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In cryptography, a cipher (or cypher) is an algorithm for performing encryption or decryption —a series of well-defined steps that can be followed as a procedure. An alternative, less common term is encipherment. To encipher or encode is to convert information into cipher or code. In common parlance, "cipher" is synonymous with "code", as ...
Classical cipher. In cryptography, a classical cipher is a type of cipher that was used historically but for the most part, has fallen into disuse. In contrast to modern cryptographic algorithms, most classical ciphers can be practically computed and solved by hand. However, they are also usually very simple to break with modern technology.
Caesar cipher. The action of a Caesar cipher is to replace each plaintext letter with a different one a fixed number of places down the alphabet. The cipher illustrated here uses a left shift of 3, so that (for example) each occurrence of E in the plaintext becomes B in the ciphertext. In cryptography, a Caesar cipher, also known as Caesar's ...
Copiale cipher: Solved in 2011 1843 "The Gold-Bug" cryptogram by Edgar Allan Poe: Solved (solution given within the short story) 1882 Debosnys cipher: Unsolved 1885 Beale ciphers: Partially solved (1 out of the 3 ciphertexts solved between 1845–1885) 1897 Dorabella Cipher: Unsolved 1903 "The Adventure of the Dancing Men" code by Arthur Conan ...
For example, in a Caesar cipher of shift 3, a would become D, b would become E, y would become B and so on. The Vigenère cipher has several Caesar ciphers in sequence with different shift values. To encrypt, a table of alphabets can be used, termed a tabula recta, Vigenère square or Vigenère table. It has the alphabet written out 26 times in ...
Transposition cipher. Step-by-step process for the double columnar transposition cipher. In cryptography, a transposition cipher (also known as a permutation cipher) is a method of encryption which scrambles the positions of characters (transposition) without changing the characters themselves. Transposition ciphers reorder units of plaintext ...
Ciphertext is also known as encrypted or encoded information because it contains a form of the original plaintext that is unreadable by a human or computer without the proper cipher to decrypt it. This process prevents the loss of sensitive information via hacking. Decryption, the inverse of encryption, is the process of turning ciphertext into ...
Cryptanalysis of symmetric-key ciphers typically involves looking for attacks against the block ciphers or stream ciphers that are more efficient than any attack that could be against a perfect cipher. For example, a simple brute force attack against DES requires one known plaintext and 2 55 decryptions, trying approximately half of the ...