Q: what is PGP?

A:

PGP combines some of the best features of both conventional and public key cryptography. PGP is a hybrid cryptosystem.When a user encrypts plaintext with PGP, PGP first compresses the plaintext. Data compression saves modem transmission time and disk space and, moreimportantly, strengthens cryptographic security. Most cryptanalysis techniques exploit patterns found in the plaintext to crack the cipher.Compression reduces these patterns in the plaintext, thereby greatly enhancing resistance to cryptanalysis. (Files that are too short to compress orwhich don’t compress well aren’t compressed.)

PGP then creates a session key, which is a one-time-only secret key. This key is a random number generated from the random movements of your mouse andthe keystrokes you type. This session key works with a very secure, fast conventional encryption algorithm to encrypt the plaintext; the result isciphertext. Once the data is encrypted, the session key is then encrypted to the recipient’s public key. This public key-encrypted session key is transmittedalong with the ciphertext to the recipient.

The combination of the two encryption methods combines the convenience of public key encryption with the speed of conventional encryption.Conventional encryption is about 1,000 times faster than public key encryption. Public key encryption in turn provides a solution to keydistribution and data transmission issues. Used together, performance and key distribution are improved without any sacrifice in security. to be continue............