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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 ...
In Excel and Word 95 and prior editions a weak protection algorithm is used that converts a password to a 16-bit verifier and a 16-byte XOR obfuscation array [1] key. [4] Hacking software is now readily available to find a 16-byte key and decrypt the password-protected document. [5] Office 97, 2000, XP and 2003 use RC4 with 40 bits. [4]
Information—a message, document, file, etc.—if to be communicated or stored in an unencrypted form is referred to as plaintext. Plaintext is used as input to an encryption algorithm ; the output is usually termed ciphertext , particularly when the algorithm is a cipher .
Public-key encryption was first described in a secret document in 1973; [15] beforehand, all encryption schemes were symmetric-key (also called private-key). [ 16 ] : 478 Although published subsequently, the work of Diffie and Hellman was published in a journal with a large readership, and the value of the methodology was explicitly described ...
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 ...
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 ...
While solving a monoalphabetic substitution cipher is easy, solving even a simple code is difficult. Decrypting a coded message is a little like trying to translate a document written in a foreign language, with the task basically amounting to building up a "dictionary" of the codegroups and the plaintext words they represent.
Red/black box. The red/black concept, sometimes called the red–black architecture [1] or red/black engineering, [2] [3] refers to the careful segregation in cryptographic systems of signals that contain sensitive or classified plaintext information (red signals) from those that carry encrypted information, or ciphertext (black signals).