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/*
 * (C) Copyright IBM Corp. 2013
 */

package com.sun.crypto.provider;

import java.security.ProviderException;

import jdk.internal.HotSpotIntrinsicCandidate;

This class represents the GHASH function defined in NIST 800-38D under section 6.4. It needs to be constructed w/ a hash subkey, i.e. block H. Given input of 128-bit blocks, it will process and output a 128-bit block.

This function is used in the implementation of GCM mode.

Since:1.8
/** * This class represents the GHASH function defined in NIST 800-38D * under section 6.4. It needs to be constructed w/ a hash subkey, i.e. * block H. Given input of 128-bit blocks, it will process and output * a 128-bit block. * * <p>This function is used in the implementation of GCM mode. * * @since 1.8 */
final class GHASH { private static long getLong(byte[] buffer, int offset) { long result = 0; int end = offset + 8; for (int i = offset; i < end; ++i) { result = (result << 8) + (buffer[i] & 0xFF); } return result; } private static void putLong(byte[] buffer, int offset, long value) { int end = offset + 8; for (int i = end - 1; i >= offset; --i) { buffer[i] = (byte) value; value >>= 8; } } private static final int AES_BLOCK_SIZE = 16; // Multiplies state[0], state[1] by subkeyH[0], subkeyH[1]. private static void blockMult(long[] st, long[] subH) { long Z0 = 0; long Z1 = 0; long V0 = subH[0]; long V1 = subH[1]; long X; // Separate loops for processing state[0] and state[1]. X = st[0]; for (int i = 0; i < 64; i++) { // Zi+1 = Zi if bit i of x is 0 long mask = X >> 63; Z0 ^= V0 & mask; Z1 ^= V1 & mask; // Save mask for conditional reduction below. mask = (V1 << 63) >> 63; // V = rightshift(V) long carry = V0 & 1; V0 = V0 >>> 1; V1 = (V1 >>> 1) | (carry << 63); // Conditional reduction modulo P128. V0 ^= 0xe100000000000000L & mask; X <<= 1; } X = st[1]; for (int i = 64; i < 127; i++) { // Zi+1 = Zi if bit i of x is 0 long mask = X >> 63; Z0 ^= V0 & mask; Z1 ^= V1 & mask; // Save mask for conditional reduction below. mask = (V1 << 63) >> 63; // V = rightshift(V) long carry = V0 & 1; V0 = V0 >>> 1; V1 = (V1 >>> 1) | (carry << 63); // Conditional reduction. V0 ^= 0xe100000000000000L & mask; X <<= 1; } // calculate Z128 long mask = X >> 63; Z0 ^= V0 & mask; Z1 ^= V1 & mask; // Save result. st[0] = Z0; st[1] = Z1; } /* subkeyH and state are stored in long[] for GHASH intrinsic use */ // hash subkey H; should not change after the object has been constructed private final long[] subkeyH; // buffer for storing hash private final long[] state; // variables for save/restore calls private long stateSave0, stateSave1;
Initializes the cipher in the specified mode with the given key and iv.
Params:
  • subkeyH – the hash subkey
Throws:
/** * Initializes the cipher in the specified mode with the given key * and iv. * * @param subkeyH the hash subkey * * @exception ProviderException if the given key is inappropriate for * initializing this digest */
GHASH(byte[] subkeyH) throws ProviderException { if ((subkeyH == null) || subkeyH.length != AES_BLOCK_SIZE) { throw new ProviderException("Internal error"); } state = new long[2]; this.subkeyH = new long[2]; this.subkeyH[0] = getLong(subkeyH, 0); this.subkeyH[1] = getLong(subkeyH, 8); }
Resets the GHASH object to its original state, i.e. blank w/ the same subkey H. Used after digest() is called and to re-use this object for different data w/ the same H.
/** * Resets the GHASH object to its original state, i.e. blank w/ * the same subkey H. Used after digest() is called and to re-use * this object for different data w/ the same H. */
void reset() { state[0] = 0; state[1] = 0; }
Save the current snapshot of this GHASH object.
/** * Save the current snapshot of this GHASH object. */
void save() { stateSave0 = state[0]; stateSave1 = state[1]; }
Restores this object using the saved snapshot.
/** * Restores this object using the saved snapshot. */
void restore() { state[0] = stateSave0; state[1] = stateSave1; } private static void processBlock(byte[] data, int ofs, long[] st, long[] subH) { st[0] ^= getLong(data, ofs); st[1] ^= getLong(data, ofs + 8); blockMult(st, subH); } void update(byte[] in) { update(in, 0, in.length); } void update(byte[] in, int inOfs, int inLen) { if (inLen == 0) { return; } ghashRangeCheck(in, inOfs, inLen, state, subkeyH); processBlocks(in, inOfs, inLen/AES_BLOCK_SIZE, state, subkeyH); } private static void ghashRangeCheck(byte[] in, int inOfs, int inLen, long[] st, long[] subH) { if (inLen < 0) { throw new RuntimeException("invalid input length: " + inLen); } if (inOfs < 0) { throw new RuntimeException("invalid offset: " + inOfs); } if (inLen > in.length - inOfs) { throw new RuntimeException("input length out of bound: " + inLen + " > " + (in.length - inOfs)); } if (inLen % AES_BLOCK_SIZE != 0) { throw new RuntimeException("input length/block size mismatch: " + inLen); } // These two checks are for C2 checking if (st.length != 2) { throw new RuntimeException("internal state has invalid length: " + st.length); } if (subH.length != 2) { throw new RuntimeException("internal subkeyH has invalid length: " + subH.length); } } /* * This is an intrinsified method. The method's argument list must match * the hotspot signature. This method and methods called by it, cannot * throw exceptions or allocate arrays as it will breaking intrinsics */ @HotSpotIntrinsicCandidate private static void processBlocks(byte[] data, int inOfs, int blocks, long[] st, long[] subH) { int offset = inOfs; while (blocks > 0) { processBlock(data, offset, st, subH); blocks--; offset += AES_BLOCK_SIZE; } } byte[] digest() { byte[] result = new byte[AES_BLOCK_SIZE]; putLong(result, 0, state[0]); putLong(result, 8, state[1]); reset(); return result; } }