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The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 and up.

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package org.bouncycastle.crypto;


/**
 * The base interface for implementations of message authentication codes (MACs).
 */
public interface Mac
{
    /**
     * Initialise the MAC.
     *
     * @param params the key and other data required by the MAC.
     * @exception IllegalArgumentException if the params argument is
     * inappropriate.
     */
    public void init(CipherParameters params)
        throws IllegalArgumentException;

    /**
     * Return the name of the algorithm the MAC implements.
     *
     * @return the name of the algorithm the MAC implements.
     */
    public String getAlgorithmName();

    /**
     * Return the block size for this MAC (in bytes).
     *
     * @return the block size for this MAC in bytes.
     */
    public int getMacSize();

    /**
     * add a single byte to the mac for processing.
     *
     * @param in the byte to be processed.
     * @exception IllegalStateException if the MAC is not initialised.
     */
    public void update(byte in)
        throws IllegalStateException;

    /**
     * @param in the array containing the input.
     * @param inOff the index in the array the data begins at.
     * @param len the length of the input starting at inOff.
     * @exception IllegalStateException if the MAC is not initialised.
     * @exception DataLengthException if there isn't enough data in in.
     */
    public void update(byte[] in, int inOff, int len)
        throws DataLengthException, IllegalStateException;

    /**
     * Compute the final stage of the MAC writing the output to the out
     * parameter.
     * 
     * doFinal leaves the MAC in the same state it was after the last init.
     *
     * @param out the array the MAC is to be output to.
     * @param outOff the offset into the out buffer the output is to start at.
     * @exception DataLengthException if there isn't enough space in out.
     * @exception IllegalStateException if the MAC is not initialised.
     */
    public int doFinal(byte[] out, int outOff)
        throws DataLengthException, IllegalStateException;

    /**
     * Reset the MAC. At the end of resetting the MAC should be in the
     * in the same state it was after the last init (if there was one).
     */
    public void reset();
}