![]() If we consider a triple length key to consist of three 56-bit keys K1, K2, K3 then encryption is as follows: Use of multiple length keys leads us to the Triple-DES algorithm, in which DES is applied three times. In fact, double length keys have been recommended for the financial industry for many years. ![]() Those who consider the exhaustive key-search attack to be a real possibility (and to be fair the technology to do such a search is becoming a reality) can overcome the problem by using double or triple length keys. Most reasonable people might find this rather comforting and a good measure of the strength of the algorithm. Assuming that the only feasible attack on DES is to try each key in turn until the right one is found, then 1,000,000 machines each capable of testing 1,000,000 keys per second would find (on average) one key every 12 hours. Ever since DES was first announced, controversy has taged about whether 56 bits is long enough to guarantee security. despite claims that the key length is too short. However, modern computers are so fast that satisfactory software implementations are readily available.ĭES is the most widely used symmetric algorithm in the world. The algorithm is best suited to implementation in hardware, probably to discourage implementations in software, which tend to be slow by comparison. However, it is usual to set each 8* bit so that each group of 8 bits has an odd number of bits set to 1. The key is always presented as a 64-bit block, every 8* bit of which is ignored. The algorithm uses a 56-bit key to encipher’decipher a 64-bit block of data. The following samples help to illustrate the depth and quality of this offering:ĭES (the Data Encryption Standard) is a symmetric block cipher developed by IBM. It enables you to understand the topic and is a handy reference guide for everyday use. Everything from the basic ‘what is cryptography? to ‘what does KEK mean?’ is covered. This is a concise yet extensive question and response summary of cryptography.
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