In public key cryptography we can also use session keys which are symmetric. How do the sender (say a server) provides this session key information to its clients? If the sender (here server) provides the session key by encrypting using its private key, all the clients (including a malicious one...

In a Feistel cipher (as shown below), it seems that the security of the cipher would be entirely dependent upon the function $F$. What requirements on $F$ are necessary for a secure Feistel cipher? Is there any relationship between the function $F$ and the number of rounds necessary to have a sec...

I've got an application (detailed below) that calls for the use of a cipher that is commutative. I've been doing some googling & reading, and there are two algorithms that seem to get mentioned in these discussions--SRA (not RSA) and Pohlig-Hellman exponentiation. (Supposedly SRA is a varia...