Efficient Probabilistic Public-Key Encryption Scheme


EPOC is a probabilistic public-key encryption scheme.
EPOC was developed in 1999 by T. Okamoto, S. Uchiyama and E. Fujisaki of NTT Labs in Japan. It is based on the random oracle model, in which a primitive public-key encryption function is converted to a secure encryption scheme by use of a truly random hash function; the resulting scheme is designed to be semantically secure against a chosen ciphertext attack.
EPOC's primitive encryption function is the OU function, in which to invert the OU function is proven to be as hard as factoring a composite integer public key. There are three versions of EPOC:
EPOC-1 is designed for key distribution; EPOC-2 and EPOC-3 are designed for both key distribution and encrypted data transfer.