Data Encryption Standard

Introduction

In 1972, the National Institute of Standards and Technology (NIST), then know by the name National Bureau of Standards, requested proposals for a cryptographic algorithm that could be used to protect non-classified information.They wanted the algorithm to be very secure, inexpensive, easy to understand and adaptable for diverse applications so that the algorithm could be used by different institutions and by the general public. 

In 1974 they made the request again as they did not receive any viable proposals in 1972. This time IBM submitted the Lucifer algorithm. The algorithm was forwarded to the National Security Agency (NSA) to evaluate its security. NSA made some modifications to the algorithms with the most important one being the replacement of a 128-bit key with a 56-bit key. 

Many people suspected that the modifications made by the NSA were deliberate to make the algorithm weak and add a back door so that its agents would be able to decrypt the encrypted messages without the key. Ignoring such suspicions, NIST adopted the modified algorithm as a federal standard in November 1976. The algorithm name was changed to the Data Encryption Standard and published in January 1977 as FIPS PUB 46. Since then it has been a widely used cryptographic algorithm for various application and the suspicions slowly faded away as no one was able to find a back door to attack DES. 

Over the years, computers have become more powerful and various brute-force attacks on the DES undermined its capabilities as a powerful and secure cryptosystem. In 1997, NIST abandoned its official endorsment of DES as a federal standard and started to work on a new algorithm called the Advanced Encryption Standard that would replace DES.