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In cryptography, a block cipher is a deterministic algorithm that operates on fixed-length groups of bits, called blocks. Block ciphers are the elementary building blocks of many cryptographic protocols. They are ubiquitous in the storage and exchange of data, where such data is secured and authenticated via encryption.
The propagating cipher block chaining [25] or plaintext cipher-block chaining [26] mode was designed to cause small changes in the ciphertext to propagate indefinitely when decrypting, as well as when encrypting. In PCBC mode, each block of plaintext is XORed with both the previous plaintext block and the previous ciphertext block before being ...
Ciphertext stealing is a technique for encrypting plaintext using a block cipher, without padding the message to a multiple of the block size, so the ciphertext is the same size as the plaintext. It does this by altering processing of the last two blocks of the message.
Block ciphers operate on a fixed length string of bits. The length of this bit string is the block size . [ 1 ] Both the input ( plaintext ) and output ( ciphertext ) are the same length; the output cannot be shorter than the input – this follows logically from the pigeonhole principle and the fact that the cipher must be reversible – and ...
CCM mode (counter with cipher block chaining message authentication code; counter with CBC-MAC) is a mode of operation for cryptographic block ciphers. It is an authenticated encryption algorithm designed to provide both authentication and confidentiality. CCM mode is only defined for block ciphers with a block length of 128 bits. [1] [2]
Ciphers, on the other hand, work at a lower level: the level of individual letters, small groups of letters, or, in modern schemes, individual bits and blocks of bits. Some systems used both codes and ciphers in one system, using superencipherment to increase the security.
In cryptography, RC5 is a symmetric-key block cipher notable for its simplicity. Designed by Ronald Rivest in 1994, [2] RC stands for "Rivest Cipher", or alternatively, "Ron's Code" (compare RC2 and RC4). The Advanced Encryption Standard (AES) candidate RC6 was based on RC5.
In cryptography, a cipher block chaining message authentication code (CBC-MAC) is a technique for constructing a message authentication code (MAC) from a block cipher.The message is encrypted with some block cipher algorithm in cipher block chaining (CBC) mode to create a chain of blocks such that each block depends on the proper encryption of the previous block.