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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?
added 23 characters in body
Feb
19
revised What is the polynomial to use in the Massey-Omura cryptosystem?
added 58 characters in body
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.
Feb
18
reviewed No Action Needed Key Length vs KeySpace
Feb
18
reviewed Close AES encryption takes more time to decrypt than encrypt
Feb
18
comment AES encryption takes more time to decrypt than encrypt
I'm voting to close this question as off-topic because it's really a question about a specific AES implementation, not AES in general
Feb
18
reviewed No Action Needed Using hashed password as shared secrets. Good or bad idea?
Feb
18
reviewed No Action Needed How to show that a function is not a PRP?
Feb
18
reviewed Close Given infinite unencrypted and encrypted texts, can I find the algorithm?
Feb
17
comment Crack RSA with additional information
I would suggest you get better textbooks, then (:-). Or, rather, if the textbooks say "one way to generate $d$ is with $d = e^{-1} \bmod \phi(N)$", well, that's as correct as far as it goes; however that's not a necessary condition.
Feb
17
comment Crack RSA with additional information
Actually, it's not necessary true that either of $e_Ad_A-1$ or $e_Bd_B-1$ are multiples of $\phi(N)$; all we know is that they will be multiples of $\lambda(N) = lcm(p-1,q-1)$. This subtlety will prevent straight-forward approaches such as you have outlined from working. On the other hand, the answer you pointed to will work.
Feb
17
answered ECIES with AES-GCM
Feb
17
comment Pseudorandom number generators based on hard problems in mathematics
@Melab: can you please point me to the security proofs for RSA or Diffie-Hellman? That is, the ones that don't start off assuming that the "RSA problem" or the "Diffie-Hellman problem" is hard?
Feb
17
reviewed Approve What prime lengths are used for RSA?
Feb
17
comment Affine transformation in finite field SubBytes
possible duplicate of How are the AES S-Boxes calculated?