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Table compares implementations of block ciphers. Block ciphers are defined as being deterministic and operating on a set number of bits (termed a block) using a symmetric key. Each block cipher can be broken up into the possible key sizes and block cipher modes it can be run with.
CBC uses a random initialization vector (IV) to ensure that distinct ciphertexts are produced even when the same plaintext is encoded multiple times. The IV can be transmitted in the clear without jeopardizing security. A common practice is to prepend the 16 byte IV to the ciphertext, which gives the decrypter easy access to the IV.
training key - (NSA) unclassified key used for instruction and practice exercises. Type 1 key - (NSA) keys used to protect classified information. See Type 1 product. Type 2 key - (NSA) keys used to protect sensitive but unclassified (SBU) information. See Type 2 product. Vernam key - Type of key invented by Gilbert Vernam in 1918. See stream key.
A cryptographic key is called static if it is intended for use for a relatively long period of time and is typically intended for use in many instances of a cryptographic key establishment scheme. Contrast with an ephemeral key .
HC-256 is a stream cipher designed to provide bulk encryption in software at high speeds while permitting strong confidence in its security. [1] A 128-bit variant was submitted as an eSTREAM cipher candidate and has been selected as one of the four final contestants in the software profile. [2] [3]
The key is introduced in each round, usually in the form of "round keys" derived from it. (In some designs, the S-boxes themselves depend on the key.) Decryption is done by simply reversing the process (using the inverses of the S-boxes and P-boxes and applying the round keys in reversed order).
Picking any two ciphers, if the key used is the same for both, the second cipher could possibly undo the first cipher, partly or entirely. This is true of ciphers where the decryption process is exactly the same as the encryption process (a reciprocal cipher) – the second cipher would completely undo the first.
The running key cipher is a polyalphabetic substitution, the book cipher is a homophonic substitution. Perhaps the distinction is most clearly made by the fact that a running cipher would work best of all with a book of random numbers, whereas such a book (containing no text) would be useless for a book cipher.