[INLINE]
     
                             FOR IMMEDIATE RELEASE
                                April 16, 1998
       ______________________________________________________________
     
NTT Develops Secure Public-Key Encryption Scheme

     Nippon Telegraph and Telephone Corporation (NTT) announced today
     the development of Efficient Probabilistic Public-Key Encryption
     (EPOC), a highly secure and mathematically verified public-key
     encryption scheme that encrypts information on the transmission
     side with a public-key (encryption key) and then decrypts it on the
     receiver side with a secret -key (decryption key). Encryption
     technology has become necessary to prevent information on the
     Internet from being monitored by others without authorization.
     Public-key encryption is being widely researched as a practical
     means of encrypting communication for security. The paramount
     feature of any public-key encryption schemes is ensuring that
     figuring out the decryption key from the encryption key is as
     difficult as possible, to prevent unauthorized use of ciphered
     information. The RSA*1 scheme uses factoring and the elliptic curve
     encryption scheme*2 uses elliptic curve discrete logarithms, both
     of which can take a supercomputer a very long time to determine the
     key. It has not been verified, however, that either scheme provides
     the necessary security to prevent ciphered information from being
     broken by a method other than factoring or elliptic curve discrete
     logarithms. The Rabin encryption scheme*3, which also uses
     factoring, offers no algorithm other than factoring for computing
     the complete plain-text, but it has not been proven that any bit of
     plain-text cannot be computed. EPOC is a practical scheme in that
     the computer computation workload for encrypting and decrypting is
     about the same as that for the RSA and elliptic curve encryption
     schemes. Also, EPOC is a highly secure scheme which uses a trapdoor
     discrete logarithm*4 as the key mathematical technique and can be
     broken only by factoring. Factoring is difficult to accomplish,
     even with a supercomputer, and the probability that an efficient
     solution to factoring will be found soon is very low, because
     mathematicians have been studying the problem for years. EPOC
     ensures that partial, as well as whole, texts cannot be broken.
     Finally, EPOC uses probabilistic encryption, so re-encrypted text
     is encrypted differently each time, unlike the Rabin and RSA
     scheme, which use deterministic encryption. NTT now plans to
     incorporate EPOC in systems for enhanced security on the Internet.
     Public-key encryption is used primarily for key distribution,
     because computation load is greater than that for secret-key
     encryption*5, so EPOC will be used in existing encryption modules
     for key distribution. Other applications will also be developed. In
     particular, EPOC is suitable for electronic voting and anonymous
     telecommunication since it has a homomorphic property, unlike the
     RSA, Rabin and elliptic curve encryption schemes. The theoretical
     details will be presented at Eurocrypt '98 in Finland this June.
     Notes: *1: The RSA scheme was developed by Rivest, Shamir, and
     Adleman in 1978 and is based on the difficulty of factoring. It was
     the first public-key encryption scheme. *2: The elliptic curve
     encryption scheme was proposed independently by Miller and Koblitz
     in 1985 and is based on the difficulty of elliptic curve discrete
     logarithms. The basic technique is based on a scheme developed by
     Diffie and Hellman in 1976. *3: The Rabin scheme was developed by
     Rabin in 1979 and is based on the difficulty of factoring. It was
     the first public-key encryption scheme to verify the impossibility
     of breaking a complete text without factoring the public-key. *4: A
     trapdoor discrete logarithm is a newly discovered discrete
     logarithm problem that can be solved only if a secret-key is known.
     *5: Secret-key encryption differs from public-key encryption in
     that the sender and the receiver use the same key for encryption
     and decryption.
     
                                 [1][LINK]
                              NTT NEWS RELEASE

References

   1. http://www.ntt.co.jp/news/indexe.html