The type of cryptography in which the encryption process is publicly available and unprotected, but in which a part of the decryption key is protected so that only a party with knowledge of both parts of the decryption process can decrypt the cipher text. Note: Commonly called non-secret encryption in professional cryptologic circles. FIREFLY is an application of public key cryptography. 2. An Encryption system using a linked pair of keys. What one pair of keys encrypts, the other pair decrypts.