package org.bouncycastle.crypto.engines;

import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.InvalidCipherTextException;
import org.bouncycastle.crypto.Wrapper;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;
import org.bouncycastle.crypto.params.ParametersWithRandom;
import org.bouncycastle.util.Arrays;

an implementation of the AES Key Wrapper from the NIST Key Wrap Specification as described in RFC 3394.

For further details see: http://www.ietf.org/rfc/rfc3394.txt and http://csrc.nist.gov/encryption/kms/key-wrap.pdf.

/** * an implementation of the AES Key Wrapper from the NIST Key Wrap * Specification as described in RFC 3394. * <p> * For further details see: <a href="http://www.ietf.org/rfc/rfc3394.txt">http://www.ietf.org/rfc/rfc3394.txt</a> * and <a href="http://csrc.nist.gov/encryption/kms/key-wrap.pdf">http://csrc.nist.gov/encryption/kms/key-wrap.pdf</a>. */
public class RFC3394WrapEngine implements Wrapper { private BlockCipher engine; private KeyParameter param; private boolean forWrapping; private byte[] iv = { (byte)0xa6, (byte)0xa6, (byte)0xa6, (byte)0xa6, (byte)0xa6, (byte)0xa6, (byte)0xa6, (byte)0xa6 }; public RFC3394WrapEngine(BlockCipher engine) { this.engine = engine; } public void init( boolean forWrapping, CipherParameters param) { this.forWrapping = forWrapping; if (param instanceof ParametersWithRandom) { param = ((ParametersWithRandom) param).getParameters(); } if (param instanceof KeyParameter) { this.param = (KeyParameter)param; } else if (param instanceof ParametersWithIV) { this.iv = ((ParametersWithIV)param).getIV(); this.param = (KeyParameter)((ParametersWithIV) param).getParameters(); if (this.iv.length != 8) { throw new IllegalArgumentException("IV not equal to 8"); } } } public String getAlgorithmName() { return engine.getAlgorithmName(); } public byte[] wrap( byte[] in, int inOff, int inLen) { if (!forWrapping) { throw new IllegalStateException("not set for wrapping"); } int n = inLen / 8; if ((n * 8) != inLen) { throw new DataLengthException("wrap data must be a multiple of 8 bytes"); } byte[] block = new byte[inLen + iv.length]; byte[] buf = new byte[8 + iv.length]; System.arraycopy(iv, 0, block, 0, iv.length); System.arraycopy(in, 0, block, iv.length, inLen); engine.init(true, param); for (int j = 0; j != 6; j++) { for (int i = 1; i <= n; i++) { System.arraycopy(block, 0, buf, 0, iv.length); System.arraycopy(block, 8 * i, buf, iv.length, 8); engine.processBlock(buf, 0, buf, 0); int t = n * j + i; for (int k = 1; t != 0; k++) { byte v = (byte)t; buf[iv.length - k] ^= v; t >>>= 8; } System.arraycopy(buf, 0, block, 0, 8); System.arraycopy(buf, 8, block, 8 * i, 8); } } return block; } public byte[] unwrap( byte[] in, int inOff, int inLen) throws InvalidCipherTextException { if (forWrapping) { throw new IllegalStateException("not set for unwrapping"); } int n = inLen / 8; if ((n * 8) != inLen) { throw new InvalidCipherTextException("unwrap data must be a multiple of 8 bytes"); } byte[] block = new byte[inLen - iv.length]; byte[] a = new byte[iv.length]; byte[] buf = new byte[8 + iv.length]; System.arraycopy(in, 0, a, 0, iv.length); System.arraycopy(in, iv.length, block, 0, inLen - iv.length); engine.init(false, param); n = n - 1; for (int j = 5; j >= 0; j--) { for (int i = n; i >= 1; i--) { System.arraycopy(a, 0, buf, 0, iv.length); System.arraycopy(block, 8 * (i - 1), buf, iv.length, 8); int t = n * j + i; for (int k = 1; t != 0; k++) { byte v = (byte)t; buf[iv.length - k] ^= v; t >>>= 8; } engine.processBlock(buf, 0, buf, 0); System.arraycopy(buf, 0, a, 0, 8); System.arraycopy(buf, 8, block, 8 * (i - 1), 8); } } if (!Arrays.constantTimeAreEqual(a, iv)) { throw new InvalidCipherTextException("checksum failed"); } return block; } }