Tommy FlowersThomas Harold Flowers MBE (22 December 1905 – 28 October 1998) was an English engineer with the British General Post Office. During World War II, Flowers designed and built Colossus, the world's first programmable electronic computer, to help decipher encrypted German messages. Flowers was born at 160 Abbott Road, Poplar in London's East End on 22 December 1905, the son of a bricklayer. Whilst undertaking an apprenticeship in mechanical engineering at the Royal Arsenal, Woolwich, he took evening classes at the University of London to earn a degree in electrical engineering.
Preimage attackIn cryptography, a preimage attack on cryptographic hash functions tries to find a message that has a specific hash value. A cryptographic hash function should resist attacks on its (set of possible inputs). In the context of attack, there are two types of preimage resistance: preimage resistance: for essentially all pre-specified outputs, it is computationally infeasible to find any input that hashes to that output; i.e., given , it is difficult to find an such that () = .
Type B Cipher MachineIn the history of cryptography, the "System 97 Typewriter for European Characters" (九七式欧文印字機 kyūnana-shiki ōbun injiki) or "Type B Cipher Machine", codenamed Purple by the United States, was an encryption machine used by the Japanese Foreign Office from February 1939 to the end of World War II. The machine was an electromechanical device that used stepping-switches to encrypt the most sensitive diplomatic traffic. All messages were written in the 26-letter English alphabet, which was commonly used for telegraphy.
Linear cryptanalysisIn cryptography, linear cryptanalysis is a general form of cryptanalysis based on finding affine approximations to the action of a cipher. Attacks have been developed for block ciphers and stream ciphers. Linear cryptanalysis is one of the two most widely used attacks on block ciphers; the other being differential cryptanalysis. The discovery is attributed to Mitsuru Matsui, who first applied the technique to the FEAL cipher (Matsui and Yamagishi, 1992).
Avalanche effectIn cryptography, the avalanche effect is the desirable property of cryptographic algorithms, typically block ciphers and cryptographic hash functions, wherein if an input is changed slightly (for example, flipping a single bit), the output changes significantly (e.g., half the output bits flip). In the case of high-quality block ciphers, such a small change in either the key or the plaintext should cause a drastic change in the ciphertext. The actual term was first used by Horst Feistel, although the concept dates back to at least Shannon's diffusion.
Kasiski examinationIn cryptanalysis, Kasiski examination (also referred to as Kasiski's test or Kasiski's method) is a method of attacking polyalphabetic substitution ciphers, such as the Vigenère cipher. It was first published by Friedrich Kasiski in 1863, but seems to have been independently discovered by Charles Babbage as early as 1846. In polyalphabetic substitution ciphers where the substitution alphabets are chosen by the use of a keyword, the Kasiski examination allows a cryptanalyst to deduce the length of the keyword.
Key scheduleIn cryptography, the so-called product ciphers are a certain kind of cipher, where the (de-)ciphering of data is typically done as an iteration of rounds. The setup for each round is generally the same, except for round-specific fixed values called a round constant, and round-specific data derived from the cipher key called a round key. A key schedule is an algorithm that calculates all the round keys from the key. Some ciphers have simple key schedules.
