Modern PKC was first described publicly by Stanford University professor Martin Hellman and graduate student Whitfield Diffie in 1976.Their paper described a two-key crypto system in which two parties could engage in a secure communication over a non-secure communications channel without having to share a secret key. The biggest difficulty with this approach, of course, is the distribution of the key (more on that later in the discussion of public key cryptography).
The Advanced Encryption Standard (AES) and Rijndael 5.10. Because a single key is used for both functions, secret key cryptography is also called symmetric encryption.
The receiver applies the same key to decrypt the message and recover the plaintext.
Because a pair of keys are required, this approach is also called asymmetric cryptography.
In PKC, one of the keys is designated the public key and may be advertised as widely as the owner wants.
Stream ciphers operate on a single bit (byte or computer word) at a time and implement some form of feedback mechanism so that the key is constantly changing.