Pretty Good Privacy (PGP) is an encryption program privacy and authentication for data communication. PGP is used for signing encrypting, and decrypting texts, e-mails, files, directories, and whole disk partitions and to increase the security of e-mail communications.
PGP encryption uses a serial combination of hashing, data compression, symmetric-key cryptography, and finally public-key cryptography; each step uses one of several supported algorithms. Each public key is bound to a username or an e-mail address. The first version of this system was generally known as a web of trust