Editing Residual block termination

{{Unreferenced|date=December 2009}}
In [[cryptography]], '''residual block termination''' is a variation of [[cipher block chaining]] mode (CBC) that does not require any [[Padding (cryptography)|padding]]. It does this by effectively changing to [[cipher feedback]] mode for one [[Block size (cryptography)|block]]. The cost is the increased complexity.

==Encryption procedure==
If the [[plaintext]] length ''N'' is not a multiple of the [[block size (cryptography)|block size]] ''L'':
*Encrypt the ⌊''N''/''L''⌋ full blocks of plaintext using the [[cipher block chaining]] [[block cipher modes of operation|mode]];
*Encrypt the last full encrypted block again;
*[[XOR]] the remaining bits of the plaintext with leftmost bits of the re-encrypted block.

==Decryption procedure==
*[[Decrypt]] the ⌊''N''/''L''⌋ full encrypted blocks using the Cipher Block Chaining mode;
*[[Encryption|Encrypt]] the last full encrypted block;
*[[XOR]] the remaining bits of the ciphertext with leftmost bits of the re-encrypted block.

==Short message==
For messages shorter than one block, residual block termination can use an encrypted [[initialization vector]] instead of the previously encrypted block.

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[[Category:Cryptographic algorithms]]


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