The following provides some resources for cryptography and information about algorithms used.

Encryption Algorithms (Reversible)

RSA
Public key cipher using varying key sizes (averages are 512, 768, 1024 and 2048 bit)
It is around 100x slower than DES and obtains its strength from the use of large prime numbers
http://world.std.com/~franl/crypto/rsa-guts.html
http://www.orst.edu/dept/honors/makmur/
http://www.google.com/search?q=RSA

DES & Triple DES
DES is a symmetric 64-bit block cipher using 56-bit keys.
DES is breakable within 24 hours on a specially built piece of hardware, and has been shown to be cracked within about 4 months by large numbers of individuals using general purpose computers.
http://www.eff.org/descracker/
http://csrc.nist.gov/cryptval/des.htm
http://www.tropsoft.com/strongenc/des3.htm
http://www.yourgateway.to/triple-des/

RC2 & RC4
Variable length keys
RC2 is a symmetric 64-bit block cipher
RC4 is a stream cipher
Keys can be from 1 to 2048 bits long
Approximately 10 times faster than DES
http://www.smartcomputing.com/editor...F67r04%2Easp#b

Skipjack
Symmetric 64-bit block cipher
Key size is 80 bits
http://www.cs.technion.ac.il/~biham/Reports/SkipJack/
http://www.totse.com/en/privacy/encr.../skipjack.html
http://www.defenselink.mil/news/Jun1..._bt316-98.html

[U]IDEA[/I}
Symmetric 64-bit block cipher
128-bit key
IDEA runs at about half the speed of DES
http://www.cs.nps.navy.mil/curricula...chap04_43.html
http://www.finecrypt.net/idea.html
http://www.fourmilab.ch/speakfree/windows/doc/idea.html

Blowfish
Symmetric 64-bit block cipher
Variable length key
Key size ranges from 32 to 448 bits
Runs at about 4 times the speed of 3DES
http://www.counterpane.com/blowfish.html
http://www.tropsoft.com/strongenc/blowfish.htm (Blowfish)
http://www.tropsoft.com/strongenc/twofish.htm (Twofish)

AES
128 bit block ciphers
Support 128 and 256 bit keys
http://csrc.nist.gov/encryption/aes/
http://www.ciphers.de/products/bppfo_speed.html

Digital Signature Algorithms

RSA
See above

DSA & DSS
public key algorithm used to generate digital signatures
Key sizes between 512 and 1024 bits 9in 64-bit increments)
DSS is the government standard defining DSA

Cryptographic Hashes & Message Digests

MD5
Calculates a 128 bit number from an input of any length
http://www.ietf.org/rfc/rfc1321.txt
http://userpages.umbc.edu/~mabzug1/cs/md5/md5.html

SHA & SHA-1
Calculate 160-bit number from input of any length
http://www.itl.nist.gov/fipspubs/fip180-1.htm
http://csrc.nist.gov/encryption/tkhash.html