Pretty Good Privacy (PGP)

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PRETTY GOOD PRIVACY - PGP
Pretty Good Privacy, commonly called PGP, is a freely available cryptographic program developed by Philip Zimmerman for the purpose of providing security (confidentiality and authentication) in data communication. It is mostly employed by most email applications as it can be used for signing, encrypting, and decrypting messages and files.
Operational Design of PGP
PGP was designed in a way to operate in a manner that satisfies four different services: digital signature/ authentication, message encryption/ confidentiality, compression and email compatibility.
1. Authentication/ Digital signature: Hash code (created using SHA-1) of a message is encrypted with the sender’s secret key (using DSS or RSA) and included with the message.
The recipient decrypts with the …show more content…

• Various implementations of the algorithms operate well together as one version of the algorithm can decompress some other version. Signing after compression would impede all implementations to the same version, making it incompatible with any other version.
It is compressed before encryption to strengthen its security against cryptanalytic attacks as compression reduces redundancy, thus, encrypting an already reduced redundant message makes the encryption even stronger.
4. Email compatibility: PGP converts the default 8-bit binary stream of text to ASCII text the standard allowed format of characters allowed in most email systems.
To make this conversion, radix-64 is used. Radix-64 does this by mapping every group of 3 octets of binary data into 4 ASCII characters.
Overview of the Design On transmission: generate signature using hash code of uncompressed plaintext then compress the plaintext with the signature. Afterwards, you encrypt and attach the public key and finally convert the entire block to radix-64

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