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Class cryptix.provider.mode.CFB
java.lang.Object
|
+----java.security.IJCE_Traceable
|
+----java.security.Cipher
|
+----java.security.Mode
|
+----cryptix.provider.mode.FeedbackMode
|
+----cryptix.provider.mode.CFB
- public class CFB
- extends FeedbackMode
Implements a byte-oriented stream cipher using n-bit CFB with an
n-bit-sized block cipher.
The full block size of the supplied cipher is used for the
Cipher Feedback Mode. The bytes supplied are processed and
returned immediately.
References:
- Bruce Schneier,
"Section 9.6 Cipher 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 © 1995-1997
Systemics Ltd on behalf of the
Cryptix Development Team.
All rights reserved.
$Revision: 1.4 $
- Author:
- David Hopwood, Raif S. Naffah
-
CFB()
- Constructs a CFB mode object.
-
CFB(Cipher)
- Constructs a CFB cipher, assuming that the IV will be provided
via
setInitializationVector
.
-
CFB(Cipher, byte[])
- Constructs a CFB 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.
-
engineSetCipher(Cipher)
- SPI: Sets the underlying cipher.
-
engineUpdate(byte[], int, int, byte[], int)
- SPI: This is the main engine method for updating data.
-
next_block()
- Rotates the IV left by currentByte bytes, to mimic the V2.2
behaviour.
CFB
public CFB()
- Constructs a CFB mode object.
The IV is provided via setInitializationVector
. This IV
must be unique during the lifetime of the key. If it is not
unique, at least the first block of the plaintext can be recovered.
CFB
public CFB(Cipher cipher)
- Constructs a CFB 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 CFB mode.
- Throws: NullPointerException
- if cipher == null
CFB
public CFB(Cipher cipher,
byte iv[])
- Constructs a CFB cipher, using an initialization vector
provided in the constructor.
- Parameters:
- cipher - the block cipher to use
- iv - the initial value for the shift register (IV)
- Throws: NullPointerException
- if cipher == null
engineSetCipher
protected void engineSetCipher(Cipher cipher)
- SPI: Sets the underlying cipher.
- Overrides:
- engineSetCipher in class FeedbackMode
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
next_block
protected void next_block()
- Rotates the IV left by currentByte bytes, to mimic the V2.2
behaviour. This is needed in order to implement the variant of CFB
used by PGP.
- See Also:
- CFB_PGP
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