An integrated circuit that uses the Skipjack voice encryption algorithm developed by the United States National Security Agency (NSA) for the National Institute of Science and Technology (NIST). Skipjack is a block coding algorithm that encrypts 64-bit data blocks with an 80-bit key. Data encrypted by the Skipjack algorithm can be provided not only to the intended recipient through the use of a key, but also by the U.S. government through the use of a back door into a Law Enforcement Access Field (LEAF).The Clipper Chip is manufactured by the U.S. government, which has tried unsuccessfully to make it, and similar technologies, mandatory for voice encryption in the United States. Privacy advocates feared that government authorities would abuse the back door. Law enforcement authorities fear that the widespread use of other voice encryption technologies will make it impossible to place legal wiretaps. See also algorithm, back door, encryption, integrated circuit, and wiretap.