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Hill's cipher machine, from figure 4 of the patent. In classical cryptography, the Hill cipher is a polygraphic substitution cipher based on linear algebra.Invented by Lester S. Hill in 1929, it was the first polygraphic cipher in which it was practical (though barely) to operate on more than three symbols at once.
Lester S. Hill (1891–1961) was an American mathematician and educator who was interested in applications of mathematics to communications.He received a bachelor's degree (1911) and a master's degree (1913) from Columbia College and a Ph.D. from Yale University (1926).
The combination of wider and wider weak, linear diffusive steps like a Hill cipher, with non-linear substitution steps, ultimately leads to a substitution–permutation network (e.g. a Feistel cipher), so it is possible – from this extreme perspective – to consider modern block ciphers as a type of polygraphic substitution.
Unfortunately, the basic Hill cipher is vulnerable to a known-plaintext attack because it is completely linear. This claim is indeed somewhat ambiguous. However, it does not talk about the key space. Rather it refers to the observation that the encryption is a linear function. The consequence is that if an attacker knows some plaintext and the ...
This was followed up over the next fifty years with the closely related four-square and two-square ciphers, which are slightly more cumbersome but offer slightly better security. [1] In 1929, Lester S. Hill developed the Hill cipher, which uses matrix algebra to encrypt blocks of any desired length. However, encryption is very difficult to ...
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