Tagged Questions
2
votes
1answer
42 views
How is ElGamal not secure under chosen ciphertext attack, but semantically secure in some cases?
I know that you can create a ciphertext c' using c and then find the corresponding m' for c' which you can use to find m for c. So, doesn't this mean that it is not semantically secure? But I also ...
3
votes
1answer
50 views
Chosen ciphertext insecurity in an ElGamal variant
I'm trying to prove something and if I can show that there is a simple way to calculate $(g^a \bmod p)^k$ if I know both $g^k \bmod p$ and $g^a \bmod p$, then (I think) it will help me prove it, but ...
0
votes
0answers
64 views
Use curve25519 for ElGamal crypto
DJB described curve25519 in his paper which can be found here: http://cr.yp.to/ecdh/curve25519-20060209.pdf. It seems that the main purpose was for Diffie-Hellman key exchange. I think this means that ...
5
votes
2answers
203 views
Besides key and ciphertext sizes what are other advantages of elliptic curve versions of various protocols?
There are elliptic curve variants of Diffie-Hellman, ElGamal, DSA and possibly other protocols/algorithms. I know that these elliptic curve variants have smaller key and ciphertext sizes which will ...
2
votes
1answer
318 views
Generalizing the conversion of Diffie-Hellman to El Gamal
How can we generalize the conversion of Diffie-Hellman to El Gamal public-key encryption scheme? The goals is to be eventually able to show that any 2-round key-exchange protocol can be converted into ...
4
votes
2answers
766 views
How to calculate the time it'll take to crack RSA or DH?
Sometimes the easiest way to describe security of a type of cryptography is to say that "the time it takes to solve for an x-bit key would be y years". How would one go about doing such a calculation ...
