Since the introduction of the Data EncryptionStandard (DES) in the mid 1970s, cryptanalysts have been increasingly concerned about the 56-bit secret key used in the cipher and its vulnerability to exhaustive key search. In 1977, Diffie and Hellman  estimated the cost of a machine capable of recovering a 56-bit key within a day at US$20 million. In 1993, Wiener provided a detailed design for a machine which would reduce the average search time to 3.5 hours . The design consisted of 57,000 custom chips and had an estimated cost of US$1 million. Half a decade later, the Electronic Frontier Foundation (EFF) actually built the first search machine. The US$250,000 machine was called “Deep Crack”  and ran through the complete key space in nine days.
As it became clear that DES did not provide adequate security because of its 56-bit secret key, the cipher was gradually replaced by Triple-DES (also known as TDEA). Triple-DES is a multipleencryptionscheme. The idea of triple...
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