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Class cryptix.provider.mode.OFB
java.lang.Object
|
+----java.security.IJCE_Traceable
|
+----java.security.Cipher
|
+----java.security.Mode
|
+----cryptix.provider.mode.FeedbackMode
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+----cryptix.provider.mode.OFB
- public class OFB
- extends FeedbackMode
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:
- Bruce Schneier,
"Section 9.8 Output Feedback Mode," and "Section 9.11 Choosing a Cipher Mode,"
Applied Cryptography, 2nd edition,
John Wiley & Sons, 1996
-
sci.crypt
FAQ, "Part 5: Product Ciphers,"
ftp://ftp.rtfm.mit.edu/pub/usenet/news.answers/cryptography-faq/part05
- National Bureau of Standards (now NIST),
"DES Modes of Operation,"
NBS FIPS PUB 81,
U.S. Department of Commerce, December 1980
Copyright © 1997
Systemics Ltd on behalf of the
Cryptix Development Team.
All rights reserved.
$Revision: 1.5 $
- Author:
- David Hopwood, Raif S. Naffah
-
OFB()
- Constructs an OFB cipher, assuming that the IV will be provided
via
setInitializationVector
.
-
OFB(Cipher)
- Constructs an OFB cipher, assuming that the IV will be provided
via
setInitializationVector
.
-
OFB(Cipher, byte[])
- Constructs a OFB cipher, using an initialization vector
provided in the constructor.
-
engineBlockSize()
- SPI: Returns the length of a block, in bytes.
-
engineInitDecrypt(Key)
- SPI: Initializes this cipher for decryption, using the
specified key.
-
engineInitEncrypt(Key)
- SPI: Initializes this cipher for encryption, using the
specified key.
-
engineUpdate(byte[], int, int, byte[], int)
- SPI: This is the main engine method for updating data.
OFB
public OFB()
- Constructs an OFB cipher, assuming that the IV will be provided
via
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.
OFB
public OFB(Cipher cipher)
- Constructs an OFB cipher, assuming that the IV will be provided
via
setInitializationVector
.
See the previous constructor for more details.
- Parameters:
- cipher - the cipher object to use in OFB mode.
- Throws: NullPointerException
- if cipher == null
- Throws: IllegalBlockSizeException
- if cipher.getPlaintextBlockSize() !=
cipher.getCiphertextBlockSize()
OFB
public OFB(Cipher cipher,
byte iv[])
- Constructs a OFB cipher, using an initialization vector
provided in the constructor.
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.
- Parameters:
- cipher - the block cipher to use
- iv - the initial value for the shift register (IV)
- Throws: NullPointerException
- if cipher == null
engineBlockSize
protected int engineBlockSize()
- SPI: Returns the length of a block, in bytes.
- Overrides:
- engineBlockSize in class Cipher
engineInitEncrypt
protected void engineInitEncrypt(Key newkey) throws KeyException
- SPI: Initializes this cipher for encryption, using the
specified key.
- Overrides:
- engineInitEncrypt in class Cipher
engineInitDecrypt
protected void engineInitDecrypt(Key newkey) throws KeyException
- SPI: Initializes this cipher for decryption, using the
specified key.
- Overrides:
- engineInitDecrypt in class Cipher
engineUpdate
protected int engineUpdate(byte in[],
int inOffset,
int inLen,
byte out[],
int outOffset)
- SPI: This is the main engine method for updating data.
It may be called with any size of input.
in
and out
may be the same array, and the
input and output regions may overlap.
- Parameters:
- 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.
- Returns:
- the number of bytes written.
- Overrides:
- engineUpdate in class Cipher
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