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Sep
23
answered How is a public/private key pair generated from a Diffe-Hellman key exchange?
Sep
23
comment Elliptic curve point addition with $Z_1 = Z_2 = 1$
If you add two points with $Z_1=Z_2=1$, the resulting point will (in general) have $Z_3 \ne 1$. Given that we typically do a full addition chain, and not just add two points together, what is your stategy when it comes time to do the second addition?
Sep
23
comment Extend OTP on random data?
Ill-advised to say the least; it the attacker guesses a crib (that is, a moderately long word within the ciphertext), then that gives him the correct decryption to a significant fraction of the rest of the ciphertext, and it should be fairly easy to distinguish whether this significant rest of the ciphertext is plausible. Hence, it should be straightforward to decrypt the entire message (ciphertext-only attack scenario).
Sep
23
comment Is succinct verification of an arbitrary data transformation theoretically possible? Is it feasible? How?
Yes, doing this with a Turing-complete set would appear to be equivalent to the halting problem.
Sep
23
answered Lower bound of key space size with relaxed perfect secrecy
Sep
22
answered Generating a 30-32-bit PRP
Sep
19
comment Non CPA on custom MAC
Hint: what happens if you compute the MAC of a message that consists of two equal blocks?
Sep
19
comment Are any of the major asymmetric ciphers distinguishable (EG, RSA, ECC)?
@pg1989: no, there is a known efficient procedure to compute it without the factorization; math.fau.edu/richman/jacobi.htm outlines how it can be done.
Sep
19
awarded  Nice Answer
Sep
16
comment Explain same encryption time for two files of different sizes
Are both so fast that your timer can't actually measure it?
Sep
13
awarded  Nice Answer
Sep
11
comment How to propagate error in variable-sized message?
Actually, if performance isn't an issue, FFX works for long messages too.
Sep
11
answered Security of a signature scheme based on both factoring and discrete logarithms
Sep
11
reviewed No Action Needed Basic Encryption and Decryption related question
Sep
11
awarded  hash
Sep
10
comment Is there a system where I can securely store a secret value and compare a semi-ambiguous input to it?
Not an answer, but some feedback on the possible ergonomics of the idea: I've heard of this sort of idea before (on ATMs, to remap the numeric keypad randomly) to discourage shoulder-surfing. However, it turned out that people hated the idea (because they remembered their pin as a series of keystrokes; they had to look for each digit in succession). I suspect they'll have a similar reaction to your idea.
Sep
10
answered Lower defree annihilator of function
Sep
10
comment Lower defree annihilator of function
What does this question have to do with cryptography?
Sep
10
reviewed No Action Needed Definition of authenticity
Sep
10
reviewed No Action Needed 2 round GOST_28147-89 cipher distinguisher