PGP, or Pretty Good Privacy, is a security software application used for the encryption and decryption of data. In 1991, Philip R. Zimmermann wrote PGP for the purpose of sending secured data across an insecure network, such as the Internet. Individuals, businesses, and governments use strong cryptography programs such as PGP to secure networks, e-mails, documents, and stored data.

PGP was originally designed as a combination of RSA encryption and a symmetric key cipher known as Bass-O-Matic. RSA is a public key cryptographic algorithm named after its designers Ronald Rivest, Adi Shamir, and Leonard Adleman. The RSA algorithm developed in 1977 (earlier versions of which were partially developed by intelligence agencies) quickly became a major advancement in cryptology. The RSA algorithm depends upon the difficulty in factoring very large composite numbers and is currently the most commonly used encryption and authentication algorithm in the...