org.spongycastle.crypto.macs

Class Poly1305

java.lang.Object

org.spongycastle.crypto.macs.Poly1305

All Implemented Interfaces:

Mac

public class Poly1305
extends java.lang.Object
implements Mac

Poly1305 message authentication code, designed by D. J. Bernstein.

Poly1305 computes a 128-bit (16 bytes) authenticator, using a 128 bit nonce and a 256 bit key consisting of a 128 bit key applied to an underlying cipher, and a 128 bit key (with 106 effective key bits) used in the authenticator.

The polynomial calculation in this implementation is adapted from the public domain poly1305-donna-unrolled C implementation by Andrew M (@floodyberry).

See Also:

Poly1305KeyGenerator

Constructor Summary

Constructors

Constructor and Description
Poly1305() Constructs a Poly1305 MAC, where the key passed to init() will be used directly.
Poly1305(BlockCipher cipher) Constructs a Poly1305 MAC, using a 128 bit block cipher.

Method Summary

Modifier and Type	Method and Description
int	doFinal(byte[] out, int outOff) Compute the final stage of the MAC writing the output to the out parameter.
java.lang.String	getAlgorithmName() Return the name of the algorithm the MAC implements.
int	getMacSize() Return the block size for this MAC (in bytes).
void	init(CipherParameters params) Initialises the Poly1305 MAC.
void	reset() Reset the MAC.
void	update(byte in) add a single byte to the mac for processing.
void	update(byte[] in, int inOff, int len)

Methods inherited from class java.lang.Object

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

Constructor Detail

Poly1305

public Poly1305()

Constructs a Poly1305 MAC, where the key passed to init() will be used directly.

Poly1305

public Poly1305(BlockCipher cipher)

Constructs a Poly1305 MAC, using a 128 bit block cipher.

Method Detail

init

public void init(CipherParameters params)
          throws java.lang.IllegalArgumentException

Initialises the Poly1305 MAC.

Specified by:

init in interface Mac

Parameters:

params - if used with a block cipher, then a ParametersWithIV containing a 128 bit nonce and a KeyParameter with a 256 bit key complying to the Poly1305 key format, otherwise just the KeyParameter.

Throws:

java.lang.IllegalArgumentException - if the params argument is inappropriate.

getAlgorithmName

public java.lang.String getAlgorithmName()

Description copied from interface: Mac

Return the name of the algorithm the MAC implements.

Specified by:

getAlgorithmName in interface Mac

Returns:

the name of the algorithm the MAC implements.

getMacSize

public int getMacSize()

Description copied from interface: Mac

Return the block size for this MAC (in bytes).

Specified by:

getMacSize in interface Mac

Returns:

the block size for this MAC in bytes.

update

public void update(byte in)
            throws java.lang.IllegalStateException

Description copied from interface: Mac

add a single byte to the mac for processing.

Specified by:

update in interface Mac

Parameters:

in - the byte to be processed.

Throws:

java.lang.IllegalStateException - if the MAC is not initialised.

update

public void update(byte[] in,
                   int inOff,
                   int len)
            throws DataLengthException,
                   java.lang.IllegalStateException

Specified by:

update in interface Mac

Parameters:

in - the array containing the input.

inOff - the index in the array the data begins at.

len - the length of the input starting at inOff.

Throws:

DataLengthException - if there isn't enough data in in.

java.lang.IllegalStateException - if the MAC is not initialised.

doFinal

public int doFinal(byte[] out,
                   int outOff)
            throws DataLengthException,
                   java.lang.IllegalStateException

Description copied from interface: Mac

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.

Specified by:

doFinal in interface Mac

Parameters:

out - the array the MAC is to be output to.

outOff - the offset into the out buffer the output is to start at.

Throws:

DataLengthException - if there isn't enough space in out.

java.lang.IllegalStateException - if the MAC is not initialised.

reset

public void reset()

Description copied from interface: Mac

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).

Specified by:

reset in interface Mac