3.6.1 What is Capstone?

  Capstone is the U.S. government's long-term project to develop a set of standards for publicly-available cryptography, as authorized by the Computer Security Act of 1987. The primary agencies responsible for Capstone are NIST and the NSA (see Section 7). The plan calls for the elements of Capstone to become official U.S. government standards, in which case both the government itself and all private companies doing business with the government would be required to use Capstone.

There are four major components of Capstone: a bulk data encryption algorithm, a digital signature algorithm, a key exchange protocol, and a hash function. The data encryption algorithm is called Skipjack (see Question 3.6.5), but is often referred to as Clipper, which is the encryption chip that includes Skipjack (see Question 3.6.2). The digital signature algorithm is DSS (see Question 3.6.8) and the hash function is SHS (see Question 3.8.4 about SHS and Question 3.8.2 about hash functions). The key exchange protocol has not yet been announced.

All the parts of Capstone have 80-bit security: all the keys involved are 80 bits long and other aspects are also designed to withstand anything less than an ``80-bit'' attack, that is, an effort of 2⁸⁰ operations. Eventually the government plans to place the entire Capstone cryptographic system on a single chip.