Over the years, various new block cipher algorithms have been designed as alternatives to DES. One is FEAL, a cipher for which numerous attacks have been discovered. IDEA is a cipher designed by Lai and Massey that seems much more promising and two more recent designs are RC5 and SAFER. In addition, the U.S. government announced in 1993 an algorithm called Skipjack as part of its Capstone project. Skipjack operates on 64-bit blocks of data, as does DES, but uses 80-bit keys, as opposed to the 56-bit keys in DES. However, the details of Skipjack are classified, so Skipjack is only available in hardware from government-authorized manufacturers.