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An attacker should not be able to find the key used in a modern cipher, even if they know any specifics about the plaintext and its corresponding ciphertext. Modern encryption methods can be divided into the following categories: Private-key cryptography (symmetric key algorithm): one shared key is used for encryption and decryption
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 .
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 ...
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 ...
Originating from the Arabic word for zero صفر (ṣifr), the word "cipher" spread to Europe as part of the Arabic numeral system during the Middle Ages. The Roman numeral system lacked the concept of zero, and this limited advances in mathematics. In this transition, the word was adopted into Medieval Latin as cifra, and then into Middle ...
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]
This is equivalent to the expectation that encryption schemes exhibit an avalanche effect. The purpose of diffusion is to hide the statistical relationship between the ciphertext and the plain text. For example, diffusion ensures that any patterns in the plaintext, such as redundant bits, are not apparent in the ciphertext. [3]
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).