A Course in Mathematical Cryptography

7 Public Key Cryptography

7.1 Public Key Cryptography

There are many instances where secure information must be sent over open communication lines. These include, for example, banking and financial transactions, purchasing items via credit cards over the internet, and similar things. This type of cryptographic communication is handled by public key cryptography in which both the encryption technique and the encrypted ciphertext are open to everyone but the encrypted transmission is considered secure.

Roughly, in classical cryptography only the sender and receiver know the encoding and decoding methods. Further it is a feature of such cryptosystems, such as the ones that we’ve already looked at, that if the encrypting method is known, then the ...