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java.lang.Object | +--xjava.security.IJCE_Traceable | +--xjava.security.Cipher | +--xjava.security.Mode | +--cryptix.provider.mode.FeedbackMode | +--cryptix.provider.mode.OFB
Implements a byte-oriented stream cipher using n-bit OFB with an n-bit-sized block cipher.
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 $
Fields inherited from class cryptix.provider.mode.FeedbackMode |
currentByte,
ivBlock,
ivStart,
length |
Fields inherited from class xjava.security.Mode |
cipher |
Fields inherited from class xjava.security.Cipher |
DECRYPT,
ENCRYPT,
UNINITIALIZED |
Constructor Summary | |
OFB()
Constructs an OFB cipher, assuming that the IV will be provided via setInitializationVector . |
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OFB(Cipher cipher)
Constructs an OFB cipher, assuming that the IV will be provided via setInitializationVector . |
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OFB(Cipher cipher,
byte[] iv)
Constructs a OFB cipher, using an initialization vector provided in the constructor. |
Method Summary | |
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. |
Methods inherited from class cryptix.provider.mode.FeedbackMode |
engineSetCipher,
getInitializationVector,
getInitializationVectorLength,
setInitializationVector |
Methods inherited from class xjava.security.Mode |
engineGetParameter,
engineSetParameter,
getAlgorithms,
getAlgorithms,
getInstance,
getInstance,
toString |
Methods inherited from class java.lang.Object |
equals,
finalize,
getClass,
hashCode,
notify,
notifyAll,
wait,
wait,
wait |
Constructor Detail |
public 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.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)Method Detail |
protected int engineBlockSize()
The value may change when initEncrypt
or
initDecrypt
is called, but it should not change at
other times.
protected void engineInitEncrypt(java.security.Key newkey) throws java.security.KeyException
After a call to this method, the cipher's state is set to ENCRYPT.
key
- the key to use for encryption.protected void engineInitDecrypt(java.security.Key newkey) throws java.security.KeyException
After a call to this method, the cipher's state is set to DECRYPT.
key
- the key to use for decryption.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.
in
- 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.
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Cryptix V3.2 | |||||||||
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