Acrónimos: CTR
Ver:
· [NIST-SP800-38A:2001]
· [FIPS-81:1980]
· Criptografía de clave secreta
· http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation
Al igual que el modo OFB, el modo CTR transforma un algoritmo de cifrado por bloques en un algoritmo de cifrado de flujo. La máscara de cifrado se genera cifrando un contador. Además de las ventajas del modo OFB, permite un acceso aleatorio a la información.
(N) A block cipher mode that enhances ECB mode by ensuring that each encrypted block is different from every other block encrypted under the same key. [SP38A] (See: block cipher.) [RFC4949:2007]
Like OFB, counter
mode turns a block cipher into a stream cipher. It generates the next keystream
block by encrypting successive values of a "counter". The counter can
be any simple function which produces a sequence which is guaranteed not to
repeat for a long time, although an actual counter is the simplest and most
popular. CTR mode has similar characteristics to OFB, but also allows a random
access property during decryption, and is believed to be as secure as the block
cipher being used. Note that the nonce in this graph is the same thing as the
initialization vector (IV) in the other graphs. The IV/nonce and the counter
can be concatenated, added, or XORed together to produce the actual unique
counter block for encryption.
http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation
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