gnu.javax.crypto.mode
Class CFB
- Cloneable, IBlockCipher, IMode
The cipher feedback mode. CFB mode is a stream mode that operates on
s
bit blocks, where 1 <=
s <=
b, if
b is the
underlying cipher's block size. Encryption is:
I[1] = IV
I[j] = LSB(b-s, I[j-1]) | C[j-1] for j = 2...n
O[j] = CIPH(K, I[j]) for j = 1,2...n
C[j] = P[j] ˆ MSB(s, O[j]) for j = 1,2...n
And decryption is:
I[1] = IV
I[j] = LSB(b-s, I[j-1]) | C[j-1] for j = 2...n
O[j] = CIPH(K, I[j]) for j = 1,2...n
P[j] = C[j] ˆ MSB(s, O[j]) for j = 1,2...n
CFB mode requires an initialization vector, which need not be kept secret.
References:
- Bruce Schneier, Applied Cryptography: Protocols, Algorithms, and
Source Code in C, Second Edition. (1996 John Wiley and Sons) ISBN
0-471-11709-9.
-
Recommendation for Block Cipher Modes of Operation Methods and Techniques,
Morris Dworkin.
Object | clone()- Returns a clone of this instance.
|
void | decryptBlock(byte[] in, int inOffset, byte[] out, int outOffset)- Decrypts exactly one block of ciphertext.
|
void | encryptBlock(byte[] in, int inOffset, byte[] out, int outOffset)- Encrypts exactly one block of plaintext.
|
void | setup()
|
void | teardown()
|
blockSizes, clone, currentBlockSize, decryptBlock, defaultBlockSize, defaultKeySize, encryptBlock, init, keySizes, name, reset, selfTest, setup, teardown, update |
clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait |
decryptBlock
public void decryptBlock(byte[] in,
int inOffset,
byte[] out,
int outOffset) Decrypts exactly one block of ciphertext.
- decryptBlock in interface IBlockCipher
- decryptBlock in interface BaseMode
in - the plaintext.inOffset - index of in from which to start considering
data.out - the ciphertext.outOffset - index of out from which to store result.
encryptBlock
public void encryptBlock(byte[] in,
int inOffset,
byte[] out,
int outOffset) Encrypts exactly one block of plaintext.
- encryptBlock in interface IBlockCipher
- encryptBlock in interface BaseMode
in - the plaintext.inOffset - index of in from which to start considering
data.out - the ciphertext.outOffset - index of out from which to store result.
CFB.java --
Copyright (C) 2002, 2006 Free Software Foundation, Inc.
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