DES - The Data Encryption Standard

The DES has provided federal standard for data encryption for the past thirty years. Originally developed in the 1970's by IBM, it uses a 56-bit "key" during execution. When used for communication, both the sender and the receiver must know the same secret key, which is used to both encrypt and then to decrypt the message.

DES is a block cipher; it takes a fixed-length string of plain text bits and uses a series of complicated operations to transform it into a ciphertext bitstring of the same length. Here's what the National Institute of Standards and Technology has to say about DES:

The cryptographic algorithm specified in this standard transforms a 64-bit binary value into a unique 64-bit binary value based on a 56-bit variable. If the complete 64-bit input is used (i.e., none of the input bits should be predetermined from block to block) and if the 56-bit variable is randomly chosen, no technique other than trying all possible keys using known input and output for the DES will guarantee finding the chosen key. As there are over 70,000,000,000,000,000 (seventy quadrillion) possible keys of 56 bits, the feasibility of deriving a particular key in this way is extremely unlikely in typical threat environments. Moreover, if the key is changed frequently, the risk of this event is greatly diminished. However, users should be aware that it is theoretically possible to derive the key in fewer trials (with a correspondingly lower probability of success depending on the number of keys tried) and should be cautioned to change the key as often as practical. Users must change the key and provide it a high level of protection in order to minimize the potential risks of its unauthorized computation or acquisition. The feasibility of computing the correct key may change with advances in technology.
(From Data Encryption Standard.)
In 1999, DES was successfully broken by the Electronic Frontier Foundation; however, the effort required is beyond the means of individuals and most corporations today. Some former DES users make use of Triple-DES, which involves applying DES three times with different keys. TDES is regarded as adequately secure, but slow.

In November 2001, the US government adopted a new standard, the Advanced Encryption Standard (AES).

Index of related articles:

What is encryption?
DES - The Data Encryption Standard
AES - The Advanced Encryption Standard








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