حل تشریحی سوال شماره 30 زبان عمومی و تخصصی (انگلیسی)

The Data Encryption Standard, affectionately known as DES-which rhymes with "fez" and "pez" was developed way back in the 1970s. The design is based on the Lucifer cipher, a Feistel cipher developed by IBM. DES is a surprisingly simple block cipher, but the story of how Lucifer became DES is anything but simple. By the mid-1970, it was clear even to U.S. government byreaucrats that there was a legitimate cooercial need for secure crypto. At the time, the computer revolution was underway, and the ampunt- and sensitivity - of digital data was rapidly increasing. In the mid-1970s, crypto was poorly understood outside of classified military and government circles. The upshot was that businesses had no way to judge the merits of a crypto product and the quality of most such products was very poor. Into environment, the National Bureau of Standards, or NBS (now Known as NIST) issued a request for cipher proposals. The winning submission would become a U.S. government standard and almost certainly a de facto industrial standard. Very few reasonable submissions were received, and it quickly became apparent that IBM's Lucifer cipher was the only serious contender. At this point, NBS had a problem. There was little crypto expertise at NBS, so they turned to the government's crypto experts, the super-secret National Security Agency, or NSA. The NSA designs and builds the crypto that is used by the U.S. military and government for highly sensitive information. The NSA also conducts "signals intelligence," or SIGINT, where it tries to obtain intelligence information. The NSA was apparently reluctant to get involved with DES but eventually agreed to study the Lucifer design and offer an opinion. This all happened in secret, and when the information later came to public light, many were suspicious that NSA had placed a "backdoor" into DES so that it alone could easily break the cipher. Certainly, the SIGINT mission of NSA and a general climate of distrust of government fuelet such fears. But it's worth noting that 30 years of intense cryptanalysis gas revealed no backdoor in DES. Nevertheless, this suspicion tainted DES from its inception.