Identify and Describe the Weaknesses of the Data Encryption Standard DES Algorithm

¶ … weaknesses of the Data Encryption Standard (DES).

The Data Encryption Standard (DES) was a system developed by the USD government for use by the general public. Accepted both by the U.S. And abroad, many hardware and software systems employ the DES. Both individuals can send and encrypt and decrypt information to and from the other. The symmetry of the situation makes this a popular key. Authenticity is guaranteed since only the sender can produce a message that will encrypt with the shared key (Paar, & Pelzl, 2009). However the DES is also riddled by various weaknesses (Pfleeger & Pfleeger, 2007).

Firstly and, perhaps, most importantly, security is a major concern. Whilst issues have been more or less resolved regarding the design's secrecy and that certain 'trapdoors' had been embedded in the DES algorithm enabling easy means to decrypt the message, many analysts are still concerned about the number of iterations considering 16 iterations to be insufficient in diffusing the information. Most serious of all, however, is the length of the key, which is only 56 bits long (compared to the key in the original IBM transfiguration which was 128 bits). The shortness of the key could challenge security. Nonetheless, different strategies have been successfully developed to deal with this problem.

Other weaknesses of the DES focus on the algorithm itself. Firstly, there is the problem of complements. Complements refer to the case where 1s in a binary number replaces all 1s by 0s and all 0s. When a message is encrypted with a particular key, complement of that encryption will register as encryption of the message possibly confusing it. However, since most encryption messages do not involve or trigger complement response and since users can be warned not to use complement keys, this is not such a significant issue.

A second concern involves ' weak keys'. The initial key is split into two halves with both halves independently shifted circularly. If the value being shifted is either all 0s or all 1s, the key used for encryption will be the same in all other cycles; potentially confusing encryption with decryption since some keys (called 'weak keys') share the same task. However, these keys are known and therefore too do not pose a problem.

Similarly, too, is the case of 'semiweak keys' where specific keys have identical decryption. Users of the Data Encryption Standard (DES) are simply advised to be aware of these keys and when possible to avoid them.

Design weakness of the algorithm is another slight limitation where expansion permutation of the algorithm repeats the first and fourth bits of every 4-bit series, replacing bits from the neighboring 4-bits series. This is only a minor concern, but one wonders whether similar problems may not be inherent elsewhere in the algorithm.

Another concern is that of 'key clustering' where it is posited quite likely that two different keys generate the same encryption. The analysis to investigate this is complex and involved, but researchers found key clustering (i.e. cipher texts that produced identical plaintext) when looking through three cycles of the DES (Pfleeger & Pfleeger, 2007).