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Mar
17
comment Anonymity problem after voting with blind signatures
"Registrar can in cycle try to do $sm'_i \cdot sm_j^{-1} \pmod N$ to find some $r_k$" -- Can you explain why you expect this to have a higher success probability than generating a random $r$?
Mar
17
revised Anonymity problem after voting with blind signatures
deleted 12 characters in body
Mar
17
comment Anonymity problem after voting with blind signatures
Are you using the same $r$ for different messages?
Mar
17
comment How is McEliece chosen plaintext secure?
I'm certainly no expert on McEliese, but why would one use a random prefix when you could have a strong random permutation instead? That's like reinventing the PKCS#1v1.5 RSA padding.
Mar
15
awarded  Nice Answer
Mar
15
revised Why is Pearson hash not used as a cryptographic hash?
added 545 characters in body
Mar
15
comment Why is Pearson hash not used as a cryptographic hash?
@johnfound Your running the j loop in the hash backwards breaks the attack code. (That does not mean the change is a security improvement)
Mar
15
revised Why is Pearson hash not used as a cryptographic hash?
added 635 characters in body
Mar
15
comment Why is Pearson hash not used as a cryptographic hash?
@poncho Generalized the code to include a first pre-image attack like that.
Mar
15
revised Why is Pearson hash not used as a cryptographic hash?
added 187 characters in body
Mar
15
answered Why is Pearson hash not used as a cryptographic hash?
Mar
15
comment Why is Pearson hash not used as a cryptographic hash?
Such a hash never contains duplicate bytes. That's a distinguisher attack, but it prevented the collision attack I was looking for.
Mar
13
comment Why inversion and multiplication operations are costly in elliptic curves?
On prime fields, an inversion costs over 100 multiplications, so we rarely use more than one inversion (at the end of a scalar multiplication, converting from projective/extended coordinates to affine coordinates). But I think the ratio is much smaller in binary fields, so trade-offs are more interesting there.
Mar
13
comment Why inversion and multiplication operations are costly in elliptic curves?
I'd expect squaring to be counted as a (fraction of) a multiplication. For example, some papers, I read, counted a squaring as 2/3 of a multiplication.
Mar
11
comment Using Counters instead of MAC in CBC mode
CBC decryption propagates an error only to the next block.
Mar
10
comment Fast algorithm for reduction modulo a prime
How big are $a$ and $b$? How big is $|a-b|$? How does the larger algorithm you want to use this in look like?
Mar
9
comment Why haven't we proven many things computationally secure yet?
We haven't even shown that P!=NP.
Mar
8
comment How to calculate min entropy of the output of PRNG?
You don't even need a calculation: It's 0.
Mar
7
revised Decrypting an Affine Cipher with known characters
deleted 9 characters in body; edited tags
Mar
7
revised Affine cipher: calculate the key from a known plaintext/ciphertext pair
edited tags