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Aug
12
comment Deterministic Rand function for Winternitz One Time Signatures
I need (at least) 256 bit outputs because the Winternitz OWF has a 256 bit output. I need (at least) a 256 bit key, because the risk of collisions in the leaf keys must nut exceed the risk of collisions in the message digest function. I need a 256 bit seed because the number of leafs is $2^{250}$ and the total number of independent leaf keys is $2^{256}$.
Aug
11
comment SHACAL in SHA-256
Yes, SHACAL-2 was e.g. selected as part of the NESSIE portfolio. However, it should be noted that some standard modes of operation don't have a 256-bit equivalent, such as GCM.
Aug
10
answered SHACAL in SHA-256
Aug
9
comment Discovering private exponent from public key
Correction: The order $q$ of $g$ is the least positive integer such that $1 = g^q \bmod N$. You are correct that an element $g$ is a generator of the multiplicative group if its order is $q = N-1$. Also please note that $N = 251$ isn't a safe prime, since $(N-1)/2 = 125$ isn't a prime.
Aug
9
comment Discovering private exponent from public key
The parameter $n$ in my answer is an arbitrary attack parameter that might be any value between $0$ and $128$.
Aug
9
comment Discovering private exponent from public key
@Joe In SRP, $g$ is supposed to be a generator of the multiplicative group, meaning that the order of $g$ should be $q = N-1$. Since $N$ is supposed to be a safe prime, the only other possible values are $q = (N-1)/2$, $q = 2$ and $q = 1$. Checking the order of $g$ is done by finding the least $q$ such that $g = g^q \bmod N$.
Aug
9
answered Discovering private exponent from public key
Aug
7
revised Interleaving bytes to make an effectively larger block size
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Aug
7
comment Interleaving bytes to make an effectively larger block size
If by "interleaving" you mean transposing, please see the second case in my answer. Your function has approximately the same collision rate as CBC mode or CFB mode under CPA, but at the expense of three AES invocations per 128 bits, instead of just one.
Aug
6
revised Interleaving bytes to make an effectively larger block size
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Aug
5
revised Interleaving bytes to make an effectively larger block size
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Aug
5
revised Interleaving bytes to make an effectively larger block size
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Aug
5
revised Interleaving bytes to make an effectively larger block size
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Aug
5
revised Interleaving bytes to make an effectively larger block size
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Aug
5
answered Interleaving bytes to make an effectively larger block size
Aug
3
comment Cryptographically Secure Hash Algorithm with Very Specific Property
1. What exactly do the operators $\oplus$ and $+$ signify? Bitwise xor and string concatenation, or something else? 2. Are the $K_i$ values supposed to be of a fixed bit length, or do you want the relation to hold for inputs of any length?
Aug
2
revised Correctly generating cryptographically secure pseudorandom numbers (in C)?
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Aug
1
comment Using Lattice-based cryptography for TLS\SSL
@XCore I work mostly with independent software vendors. For them, GPL is as prohibitive as patents.
Aug
1
comment Using Lattice-based cryptography for TLS\SSL
I think you might add the fact that NTRU is patented to the list of reasons. It doesn't have anything to do with cryptography, but it is a very strong reason for a lot of people to bend over backwards searching for alternatives.
Aug
1
comment Deterministic Rand function for Winternitz One Time Signatures
Does there exist a standard Salsa/ChaCha variant that uses a 256 bit nonce (for at least 256 bit outputs) as per the question? Do you mean BLAKE?