Cryptography Weekly Newsletter

Cryptography newsletter

Top new questions this week:

Are AES-256's related-key weaknesses exploitable if it is used to build a hash?

Assume it is made a hash based on AES-256 encryption (perhaps because this is hardware-accelerated, but no standard hash is); and it is used the Merkle–Damgård structure, that is padding of the …

hash aes cryptanalysis  
asked by fgrieu 11 votes
answered by Dmitry Khovratovich 12 votes

Why does this square root algorithm work?

I've been doing some elliptic curve cryptography, and a library I'm using has this slightly bizarre algorithm for computing modular square roots: Let $x$ be some quadratic residue modulo $p$ for some …

modular-arithmetic  
asked by ymbirtt 6 votes
answered by Joe Bebel 4 votes

Block cipher and parity of permutation

Can anyone explain the following text passage to me? Most real-world block ciphers build even permutations, because it's hard to build odd ones using small operations (32 bit) on larger (128 …

block-cipher permutation  
asked by RomeoAndJuliet 5 votes
answered by poncho 6 votes

Why are collision attacks important when talking about MAC schemes?

I'm reading Ferguson, Schneier, and Kouno's Cryptography Engineering, and it has a section on MACs. It discusses different types of MACs, but it seems to claim that to acheive 128-bit level security, …

mac collision-resistance  
asked by user54609 4 votes
answered by fgrieu 5 votes

Is there an algorithm to check if an elliptic curve is secure?

As I understand it elliptic curves are of the form $y^2 = x^3 + ax + b$ Where $a$ and $b$ are the curve parameters. However not all parameters will give a curve suitable for crypto purposes. Is there …

elliptic-curves  
asked by user1028028 4 votes
answered by Thomas Pornin 2 votes

Has there ever been more then a theortetical difference between preimage resistance and second preimage resistance?

In other words, has there ever been a point in time in which having the content of a message has actually helped break a hash function?

preimage-resistance 2nd-preimage-resistance  
asked by user3201068 3 votes
answered by poncho 4 votes

Are there any elliptic curve asymmetric encryption algorithms?

RSA offers the functionality of encrypting (short messages, or symmetric keys) with a public key, and decrypting with a private key. However, RSA key generation is extremely expensive, especially for …

public-key elliptic-curves  
asked by hunter 3 votes
answered by DrLecter 2 votes

Greatest hits from previous weeks:

Are there two known strings which have the same MD5 hash value?

Is there an example of two known strings which have the same MD5 hash value (representing a so-called "MD5 collision")?

hash cryptanalysis collision-resistance md5  
asked by Adban 12 votes
answered by M Platvoet 9 votes

Avalanche effect in DES

I couldn't understand the avalanche effect in DES. Could someone explain how avalanche effect happens in DES

encryption block-cipher des feistel-network  
asked by user5507 5 votes
answered by woliveirajr 11 votes

Can you answer these?

Security of RSA for paranoids with padding?

RSA for Paranoids (RSAP) (in cryptobytes v3n1), also known as Unbalanced RSA, is a variant of RSA proposed in 1995 by Adi Shamir, as a mean to increase the RSA public modulus size while keeping …

rsa public-key rsap  
asked by fgrieu 3 votes

A known-plaintext attack on an LFSR-based stream cipher

I am reading a book about Cryptography, and I am stuck in a question. I am really trying to solve it for weeks. But I think the problem is I couldn't understand the whole picture. The question was …

known-plaintext-attack homework lfsr  
asked by Tim Tuckle 1 vote

Is this a correct understanding of Universal Hash Functions?

I'm studying universal hash functions and have been reading several papers but now i'm focusing on Wegman and Carters original paper from 1979 (Universal classes of hash functions) and the H1 class. …

hash universal-hash  
asked by user12949 1 vote
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