iaik.security.md

Class Groestl256

java.lang.Object

java.security.MessageDigestSpi

java.security.MessageDigest

iaik.security.md.Groestl256

All Implemented Interfaces:

java.lang.Cloneable

public final class Groestl256
extends java.security.MessageDigest

This class implements the Groestl message digest algorithm.

A message digest algorithm represents the functionality of an one-way hash function for computing a fixed sized data value (message digest, hash) from input data of arbitrary size. The length of the resulting hash value usually is shorter than the length of the input data. Using a one-way hash function will make it easy to compute the hash from the given data, but hard to go the reverse way for calculating the input data when only the hash is known. Furthermore, a proper hash function should avoid any collision, meaning that it has to be hard to find two different messages producing the same hash value.

The Groestl-256 message digest algorithm produces a 256-bit hash-value of the given input data.

This class extends the java.security.MessageDigest class and applications should use one of the getInstance methods presented there to create a MessageDigest-Groestl object. Generally, an application wishing to compute the message digest of some data has to perform three steps:

• First an instance of the desired message digest algorithm has to be created using a proper getInstance method, e.g.:

   MessageDigest groestl = MessageDigest.getInstance("Groestl256");
   

• Second, the data to be hashed is supplied to the MessageDigest object just created by one or more calls to one of the update methods, e.g:
  

       groestl.update(m1);
       groestl.update(m2);
       ...
   

• Finally, the hash value can be computed using one of the digest methods:
  

   byte[] hash_value = groestl.digest();
   

There are several ways for combining update and digest methods for computing a message digest. Since this class implements the Cloneable interface, Groestl MessageDigest objects may be used for compute intermediate hashes through cloning (see http ://java.sun.com/products/JDK/1.2/docs/guide/security/CryptoSpec.html).

When the hash value successfully has been computed, the Groestl MessageDigest object automatically resets for being able to be supplied with new data to be hashed..

See Also:

MessageDigest

Constructor Summary

Constructors

Constructor and Description
Groestl256() Constructs a new instance.

Method Summary

Methods

Modifier and Type	Method and Description
java.lang.Object	clone()
protected void	doPadding()
protected void	engineCompress(byte[] input, int offset)
protected byte[]	engineDigest()
protected void	engineDigest(byte[] output, int offset)
protected int	engineDigest(byte[] buf, int offset, int len) Calculates the digest value and writes it to the given output buffer.
protected int	engineGetDigestLength()
protected void	engineReset()
protected void	engineUpdate(byte input)
protected void	engineUpdate(byte[] input, int offset, int len)

Methods inherited from class java.security.MessageDigest

digest, digest, digest, getAlgorithm, getDigestLength, getInstance, getInstance, getInstance, getProvider, isEqual, reset, toString, update, update, update, update

Methods inherited from class java.security.MessageDigestSpi

engineUpdate

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Groestl256

public Groestl256()

Constructs a new instance.

Method Detail

engineGetDigestLength

protected int engineGetDigestLength()

Overrides:

engineGetDigestLength in class java.security.MessageDigestSpi

engineCompress

protected void engineCompress(byte[] input,
                  int offset)

doPadding

protected void doPadding()

engineDigest

protected void engineDigest(byte[] output,
                int offset)

engineDigest

protected byte[] engineDigest()

Specified by:

engineDigest in class java.security.MessageDigestSpi

engineDigest

protected int engineDigest(byte[] buf,
               int offset,
               int len)
                    throws java.security.DigestException

Calculates the digest value and writes it to the given output buffer.

Overrides:

engineDigest in class java.security.MessageDigestSpi

Parameters:

buf - the output buffer in which to write the digest

offset - the start offset in the output buffer

len - the length of the digest value.

Returns:

the length of the digest written to the output buffer.

Throws:

java.security.DigestException - if an error occurs when calculating the digest value.

engineUpdate

protected void engineUpdate(byte input)

Specified by:

engineUpdate in class java.security.MessageDigestSpi

engineUpdate

protected void engineUpdate(byte[] input,
                int offset,
                int len)

Specified by:

engineUpdate in class java.security.MessageDigestSpi

engineReset

protected void engineReset()

Specified by:

engineReset in class java.security.MessageDigestSpi

clone

public java.lang.Object clone()
                       throws java.lang.CloneNotSupportedException

Overrides:

clone in class java.security.MessageDigest

Throws:

java.lang.CloneNotSupportedException