key difference between Shannon entropy and Guessing Entropy?

Any body can explain, what are the key difference between Shannon entropy and Guessing Entropy? In some research I got entropy uses binary search or balanced huffman tree. Guesswork uses linier and ...

entropy  
asked by Barua Himel Score of 1
answered by kodlu Score of 0

Observations about ENT's Chi Squared test on my own RNG—and HotBits's score

Basic question: ENT seems to trip up generators that pass NIST 800-22 and maybe even dieharder. How do the latter two test suites miss such an obvious failure? There are two things I want to mention ...

random-number-generator randomness trng  
asked by Adam Score of 2
answered by Paul Uszak Score of 0

Can I prove that from a set of ciphertexts one is encrypting $g^0$ and the others are encrypting $g^b$ where $b$ is a negative value?

Consider for example this set of encrypted values under the Elgamal keys $y_0$,$y_1$,$y_2$: $$ Enc_{y0}(g^0),Enc_{y1}(g^{-20}),Enc_{y2}(g^{-10}) $$ Can I prove that one value is $g^0$ and the others ...

zero-knowledge-proofs elgamal-encryption  
asked by Μενέλαος Κοκάρας Score of 1
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