PGP (Pretty Good Privacy)

It combines the best cryptographic algorithms tto achieve secure e-mail comunication.

PGP applies compression after signing and before encryption.

Symmetric Keys

Same key used in encryption and Decryption. If A wants to send encrypted messages to B, they must have the same key (so one of them must send it unencrypted to the other not safe).

AES (Advanced Encryption Standard)

Symetric keys using the Rijndael algorithm.

Asymmetric Encryption

Two related keys (one private key known only to the individual and a public key available to anyone). It implements confidentiality by enciphering using public key and deciphering using private key and interity/authentication using private key to encipher and public to decipher.

Private keys must be infeasible to derive from public keys.

RSA

Best known & widely used public-key scheme.

Direct Digital Signature

• Encrypt-Sign: Signatures can be easily replaced
• Sign-Encrypt: Recipient knows who wrote the message but not who encrypted it