Capstone is the name of a United States government long-term project to develop cryptography standards for public and government use. Capstone was driven by the NIST and the NSA; the project began in 1993[1]. The initiative involved four standard algorithms: a data encryption algorithm called Skipjack, along with the Clipper chip that included the Skipjack algorithm, a digital signature algorithm, DSA, a hash function, SHA-1, and a key exchange protocol.[2] Captstone's first implementation was in the Fortezza PCMCIA card.
The initiative encountered massive resistance from the cryptographic community, and eventually the US government abandoned the effort. The main reasons for this resistance were concerns about Skipjack's design, which was classified, and the use of key escrow in the Clipper chip.