PGP Summary

PGP is software that allows for encryption and digital signing of documents. PGP is an acronym that stands for Pretty Good Privacy. It was created by Phil Zimmermann in 1991. Later PGP versions have been developed and distributed by MIT, ViaCrypt, Network Associates Inc and PGP Inc.

PGP uses a pair of keys that are closely associated with each other. One is a private key, the other is a public key. As the names imply, the private key is to be kept secret, while the public key should be freely distributed. The key pair works together by allowing any document signed or encrypted with the private key to be verified or decrypted with the public key. And the inverse is also true, any document signed or encrypted with the public key can be verified or decrypted with the private key. PGP allows for encryption and/or digital signatures.

A digital signature is a mathematical calculation on the content of a message, referred to as a message digest or one way hash. A message signed with a PGP private key can be verified with the public key. Verification allows an individual to be confident that the message was not altered in transit and that it is from the person or keyholder identified. Verification of a digital signature is optional and the content of the message can be viewed regardless of PGP use.

Digital signatures do not hide or change the content of messages. Encryption is used to hide and encode a message. A message encrypted with a PGP private key requires that the public key be used to decrypt it or it will be unreadable. Messages encrypted with the public key require the private key to decrypt it or it will be unreadable.

PGP provides substantial benefits with regard to authenticity, integrity and confidentiality. Digital signatures can be used to verify authenticity and integrity. That is, digital signatures allow an individual to be confident a message is, in fact, from who signed it and that the message is exactly the same as when it was signed, i.e., that was not altered in transit. Review the sample messages below for additional details. Also, review this HOWTO for instructions on how to install and verify a message with the freeware or demo version of PGP.

Example of the verification of a signed message:

Example of encrypted message:

Example of the decrypted results of the previously encrypted message: