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The affine cipher is a type of monoalphabetic substitution cipher, where each letter in an alphabet is mapped to its numeric equivalent, encrypted using a simple mathematical function, and converted back to a letter. The formula used means that each letter encrypts to one other letter, and back again, meaning the cipher is essentially a ...
The book cipher is a type of homophonic cipher, one example being the Beale ciphers. This is a story of buried treasure that was described in 1819–21 by use of a ciphered text that was keyed to the Declaration of Independence. Here each ciphertext character was represented by a number.
The table below shows the support of various stream ciphers. Stream ciphers are defined as using plain text digits that are combined with a pseudorandom cipher digit stream. Stream ciphers are typically faster than block ciphers and may have lower hardware complexity, but may be more susceptible to attacks.
The Aristocrat Cipher is a type of monoalphabetic substitution cipher in which plaintext is replaced with ciphertext and encoded into assorted letters, numbers, and symbols based on a keyword. The formatting of these ciphers generally includes a title, letter frequency, keyword indicators, and the encoder's nom de plume . [ 1 ]
The Atbash cipher is a particular type of monoalphabetic cipher formed by taking the alphabet (or abjad, syllabary, etc.) and mapping it to its reverse, so that the first letter becomes the last letter, the second letter becomes the second to last letter, and so on. For example, the Hebrew alphabet would work like this:
In a route cipher, the plaintext is first written out in a grid of given dimensions, then read off in a pattern given in the key. For example, using the same plaintext that we used for rail fence: W R I O R F E O E E E S V E L A N J A D C E D E T C X The key might specify "spiral inwards, clockwise, starting from the top right".
Classical ciphers are typically vulnerable to known-plaintext attack. For example, a Caesar cipher can be solved using a single letter of corresponding plaintext and ciphertext to decrypt entirely. A general monoalphabetic substitution cipher needs several character pairs and some guessing if there are fewer than 26 distinct pairs.
All too common current examples are commercial security products that derive keys for otherwise impregnable ciphers like AES from a user-selected password. Since users rarely employ passwords with anything close to the entropy of the cipher's key space, such systems are often quite easy to break in practice using only ciphertext.