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The Zimmermann Telegram (as it was sent from Washington to Mexico) encrypted as ciphertext. KGB ciphertext found in a hollow nickel in Brooklyn in 1953. In cryptography, ciphertext or cyphertext is the result of encryption performed on plaintext using an algorithm, called a cipher. [1]
Codes operated by substituting according to a large codebook which linked a random string of characters or numbers to a word or phrase. For example, "UQJHSE" could be the code for "Proceed to the following coordinates." When using a cipher the original information is known as plaintext, and the encrypted form as ciphertext. The ciphertext ...
The adversary receives the encryption of m b, and attempts to "guess" which plaintext it received, and outputs a bit b'. A cipher has indistinguishable encryptions under a chosen-plaintext attack if after running the above experiment the adversary can't guess correctly (b=b') with probability non-negligibly better than 1/2. [3]
Plaintext is used as input to an encryption algorithm; the output is usually termed ciphertext, particularly when the algorithm is a cipher. Codetext is less often used, and almost always only when the algorithm involved is actually a code .
Cryptography prior to the modern age was effectively synonymous with encryption, converting readable information to unintelligible nonsense text , which can only be read by reversing the process . The sender of an encrypted (coded) message shares the decryption (decoding) technique only with the intended recipients to preclude access from ...
The Vigenère cipher uses a Caesar cipher with a different shift at each position in the text; the value of the shift is defined using a repeating keyword. [14] If the keyword is as long as the message, is chosen at random , never becomes known to anyone else, and is never reused, this is the one-time pad cipher, proven unbreakable.
The KL-7, introduced in the mid-1950s, was the first U.S. cipher machine that was considered safe against known-plaintext attack. [8]: p.37 Classical ciphers are typically vulnerable to known-plaintext attack. For example, a Caesar cipher can be solved
In Office 2007, protection was significantly enhanced by using AES as a cipher. [4] Using SHA-1 as a hash function, the password is stretched into a 128-bit key 50,000 times before opening the document; as a result, the time required to crack it is vastly increased, similar to PBKDF2, scrypt or other KDFs.