Cryptography Weekly Newsletter - Tuesday, April 28, 2015

Cryptography newsletter

Top new questions this week: If you hashed a hash an infinite number of times would you end up with a unique hash? If you took a hashing algorithm for example MD5 and repeatedly passed the output hash back into the algorithm an arbitrarily large number of times would you eventually end up with one unique hash? My ... hash entropy   asked by Alex Lewis 9 votes answered by Thomas Pornin 27 votes Can cycle finding techniques reduce the memory usage of the MitM attack against 2DES and 3DES? A 2DES like cipher $c=E^{(2)}_{K_2}(E^{(1)}_{K_1}(p))$ where both halves have an $n$ bit key is vulnerable to a meet-in-the-middle attack. Meet-in-the-middle using a big table Create a table ... meet-in-the-middle-attack   asked by CodesInChaos 6 votes answered by fgrieu 1 vote Adding two public keys secp256k1 (the signature scheme used by Bitcoin) has the interesting property that you can add two public keys to get a combined key that requires both private keys to produce signatures for. Is ... ecdsa   asked by Nick ODell 5 votes answered by D.W. 5 votes Has human-generated entropy ever been a real problem? I know the topic of human brains generating random numbers has been discussed here and in Cognitive Sciences before, but I am interested in a particular part of it: In an introductory book to ... entropy   asked by user2891462 4 votes answered by gowenfawr 8 votes Prime factorization What is the largest integer that can be factored by modern algorithm like Msieve and GGNFS in a time less than 5 hours with normal computers? For example, can an integer like ... factorization   asked by Lisbeth 4 votes Can Grover's algorithm be parallized? Using a quantum computer, Grover's algorithm can search an unordered list of length $N$ in time $\sqrt{N}$. Applied to cryptography this means that it can recover $n$ bit keys and find preimages for ... post-quantum-cryptography   asked by CodesInChaos 4 votes Non adjacent form of an integer is unique I have tried to look up the proof for NAF (Non-adjacent form) being unique for every integer, but as far as I have seen, textbooks only mention it as a property of NAF, but no proof is given. Also I ... elliptic-curves number-theory   asked by Vi Jay 3 votes answered by fgrieu 5 votes Greatest hits from previous weeks: Is a die implemented in a physics engine truly random? So, a fair die throw is really random, not pseudo. So, would a RNG implemented as the result of a die throw in a physics engine (say, Newton, Havok, Nvidia's PhysX) be regarded as both ... random-number-generator randomness pseudo-random-generator csprng   asked by Pato Sáinz 8 votes answered by Nova 14 votes 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 18 votes answered by mikeazo 18 votes Can you answer these? Is this variant of SRP useful? I'm interested in using a modified form of SRP as a peer-to-peer authentication method. Since neither side is acting as a host, one of the primary design goals for SRP (that the client doesn't need ... authentication key-exchange srp   asked by Steve Peltz 1 vote How to securely map an element from an smaller domain to the other element in a large domain Problem: I have a small sized domain, say s-bit. It's clear that the probability for an adversary to guess an element is $ \frac{1}{2^s}$. I need to make the probability negligible. However, I need to ... public-key provable-security encoding   asked by user13676 1 vote Double-and-add/Montgomery VS blinding I'm having a hard time understanding why people use constant-time techniques to counter time-attacks, when blinding seems as good and cheaper to implement. Why do people avoid blinding in ECC? elliptic-curves montgomery blinding time-attack   asked by David 天宇 Wong 1 vote

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