CAST5
CAST5 (or CAST-128) was created by Carlisle Adams and Stafford Tavares in 1996. It defines a symmetric key method that has a 64-bit block size, and key sizes from 40 bits up to 128 bits (in jumps of 8 bits). Typically any key less than 80 bits would be seen as being insecure. It uses a 12- or 16-round Feistel cipher. The 16-round version is used for keys for 80 bits and above. It has been standardized in RFC2612 [here]:
Phil Zimmerman could not believe there was no real security or trust built into email. So, in 1991, he created PGP (Pretty Good Privacy). With this, Bob creates a random symmetric key, which is used to encrypt a message. Bob then encrypts this symmetric key with Alice’s public key. When she receives the email she discovers the symmetric key with her private key and then decrypts the message:
But, Phil’s code then appeared outside the US, and in 1993 he was involved in a criminal investigation “munitions export without a license. While this was underway, his team released PGP 3, which improved the overall security of the software. With this, the team avoided…
