Computer Security and Cryptography

9.12 WHAT NOW?

If the key length were 2⁶⁴ it would have taken the DES-cracker 768 days; if the key length were 2 × 56, the DES-cracker would have to work a very long time to find the key. This points out the power of exponentiation and the advantage enjoyed by the designer of a cryptosystem over the cryptanalyst. Adding one bit to the key doubles the time for exhaustive search. If the designers of DES had been careless and there was some intrinsic weakness, or a trap-door, such a statement would not necessarily be true.

Walter Tuchman of IBM's Kingston Facility was a designer and implementor of DES. He also proposed triple DES [FIPS PUB 46-3, 1999] defined by²

If k₁ = k₂, DES3 reduces to ordinary DES.

The U.S. Munitions List is part of the secondary regulations (the International Traffic in Arms Regulations or ITAR) that defines which defence articles and services are subject to licensing. Cryptographic products are included in the products (Category XIII – Auxiliary Military Equipment) regulated by ITAR.

Current export rules do not permit the export of DES3 to certain countries. An article in the Wall Street Journal (September 17, 1998) entitled “Encryption Export Rules Relaxed” claims that the current 56-bit limitation will be relaxed, asserting

U.S. vendors also won more freedom to export network-encryption products used primarily by Internet-service provides and communication ...