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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 to JDK 1.8. Note: this package includes the NTRU encryption algorithms.

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package org.bouncycastle.crypto.macs;

import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.InvalidCipherTextException;
import org.bouncycastle.crypto.Mac;
import org.bouncycastle.crypto.modes.GCMBlockCipher;
import org.bouncycastle.crypto.params.AEADParameters;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;

/**
 * The GMAC specialisation of Galois/Counter mode (GCM) detailed in NIST Special Publication
 * 800-38D.
 * 

* GMac is an invocation of the GCM mode where no data is encrypted (i.e. all input data to the Mac * is processed as additional authenticated data with the underlying GCM block cipher). */ public class GMac implements Mac { private final GCMBlockCipher cipher; private final int macSizeBits; /** * Creates a GMAC based on the operation of a block cipher in GCM mode. *

* This will produce an authentication code the length of the block size of the cipher. * * @param cipher * the cipher to be used in GCM mode to generate the MAC. */ public GMac(final GCMBlockCipher cipher) { // use of this confused flow analyser in some earlier JDKs this.cipher = cipher; this.macSizeBits = 128; } /** * Creates a GMAC based on the operation of a 128 bit block cipher in GCM mode. * * @param macSizeBits * the mac size to generate, in bits. Must be a multiple of 8 and >= 32 and <= 128. * Sizes less than 96 are not recommended, but are supported for specialized applications. * @param cipher * the cipher to be used in GCM mode to generate the MAC. */ public GMac(final GCMBlockCipher cipher, final int macSizeBits) { this.cipher = cipher; this.macSizeBits = macSizeBits; } /** * Initialises the GMAC - requires a {@link ParametersWithIV} providing a {@link KeyParameter} * and a nonce. */ public void init(final CipherParameters params) throws IllegalArgumentException { if (params instanceof ParametersWithIV) { final ParametersWithIV param = (ParametersWithIV)params; final byte[] iv = param.getIV(); final KeyParameter keyParam = (KeyParameter)param.getParameters(); // GCM is always operated in encrypt mode to calculate MAC cipher.init(true, new AEADParameters(keyParam, macSizeBits, iv)); } else { throw new IllegalArgumentException("GMAC requires ParametersWithIV"); } } public String getAlgorithmName() { return cipher.getUnderlyingCipher().getAlgorithmName() + "-GMAC"; } public int getMacSize() { return macSizeBits / 8; } public void update(byte in) throws IllegalStateException { cipher.processAADByte(in); } public void update(byte[] in, int inOff, int len) throws DataLengthException, IllegalStateException { cipher.processAADBytes(in, inOff, len); } public int doFinal(byte[] out, int outOff) throws DataLengthException, IllegalStateException { try { return cipher.doFinal(out, outOff); } catch (InvalidCipherTextException e) { // Impossible in encrypt mode throw new IllegalStateException(e.toString()); } } public void reset() { cipher.reset(); } }





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