TIPS ： DES is fully known as data encryption standard, that is, data encryption standard. It is a block algorithm using key encryption. In 1977, it was determined as federal data processing standard (FIPS) by the National Bureau of standards of the federal government of the United States, and authorized to be used in unclassified government communications. Subsequently, this algorithm was widely spread internationally. It should be noted that in some literatures, des as an algorithm is called data encryption algorithm (DEA), which has been distinguished from des as a standard.