An interesting form of steganography, the subliminal channel, was used between the United States and the U.S.S.R. in 1978. During that time President Carter was heavily involved with the Strategic Arms Limitation Treaty (SALT) talks, which would systematically reduce the number of intercontinental ballistic missiles (ICBMs) between the superpowers. In order to do this to each party's satisfaction, there had to be a protocol in place that allowed the U.S.S.R. to verify the numbers of Minutemen missiles without revealing where the missiles were. This protocol would have to be digitally signed and incapable of being forged. At that time the United States had 100 Minutemen missiles and 1000 silos to hide them in, so it became a shell game of sorts: Keep the Minutemen but keep them safe from a first strike attack by not letting the U.S.S.R. know where they were located.