Difference between revisions 4237102 and 6096439 on simplewiki

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In modern [[cryptography]], [[Symmetric-key algorithm|symmetric key]] [[cipher]]s are generally divided into [[stream cipher]]s and [[block cipher]]s. [[Block cipher]]s operate on a fixed length string of [[bit]]s. The length of this bit string is the '''block size'''. Both the input ([[plaintext]]) and output ([[ciphertext]]) are the same length; the output cannot be shorter than the input – this is logically required by the [[Pigeonhole principle]] and the fact that the cipher must be invertible – and it is simply undesirable for the output to be longer than the input.

The [[Data Encryption Standard|DES]] is using a block size of 64 bits (8 [[byte]]s) while the [[Advanced Encryption Standard|AES]] is using a block size of 128 bits (16 bytes). '''[[Rijndael key schedule|Rijndael]]''', supports block sizes of 128, 192, and 256 bits, although the extra block sizes were not adopted by the [[Advanced Encryption Standard|AES]] standard.

A few block ciphers, such as [[RC5]], support a variable block size. The [[Luby-Rackoff]] [[construction]] and the [[Richard Outerbridge|Outerbridge]] [[construction]] can both increase the effective block size of a [[cipher]]. 

Few [[cipher]]s have unusual block sizes, for example the [[3-Way|3-Way block cipher]] have an unusual block size of 96 bits (12 [[byte]]s).


{{Math-stub}}

[[Category:Cryptography]]