Additional Reading material:
Lecture Notes on Cryptography
Handbook of Cryptography
Cryptography FAQ
Merkle's Puzzles.
How SSL Works
RSA
Proof in MSWord
RSA Proof in HTML/IE
Interesting Stuff:
1]
The official DES Standard
document.
2]
Breaking DES - 1
3]
Breaking DES -2.
4]
Good Papers from Rivest
Papers to Read