gnu.crypto.mac
Class TMMH16
- Cloneable, IMac
public class TMMH16
implements Cloneable
TMMH is a
universal hash function suitable for message
authentication in the Wegman-Carter paradigm, as in the Stream Cipher
Security Transform. It is simple, quick, and especially appropriate for
Digital Signal Processors and other processors with a fast multiply
operation, though a straightforward implementation requires storage equal in
length to the largest message to be hashed.
TMMH is a simple hash function which maps a key and a message to a
hash value. There are two versions of TMMH: TMMH/16 and TMMH/32.
TMMH
can be used as a message authentication code, as described in Section 5 (see
References).
The key, message, and hash value are all octet strings, and the lengths of
these quantities are denoted as
KEY_LENGTH
,
MESSAGE_LENGTH
, and
TAG_LENGTH
, respectively. The
values of
KEY_LENGTH
and
TAG_LENGTH
MUST be fixed for any particular fixed value of the key, and
must obey the alignment restrictions described below.
The parameter
MAX_HASH_LENGTH
, which denotes the maximum
value which
MESSAGE_LENGTH
may take, is equal to
KEY_LENGTH - TAG_LENGTH
.
References:
-
The Truncated Multi-Modular Hash Function (TMMH), David A. McGrew.
TMMH16() - Trivial 0-arguments constructor.
|
byte[] | digest() - Completes the MAC by performing final operations such as
padding and resetting the instance.
|
byte[] | digest(IRandom prng) - Similar to the same method with no arguments, but uses the designated
random number generator to compute needed keying material.
|
void | init(Map attributes) - Initialises the algorithm with designated attributes.
|
int | macSize() - Returns the output length in bytes of this MAC algorithm.
|
void | reset() - Resets the algorithm instance for re-initialisation and use with other
characteristics.
|
boolean | selfTest() - A basic test.
|
void | update(byte b) - Continues a MAC operation using the input byte.
|
void | update(byte b, IRandom prng) - Similar to the same method with one argument, but uses the designated
random number generator to compute needed keying material.
|
void | update(byte[] b, int offset, int len) - Continues a MAC operation, by filling the buffer, processing
data in the algorithm's MAC_SIZE-bit block(s), updating the context and
count, and buffering the remaining bytes in buffer for the next
operation.
|
void | update(byte[] b, int offset, int len, IRandom prng) - Similar to the same method with three arguments, but uses the
designated random number generator to compute needed keying material.
|
KEYSTREAM
public static final String KEYSTREAM
PREFIX
public static final String PREFIX
TAG_LENGTH
public static final String TAG_LENGTH
TMMH16
public TMMH16()
Trivial 0-arguments constructor.
digest
public byte[] digest()
Completes the MAC by performing final operations such as
padding and resetting the instance.
- digest in interface IMac
- digest in interface BaseMac
- the array of bytes representing the MAC value.
digest
public byte[] digest(IRandom prng)
Similar to the same method with no arguments, but uses the designated
random number generator to compute needed keying material.
prng
- the source of randomness to use.
- the final result of the algorithm.
init
public void init(Map attributes)
throws InvalidKeyException,
IllegalStateException
Initialises the algorithm with designated attributes. Permissible names
and values are described in the class documentation above.
- init in interface IMac
- init in interface BaseMac
attributes
- a set of name-value pairs that describe the desired
future instance behaviour.
macSize
public int macSize()
Returns the output length in bytes of this MAC algorithm.
- macSize in interface IMac
- macSize in interface BaseMac
- the output length in bytes of this MAC algorithm.
reset
public void reset()
Resets the algorithm instance for re-initialisation and use with other
characteristics. This method always succeeds.
- reset in interface IMac
- reset in interface BaseMac
selfTest
public boolean selfTest()
A basic test. Ensures that the MAC of a pre-determined message is equal
to a known pre-computed value.
- selfTest in interface IMac
- selfTest in interface BaseMac
true
if the implementation passes a basic self-test.
Returns false
otherwise.
update
public void update(byte b)
Continues a MAC operation using the input byte.
- update in interface IMac
- update in interface BaseMac
b
- the input byte to digest.
update
public void update(byte b,
IRandom prng)
Similar to the same method with one argument, but uses the designated
random number generator to compute needed keying material.
b
- the byte to process.prng
- the source of randomness to use.
update
public void update(byte[] b,
int offset,
int len)
Continues a MAC operation, by filling the buffer, processing
data in the algorithm's MAC_SIZE-bit block(s), updating the context and
count, and buffering the remaining bytes in buffer for the next
operation.
- update in interface IMac
- update in interface BaseMac
offset
- start of meaningful bytes in input block.
update
public void update(byte[] b,
int offset,
int len,
IRandom prng)
Similar to the same method with three arguments, but uses the
designated random number generator to compute needed keying material.
b
- the byte array to process.offset
- the starting offset in b
to start considering
the bytes to process.len
- the number of bytes in b
starting from
offset
to process.prng
- the source of randomness to use.
Copyright © 2001, 2002, 2003
Free Software Foundation,
Inc. All Rights Reserved.