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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.
The parameters of the puzzle game can be chosen to make it considerably harder to for an eavesdropper to break the code than for the parties to communicate, but Merkle puzzles do not provide the enormous qualitative differences in difficulty that are required for (and define) security in modern cryptography.
The Massey–Omura method uses exponentiation in the Galois field GF(2 n) as both the encryption and decryption functions. That is E(e,m)=m e and D(d,m)=m d where the calculations are carried out in the Galois field. For any encryption exponent e with 0<e<2 n-1 and gcd(e,2 n-1)=1 the corresponding decryption exponent is d such that de ≡ 1 ...
Another method of substitution cipher is based on a keyword. All spaces and repeated letters are removed from a word or phrase, which the encoder then uses as the start of the cipher alphabet. The end of the cipher alphabet is the rest of the alphabet in order without repeating the letters in the keyword.
Polygraphic substitution is a cipher in which a uniform substitution is performed on blocks of letters. When the length of the block is specifically known, more precise terms are used: for instance, a cipher in which pairs of letters are substituted is bigraphic.
The concept of public key cryptography was introduced by Whitfield Diffie and Martin Hellman in 1976. [3] At that time they proposed the general concept of a "trap-door one-way function", a function whose inverse is computationally infeasible to calculate without some secret "trap-door information"; but they had not yet found a practical example of such a function.
Functions that lack this property are vulnerable to pre-image attacks. Second pre-image resistance: given an input m 1, it should be hard to find another input m 2 ≠ m 1 such that hash(m 1) = hash(m 2). This property is sometimes referred to as weak collision resistance. Functions that lack this property are vulnerable to second pre-image ...
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).