Unanswered Questions

24
votes
0answers
771 views

How is the MD2 hash function S-table constructed from Pi?

For fun, I'm learning more about cryptography and hashing. I'm implementing the MD2 hash function following RFC 1319 (http://tools.ietf.org/html/rfc1319). I'll preface by saying I know there are ...
10
votes
0answers
261 views

Shared secret: Generating Random Permutation

-- or: How to Play Poker Without a Dealer I know this question is long but it's a really interesting theoretical problem about shared secrets and multi-party computation. General Problem: "Shared ...
9
votes
0answers
101 views

Choice of multiplication polynomial in Rijndael s-box affine mapping

The Rijndael specification details the design choices for the s-box in section 7.2. They describe the choice of affine mapping as follows: We have chosen an affine mapping that has a very simple ...
9
votes
0answers
280 views

Who first published the interest of more than two prime factors in RSA?

Multi-prime RSA is now a well known technique: it uses $k>2$ distinct secret prime factors in the public RSA modulus, with the advantage that, using the CRT, we can gain a speed boost in ...
8
votes
0answers
132 views

Hardness of finding mutual discrete logarithms of small generators in $\mathbb{Z}_p$

Suppose you want to select a prime $p$ such that finding e.g. $log_2(3)$ in $\mathbb{Z}_p$ is expected to be either at least as hard as the general Discrete Logarithm Problem in $\mathbb{Z}_p$, or at ...
7
votes
0answers
76 views

Has the distributed project “Number Fields @ Home” project benefited cryptography in any meaningful way?

Is there any new understanding, property, or knowledge that has come from the Number Fields @Home distributed computing project? Has any outcome advanced the study of cryptography, or altered ...
6
votes
0answers
209 views

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 ...
6
votes
0answers
501 views

Bleichenbacher 1998 “Million message attack” on RSA

I have been reading Bleichenbacher's 1998 paper on a forged message attack on RSA. The paper assumes access to an Oracle that takes a ciphertext $c$ and will check the decrypted text for valid PKCS #1 ...
6
votes
0answers
518 views

Blowfish in CBC mode with multi-use keys. Is the 64-bit blocksize a fatal issue if one were to encrypt TBs of data?

Crashplan uses 448-bit Blowfish to encrypt the data you send them. The mode used is CBC, keys are multiple use, and IVs are generated with SecureRandom from JCE. Keys are not derived from the ...
6
votes
0answers
138 views

Efficient decoding of irreducible binary Goppa codes and the role of matrix P in McEliece cryptosystem

If we assume that the support for an irreducible binary Goppa code $\gamma_1, ..., \gamma_n$ is publicly known, when is it possible to efficiently decode the code? I know it's possible if one knows ...
6
votes
2answers
182 views

Encrypting or HMACing password digests

Assuming I'm using bcrypt to digest passwords, is any additional security gained by either encrypting or HMACing the resulting digests? By requiring a key to compare password hashes, I would expect ...
5
votes
3answers
312 views

Leak-proof protocol: is such a thing possible?

Is it possible to design a protocol that by itself guarantees that a malicious implementation cannot leak secret data without breaking the protocol? Setting: Alice and Bob have a pre-shared secret ...
5
votes
0answers
626 views

Elliptic curve cryptography related key attacks

This question is an extension of Families of public/private keys in elliptic curve cryptography As described above, bitcoin "type 2" deterministic wallets use a root private/public key pair, where ...
4
votes
0answers
59 views

understanding the proof of knowledge

Recently I've been reading the paper “A New Family of Implicitly Authenticated Diffie-Hellman Protocols”. It's very hard for me to go further. Especially when it comes to the proof of knowledge. ...
4
votes
0answers
103 views

Can a commutative block cipher be indistinguishable from a random one, assuming a random permutation of keyspace?

Define a commutative block cipher with keyspace the finite set $K$, and message space the finite set $S$, to be an application $$\begin{align} E:K\times S&\mapsto S\\ (k,x)&\mapsto ...

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