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5h
comment El Gamal Decryption with Big Numbers
@DaTechnoGuru Use a programming language and a library for large numbers. For example, BigInteger in java. Python supports large integers out of the box.
19h
comment El Gamal Decryption with Big Numbers
Can you explain where you are stuck? There are descriptions of the math needed to do the decryption all over the internet.
21h
comment Paillier cryptosystem preserve ordering of sums for two integer sequences
Okay, I figured you had the public key and the randomness mixed up.
1d
comment Paillier cryptosystem preserve ordering of sums for two integer sequences
To do the homomorphic operation, all encryption must be with the same public key.
2d
comment If you hashed a hash an infinite number of times would you end up with a unique hash?
No, because you would never stop hashing, so you would never end up with anything.
Apr
24
comment How to securely map an element from an smaller domain to the other element in a large domain
If the technique is public, what stops the adversary from running it herself?Typically the answer to that is a secret key, but you don't want to use secret keys. So, maybe there is no solution?
Apr
24
revised How to securely map an element from an smaller domain to the other element in a large domain
edited title
Apr
24
revised Prime factorization
added 25 characters in body
Apr
24
comment Prime factorization
Sounds like we have at least a few good answers here in the comments. Anyone care to write theirs up?
Apr
23
revised Common Modulus Attack in RSA
added 4 characters in body
Apr
23
answered Common Modulus Attack in RSA
Apr
23
revised Common Modulus Attack in RSA
added 2 characters in body
Apr
23
comment Why does second pre-image resistance imply pre-image resistance
I don't really agree with this answer, because to me, the identity function is not a hash function. Look at the definitions of hash function and cryptographic hash function on Wikipedia. I see problems with the identity function with relation to both of those definitions.
Apr
23
comment Why does second pre-image resistance imply pre-image resistance
I don't think what @scampos has done necessarily deserves a deletion. See this question on meta.SE. We have also discussed this sort of thing on our Meta. At the very least, the answer expands slightly (add some mathematical notation, etc) to Ricky's comment.
Apr
23
comment Is the reverse of the “discrete logarithm problem” equally dificult?
I linked to a question dealing with composite modulus, here is one dealing with prime modulus.
Apr
23
comment Is the reverse of the “discrete logarithm problem” equally dificult?
The op had a comment (now deleted) suggesting modulo a prime.
Apr
23
comment Is the reverse of the “discrete logarithm problem” equally dificult?
For $k=2$ you use Tonelli-Shanks.
Apr
23
revised Is the reverse of the “discrete logarithm problem” equally dificult?
added 16 characters in body
Apr
23
comment Is the reverse of the “discrete logarithm problem” equally dificult?
Typically dlog is defined in a group mod p, but it doesn't have to be. I think that other question contains your answer, though not explicitly, so I'd leave this one open. It says "Yes, the problem of finding... is believed hard unless the factorization of $N$ can be determined". Well, you know the factorization of $p$, it is $p$ :)
Apr
23
comment Is the reverse of the “discrete logarithm problem” equally dificult?
Here is a related question that deals with computing roots when the modulus is composite.