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Dec
13
comment How do I find a random BigInteger smaller than another random BigInteger?
@GuutBoy: indeed, selecting a large random value is quite normal. However, he specifically mentioned $Z^*_p$, and not all values in that group are the same. Depending on why he is generating that value, that may be an indication that selecting an arbitrary value may select a value that is weak
Dec
13
comment N way collision of hashes
Is this a Merkle-Daamgard hash, or a generic hash? For MD hashes (at least, the ones without output truncation), there are known ways to compute multiway collisions faster than expected.
Dec
12
comment How do I find a random BigInteger smaller than another random BigInteger?
Why are you selecting a random element within $Z^*_p$? In crypto, the order of the element is usually critical (depending on the intended use); by selecting a random element, you won't know if the order is prime (or, for that matter, nonsmooth).
Dec
12
reviewed Looks OK Why do we have fixed output length in the algorithm SHA1
Dec
12
comment Why do we have fixed output length in the algorithm SHA1
@Ching: no, this is not that question. That question asked "do the SHA functions generate a fixed length output". This question is "why?"
Dec
12
comment What are the potential (major) flaws in this security scheme?
@GuutBoy: this is quite true; however depending on the security model, Alice might not care. One real world example of this situation is Amazon; they don't care who is placing an order (the person placing the order does care that they're giving their credit card to Amazon; TLS does have the checks to make sure authentication happens in that direction).
Dec
11
comment S-Boxes and SP-Network
Hints: they are using the bit patterns as some representation of $GF(2^n)$, and doing the computations there; and yyyyyy is correct, they actually mean $2^k$. So, how nonlinear is the function $x^{2^k}$ computed within $GF(2^n)$? Is a linear function a suitable sbox?
Dec
11
reviewed No Action Needed Why does the recommended key size between symmetric and assymetric encryption differ greatly?
Dec
11
reviewed Close cipher inside and image
Dec
11
reviewed No Action Needed Reduced message expansion in NTRU
Dec
11
reviewed No Action Needed CBC-R when IV unknown
Dec
11
revised Are post-quantum cryptographic ciphers *also* secure if the P=NP conjecture holds true?
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Dec
11
reviewed Leave Closed Application of Cryptography in Auditing
Dec
11
reviewed No Action Needed RSA or Paillier is good?
Dec
11
reviewed No Action Needed Group description in pairing based cryptography
Dec
11
reviewed No Action Needed How to convert a bit string into a point in an elliptic curve? And when to say that a hash function is a random oracle?
Dec
11
answered What are the potential (major) flaws in this security scheme?
Dec
11
comment Is xgcd faster than Fermat for calculating $d$ in RSA?
Typically, when creating an RSA private/public key pair, almost all the time is taken searching for primes; the tiny amount of time taken computing $d$ (or $dp$ and $dq$) is negligible; either method you cite would work.
Dec
10
reviewed Reviewed Probability of factoring keys as a function of bit length
Dec
10
revised Probability of factoring keys as a function of bit length
added 42 characters in body