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A plain language (or code) passage of any length, usually obtained by solving one or more cipher or code messages, and occurring or believed likely to occur in a different cipher or code message, which it may provide a means of solving. [1] [2] —
Polygraphic substitution cipher: the unit of substitution is a sequence of two or more letters rather than just one (e.g., Playfair cipher) Transposition cipher: the ciphertext is a permutation of the plaintext (e.g., rail fence cipher) Historical ciphers are not generally used as a standalone encryption technique because they are quite easy to ...
Javascrypt [8] Free open-source text encryption tool runs entirely in web browser, send encrypted text over insecure e-mail or fax machine. PyEyeCrypt [9] Free open-source text encryption tool/GUI with user-selectable AES encryption methods and PBKDF2 iterations. Signal Protocol. Google Allo (optional) Facebook Messenger (optional) Signal ...
Later Vula added a stream cipher keyed by book codes to solve this problem. [ 36 ] A related notion is the one-time code —a signal, used only once; e.g., "Alpha" for "mission completed", "Bravo" for "mission failed" or even "Torch" for " Allied invasion of French Northern Africa " [ 37 ] cannot be "decrypted" in any reasonable sense of the word.
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.
Encrypting an n-bit number so that the ciphertext is another n-bit number (this is the definition of an n-bit block cipher). For such finite domains, and for the purposes of the discussion below, the cipher is equivalent to a permutation of N integers {0, ... , N−1} where N is the size of the domain.
An autokey cipher (also known as the autoclave cipher) is a cipher that incorporates the message (the plaintext) into the key. The key is generated from the message in some automated fashion, sometimes by selecting certain letters from the text or, more commonly, by adding a short primer key to the front of the message.
Decryption is similar: the decryption algorithm takes, in this example, a 128-bit block of ciphertext together with the secret key, and yields the original 128-bit block of plain text. [ 4 ] For each key K , E K is a permutation (a bijective mapping) over the set of input blocks.