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Feb
20
revised Hash “Preimage by product” resistance
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Feb
20
revised Hash “Preimage by product” resistance
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Feb
20
revised Hash “Preimage by product” resistance
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Feb
20
answered Hash “Preimage by product” resistance
Feb
20
comment How to find generator $g$ in a cyclic group?
@LRM: you misunderstood the pronoun (and I fixed the answer to be clearer); compute $h^2$, and if this is not 1, then $h^2$ is your generator (not $h$ -- I used "it's", and it wasn't clear which that referred to). Then, we needn't bother to check if $(h^2)^q = 1$, as that's $h^{2q} = h^{p-1}$, and Fermat's Little Theorem says that'll be 1.
Feb
20
revised How to find generator $g$ in a cyclic group?
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Feb
20
reviewed Approve Find a polynomial time algorithm for the following problem
Feb
20
reviewed No Action Needed LUKS multiple key slots - what's the intuition?
Feb
20
reviewed No Action Needed How does double-encryption work with a client server model
Feb
20
revised Complexity of attacks on affine cipher
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Feb
19
answered Complexity of attacks on affine cipher
Feb
19
comment What is the polynomial to use in the Massey-Omura cryptosystem?
@Melab: What is $(x+1) \times (x+1)$ (doing arithmetic in $GF(2)$)?
Feb
19
comment What is the polynomial to use in the Massey-Omura cryptosystem?
@Melab: A polynomial is prime if it isn't the product of two smaller polynomials; for example, $x^2+x+1$ is prime, while $x^2+1 = (x+1)\times(x+1)$ is not. As for determining a valid representation on the fly for an arbitrary $n$, well, I don't know of a cheap way. Until you learn more, I'd suggest you stick with a fixed value of $n$ (and use a known valid polynomial).
Feb
19
revised What is the polynomial to use in the Massey-Omura cryptosystem?
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Feb
19
revised What is the polynomial to use in the Massey-Omura cryptosystem?
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Feb
19
answered What is the polynomial to use in the Massey-Omura cryptosystem?
Feb
19
comment Encryption - How to find $\sigma$?
Oh, and the question has $+$ with the meaning of "exclusive-or", not modular addition. I know that because if they meant modular addition, the resulting cipher wouldn't be quite so trivial as to be solvable with a single known plaintext/ciphertext pair.
Feb
19
comment Encryption - How to find $\sigma$?
Lets try it this way: if $\sigma$ is linear, then we know that $\sigma(X+Y) = \sigma(X) + \sigma(Y)$. How can we use this to simplify your expanded expression?
Feb
19
comment Encryption - How to find $\sigma$?
You're looking at it the wrong way. Instead, consider linear (and affine) functions; can you show that this encryption method is linear (actually, affine)? If so, how can we simplify it?
Feb
18
comment Encryption - How to find $\sigma$?
I believe that it is assumed that you know $\sigma$; you are asked, given $(L'_0, R'_0)$ and $(L'_4, R'_4)$, how to reconstruct the relationship between plaintext and ciphertext. Actually, the question allows you to pick the $(L'_0, R'_0)$ values; I don't see that's necessary; you can use an arbitrary set of values.