Cryptography Stack Exchange Newsletter – Thursday, December 8, 2022

Top new questions this week:

Why does GMP only run Miller-Rabin test twice when generating a prime?

In mpz_nextprime(), after some sieving with small primes, an MR test function is called, with the number of trials set to 25 (github.com/alisw/GMP/blob/…

prime-numbers

asked by fjarri Score of 11 answered by Daniel S Score of 13

How can Garbled Circuits be utilized to reduce the round complexity of GMW?

I’ve been reading this set of notes on some topics in MPC and am having difficulty understanding the transformation the authors make in order to reduce the round complexity of the GMW protocol through …

multiparty-computation garbled-circuits function-evaluation

asked by Lt. Commander. Data Score of 4 answered by Geoffroy Couteau Score of 1

What does break with “usual” classical security reductions in quantum setting?

OK, so I know that this is somewhat really basic in “post-quantum discourse”, but unfortunately I did not find any textbooks/entry level papers specific to the topic of reductions in the …

post-quantum-cryptography reduction rewinding

asked by Kirill Tsar. Score of 3

AES First/Last Round Key Whitening

I’ve found this question from 2014 on Key Whitening: How exactly does key whitening manage to increase security? where is said that AES applies key whitening internally by adding a sub-key prior to …

aes keys

asked by LianoQ Score of 3

Question about Theorem 2 in CRYSTALS-Kyber Paper

I have some questions about the Kyber paper, especially about Theorem 2 on page 6, which I would like to ask here. First of all I quote the following theorem from the paper and ask my questions …

lattice-crypto

asked by P_Gate Score of 3 answered by Mark Score of 2

Why not substitute division of a public value by multiplication to its reciprocal?

MPC protocols have a harder time handling division (truncation) than multiplication. The case I am considering is when the divisor is a public value. Dividing it may lead to a wrong result due to …

multiparty-computation

asked by Zhengyi Li Score of 2 answered by fgrieu Score of 0

Does encrypting data all at once or in chunks using the AES algorithm makes any difference?

Sorry if this is a duplicate but, to be honest, I don’t even know how to search for an answer to it. I’m working in an environment in which I cannot use streams to encrypt data (React Native using the …

aes

asked by Titus Score of 2 answered by Maarten Bodewes Score of 2

Greatest hits from previous weeks:

Difference between stream cipher and block cipher

I read that A typical stream cipher encrypts plaintext one byte at a time, although a stream cipher may be designed to operate on one bit at a time or on units larger than a byte at a time. (…

encryption block-cipher algorithm-design stream-cipher

asked by Ravindra Bagale Score of 58 answered by Paŭlo Ebermann Score of 44

Second pre-image resistance vs Collision resistance

From Wikipedia: Second pre-image resistance Given an input $m_1$ it should be difficult to find another input $m_2$ such that $m_1$ ≠ $m_2$ and $\operatorname{hash}(m_1) = \operatorname{hash}…

hash collision-resistance 2nd-preimage-resistance

asked by ritch Score of 46 answered by yyyyyyy Score of 71

How to attack a “many-time pad” based on what happens when an ASCII space is XORed with a letter?

I’ve already sent my correct solution to a homework exercise from Dan Boneh’s Introduction to Cryptography class on Coursera: “Let us see what goes wrong when a stream cipher key is used more …

stream-cipher one-time-pad xor key-reuse ciphertext-only-attack

asked by sunrise Score of 21

Should I use ECB or CBC encryption mode for my block cipher?

Can someone tell me which mode out of ECB and CBC is better, and how to decide which mode to use? Are there any other modes which are better?

encryption block-cipher modes-of-operation cbc ecb

asked by midhunhk Score of 82 answered by Thomas Pornin Score of 22

What is the importance of Modular arithmetic in cryptography?

Why do we use modular arithmetic so often in Cryptography?

encryption public-key symmetric

asked by user5507 Score of 16 answered by mikeazo Score of 11

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 19 answered by fgrieu Score of 17

What is the difference between a digest and a hash function?

I was wondering about the difference between these two terms… What is the difference between a digest and a hash function?

hash terminology

asked by sekmo Score of 80 answered by Awn Score of 96

Can you answer these questions?

Construct a OWF using two functions $f : X \rightarrow Y$ and $g: X \rightarrow Y$

Given two functions f,g we have to construct h; such that h is one way function. Either f or g is a one way function. We don’t know which one is a one way function. Both f and g are defined over X->…

one-way-function

asked by anon1234 Score of 1

Public key fingerprint verification for large groups

If you were designing: An open source client that offered E2E encryption for e.g. folder sharing between users Each user had public keys for signing (and separate public keys for encryption of …

public-key protocol-design protocol-analysis verifiability

asked by gecad41980 Score of 1

If rabin signature uses a hash function then why cant we use that hash function to sign a message?

About Rabin Signature link According to this paper, the person who wants to sign a message M first appends a random byte string U. => M_new = MU Then uses a compression function to get c = …

hash signature hash-signature rabin-cryptosystem

asked by void_117 Score of 2