gnu.crypto.pad
Class TBC
java.lang.Object
|
+--gnu.crypto.pad.BasePad
|
+--gnu.crypto.pad.TBC
- All Implemented Interfaces:
- IPad
- public final class TBC
- extends BasePad
The implementation of the Trailing Bit Complement (TBC) padding algorithm.
In this mode, "...the data string is padded at the trailing end with the
complement of the trailing bit of the unpadded message: if the trailing bit
is 1, then 0 bits are appended, and if the trailing bit is
0, then 1 bits are appended. As few bits are added as are
necessary to meet the formatting size requirement."
References:
Recommendation for Block Cipher Modes of Operation Methods and Techniques,
Morris Dworkin.
- Version:
- $Revision: 1.3 $
Constructor Summary |
(package private) |
TBC()
Trivial package-private constructor for use by the Factory class. |
Method Summary |
byte[] |
pad(byte[] in,
int offset,
int length)
Returns the byte sequence that should be appended to the designated input. |
void |
setup()
|
int |
unpad(byte[] in,
int offset,
int length)
Returns the number of bytes to discard from a designated input buffer. |
Methods inherited from class java.lang.Object |
, clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
TBC
TBC()
- Trivial package-private constructor for use by the Factory class.
- See Also:
PadFactory
setup
public void setup()
- Overrides:
setup
in class BasePad
pad
public byte[] pad(byte[] in,
int offset,
int length)
- Description copied from interface:
IPad
- Returns the byte sequence that should be appended to the designated input.
- Overrides:
pad
in class BasePad
- Following copied from interface:
gnu.crypto.pad.IPad
- Parameters:
in
- the input buffer containing the bytes to pad.offset
- the starting index of meaningful data in in.length
- the number of meaningful bytes in in.- Returns:
- the possibly 0-byte long sequence to be appended to the designated
input.
unpad
public int unpad(byte[] in,
int offset,
int length)
throws WrongPaddingException
- Description copied from interface:
IPad
- Returns the number of bytes to discard from a designated input buffer.
- Overrides:
unpad
in class BasePad
- Following copied from interface:
gnu.crypto.pad.IPad
- Parameters:
in
- the input buffer containing the bytes to unpad.offset
- the starting index of meaningful data in in.length
- the number of meaningful bytes in in.- Returns:
- the number of bytes to discard, to the left of index position
offset + length in in. In other words, if the return
value of a successful invocation of this method is result, then
the unpadded byte sequence will be offset + length - result bytes
in in, starting from index position offset.
- Throws:
WrongPaddingException
- if the data is not terminated with the
expected padding bytes.
Copyright ©2001-2002
Free Software Foundation, Inc.. All Rights Reserved.