“Public” key ciphers rely on the recent (a few decades old) discovery of encryption functions with the following characteristics:
A different key is needed to decrypt information than the key used to encrypt it. See Figure 2-4.
It is computationally infeasible to determine the decryption key from the encryption key.
Knowing the encryption key offers no help in decryption. Knowing the decryption key offers no help in encryption.
This set of characteristics dramatically changes the security model in comparison with secret key ciphers. Some application that wants to receive confidential ...