PGP stands for Pretty Good Privacy. It was created by Phil Zimmermann in 1991. PGP is a data encryption and decryption program that can be used for signing, encryption and decryption of texts, emails, files, directories or even whole disks.
PGP uses public key cryptography. The user first generates a keypair of a private and a public key. The private key is kept secret to the user, while the public key may be shared with someone who wants to communicate with the user.
When the user wants to share any text with a recepient, the user encrypts the text with the recepient's public key and sends it across. The recepient decrypts it with her private key and retrieves the message.
On the other hand, signing a text certifies and timestamps a document. Before sending a document to the recepient, the user can sign the document using her private key. The recepient, after receiving the document, can verify the signature using the public key of the signer. If the verification fails, that would mean, the document has been modified after signing it.
PGP uses public key cryptography much like DSA or RSA. But, unlike DSA or RSA, PGP gives the option of signing someone's public key with various level of trusts. Before using someone's public key, one can easily look into who all have signed the public key and with what level of trust. As a result, it becomes much difficult for attackers to forge someone's public key and to trick others to use it.
This is an introductory article. You can click on the links below to get more information.
How to install GPG ? (GnuPG is a complete and free implementation of the OpenPGP standard as defined by PGP)
Happy learning !