Email Security Guidelines, Encryption and Appliances Definitions

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  • A

    Advanced Encryption Standard (AES)

    The Advanced Encryption Standard, or AES, is a symmetric block cipher used by the U.S. government to protect classified information and is implemented in software and hardware throughout the world to encrypt sensitive data.

  • anonymous email

    Anonymous e-mail is e-mail that has been directed to a recipient through a third-party server that does not identify the originator of the message.

  • B

    block cipher

    A block cipher is a method of encrypting text (to produce ciphertext) in which a cryptographic key and algorithm are applied to a block of data (for example, 64 contiguous bits) at once as a group rather than to one bit at a time.

  • C

    chaffing and winnowing

    Chaffing and winnowing are dual components of a privacy-enhancement scheme that does not require encryption.

  • challenge-response system

    A challenge-response system is a program that replies to an e-mail message from an unknown sender by subjecting the sender to a test (called a CAPTCHA) designed to differentiate humans from automated senders.

  • cipher

    A cipher (pronounced SAI-fuhr) is any method of encrypting text (concealing its readability and meaning).

  • cipher block chaining (CBC)

    Cipher block chaining (CBC) is a mode of operation for a block cipher (one in which a sequence of bits are encrypted as a single unit or block with a cipher key applied to the entire block).

  • ciphertext feedback (CFB)

    Ciphertext feedback (CFB) is a mode of operation for a block cipher. In contrast to the cipher block chaining (CBC) mode, which encrypts a set number of bits of plaintext at a time, it is at times desirable to encrypt and transfer some plaintext values instantly one at a time, for which ciphertext feedback is a method.

  • cryptanalysis

    Cryptanalysis refers to the study of ciphers, ciphertext, or cryptosystems (that is, to secret code systems) with a view to finding weaknesses in them that will permit retrieval of the plaintext from the ciphertext, without necessarily knowing the key or the algorithm.

  • crypto

    Depending on its usage, crypto can be a short form for cryptography or for encryption.

  • cryptographic checksum

    A cryptographic checksum is a mathematical value (called a checksum) that is assigned to a file and used to "test" the file at a later date to verify that the data contained in the file has not been maliciously changed.

  • cryptology

    Cryptology is the mathematics, such as number theory, and the application of formulas and algorithms, that underpin cryptography and cryptanalysis.

  • cryptoperiod (key lifetime or a validity period)

    A cryptoperiod (sometimes called a key lifetime or a validity period) is a specific time span during which a cryptographic key setting remains in effect.

  • cut-and-paste attack

    A cut-and-paste attack is an assault on the integrity of a security system in which the attacker substitutes a section of ciphertext (encrypted text) with a different section that looks like (but is not the same as) the one removed.

  • D

    Data Encryption Standard (DES)

    The Data Encryption Standard (DES) is an outdated symmetric-key method of data encryption.