public class OFB extends FeedbackMode
The full block size of the supplied cipher is used for the Output Feedback Mode. The bytes supplied are processed and returned immediately.
References:
sci.crypt FAQ, "Part 5: Product Ciphers,"
ftp://ftp.rtfm.mit.edu/pub/usenet/news.answers/cryptography-faq/part05
Copyright © 1997
Systemics Ltd on behalf of the
Cryptix Development Team.
All rights reserved.
$Revision: 1.6 $
currentByte, ivBlock, ivStart, lengthDECRYPT, ENCRYPT, UNINITIALIZED| Constructor and Description |
|---|
OFB()
Constructs an OFB cipher, assuming that the IV will be provided
via
setInitializationVector. |
OFB(Cipher cipher)
Constructs an OFB cipher, assuming that the IV will be provided
via
setInitializationVector. |
OFB(Cipher cipher,
byte[] iv)
Constructs a OFB cipher, using an initialization vector
provided in the constructor.
|
| Modifier and Type | Method and Description |
|---|---|
protected int |
engineBlockSize()
SPI: Returns the length of a block, in bytes.
|
protected void |
engineInitDecrypt(java.security.Key newkey)
SPI: Initializes this cipher for decryption, using the
specified key.
|
protected void |
engineInitEncrypt(java.security.Key newkey)
SPI: Initializes this cipher for encryption, using the
specified key.
|
protected int |
engineUpdate(byte[] in,
int inOffset,
int inLen,
byte[] out,
int outOffset)
SPI: This is the main engine method for updating data.
|
engineSetCipher, getInitializationVector, getInitializationVectorLength, setInitializationVectorengineGetParameter, engineSetParameter, getAlgorithms, getAlgorithms, getInstance, getInstance, toStringblockSize, clone, crypt, crypt, crypt, doFinal, doFinal, doFinal, doFinal, engineCiphertextBlockSize, engineCrypt, engineInBufferSize, engineOutBufferSize, enginePlaintextBlockSize, engineSetPaddingScheme, getAlgorithm, getCiphertextBlockSize, getInputBlockSize, getInstance, getMode, getOutputBlockSize, getPadding, getPaddingScheme, getParameter, getPlaintextBlockSize, getProvider, getState, inBufferSize, inBufferSizeFinal, initDecrypt, initEncrypt, isPaddingBlockCipher, outBufferSize, outBufferSizeFinal, setParameter, update, update, update, updatepublic OFB()
setInitializationVector.
The IV value must be unique during the lifetime of the key. If it is not unique, and an attacker has access to a different message encrypted under the same IV and key, all of the plaintext can normally be recovered.
public OFB(Cipher cipher)
setInitializationVector.
See the previous constructor for more details.cipher - the cipher object to use in OFB mode.java.lang.NullPointerException - if cipher == nullIllegalBlockSizeException - if cipher.getPlaintextBlockSize() !=
cipher.getCiphertextBlockSize()public OFB(Cipher cipher, byte[] iv)
The IV value must be unique during the lifetime of the key. If it is not unique, and an attacker has access to a different message encrypted under the same IV and key, all of the plaintext can normally be recovered.
cipher - the block cipher to useiv - the initial value for the shift register (IV)java.lang.NullPointerException - if cipher == nullprotected int engineBlockSize()
Cipher
The value may change when initEncrypt or
initDecrypt is called, but it should not change at
other times.
engineBlockSize in class Cipherprotected void engineInitEncrypt(java.security.Key newkey)
throws java.security.KeyException
CipherAfter a call to this method, the cipher's state is set to ENCRYPT.
engineInitEncrypt in class Ciphernewkey - the key to use for encryption.java.security.KeyException - if the key is invalid.protected void engineInitDecrypt(java.security.Key newkey)
throws java.security.KeyException
CipherAfter a call to this method, the cipher's state is set to DECRYPT.
engineInitDecrypt in class Ciphernewkey - the key to use for decryption.java.security.KeyException - if the key is invalid.protected int engineUpdate(byte[] in,
int inOffset,
int inLen,
byte[] out,
int outOffset)
in and out may be the same array, and the
input and output regions may overlap.
engineUpdate in class Cipherin - the input data.inOffset - the offset into in specifying where
the data starts.inLen - the length of the subarray.out - the output array.outOffset - the offset indicating where to start writing into
the out array.