/**
* Process the <em>Clear</em> part of the message.
*
* @param in a byte array containing the <em>Clear</em> part of the message.
* @param offset the starting index in <code>in</code> where the <em>Clear</em> message bytes
* should be considered.
* @param length the count of bytes in <code>in</code>, starting from <code>offset</code> to
* consider.
* @throws IllegalStateException if no start-of-message method has been invoked earlier or the
* Integrity Protection service has not been activated.
*/
public void doClear(byte[] in, int offset, int length) {
if (!ready) {
throw new IllegalStateException();
}
if (!wantIntegrity) {
throw new IllegalStateException();
}
mac.update(in, offset, length);
}
/**
* Signals the end of the message transformation.
*
* @return the authentication tag bytes, if and when the Integrity Protection service was
* specified; otherwise a 0-long byte array is returned.
* @throws IllegalStateException if no start-of-message method has been invoked earlier.
*/
public byte[] endMessage() {
if (!ready) {
throw new IllegalStateException();
}
if (!wantIntegrity) {
return new byte[0];
}
byte[] result = mac.digest();
reset();
return result;
}
/**
* Signals the start of a new message to process with this <code>UST</code> with a designated
* <emIndex</em> value.
*
* @param ndx the <em>Index</em> to use with the new message.
* @throws LimitReachedException if the value of the <em>Index</em> has reached its allowed upper
* bound. To use this <code>UST</code> instance a new initialisation (with a new user-supplied
* key material) should occur.
* @throws InvalidKeyException if the underlying cipher, used in either or both the Integrity
* Protection and Confidentiality Protection functions has detected an exception.
*/
public void beginMessageWithIndex(BigInteger ndx)
throws LimitReachedException, InvalidKeyException {
if (ndx.compareTo(maxIndex) > 0) {
throw new LimitReachedException();
}
index = ndx;
// depending on the desired services, get keying material from the
// internal keystream generator and complete the relevant attributes.
// the key size shall be the same size as the user-supplied key material.
// remember we need the 1st generator if integrity is required even when
// confidentiality is not
if (wantConfidentiality || wantIntegrity) {
byte[] cpKey = new byte[keysize];
keystream.nextBytes(cpKey, 0, keysize);
cpAttributes.put(IBlockCipher.KEY_MATERIAL, cpKey);
if (cpStream instanceof ICMGenerator) {
cpAttributes.put(ICMGenerator.SEGMENT_INDEX, index);
} else {
cpAttributes.put(UMacGenerator.INDEX, new Integer(index.intValue()));
}
cpStream.init(cpAttributes);
}
if (wantIntegrity) {
byte[] ipKey = new byte[keysize];
keystream.nextBytes(ipKey, 0, keysize);
ipAttributes.put(IBlockCipher.KEY_MATERIAL, ipKey);
if (ipStream instanceof ICMGenerator) {
ipAttributes.put(ICMGenerator.SEGMENT_INDEX, index);
} else {
ipAttributes.put(UMacGenerator.INDEX, new Integer(index.intValue()));
}
ipStream.init(ipAttributes);
// get prefix bytes
byte[] prefix = new byte[macLength];
cpStream.nextBytes(prefix, 0, macLength);
macAttributes.put(TMMH16.PREFIX, prefix);
mac = new TMMH16();
macAttributes.put(TMMH16.KEYSTREAM, ipStream);
mac.init(macAttributes);
}
ready = true;
}
/**
* Process the <em>Opaque</em> part of the message.
*
* @param in a byte array containing the <em>Clear</em> part of the message.
* @param inOffset the starting index in <code>in</code> where the <em>Opaque</em> message bytes
* should be considered.
* @param length the count of bytes in <code>in</code>, starting from <code>inOffset</code> to
* consider.
* @param out the byte array where the enciphered opaque message should be stored.
* @param outOffset the starting offset in <code>out</code> where the enciphered bytes should be
* stored.
* @throws IllegalStateException if no start-of-message method has been invoked earlier.
* @throws LimitReachedException if one or both of the underlying keystream generators have
* reached their limit.
*/
public void doOpaque(byte[] in, int inOffset, int length, byte[] out, int outOffset)
throws LimitReachedException {
if (!ready) {
throw new IllegalStateException();
}
if (wantIntegrity) {
mac.update(in, inOffset, length);
}
if (wantConfidentiality) {
byte[] suffix = new byte[length];
cpStream.nextBytes(suffix, 0, length);
for (int i = 0; i < length; ) {
out[outOffset++] = (byte) (in[inOffset++] ^ suffix[i++]);
}
} else {
System.arraycopy(in, inOffset, out, outOffset, length);
}
}
/** Reset this instance and prepare for processing a new message. */
public void reset() {
ready = false;
if (wantIntegrity) {
mac.reset();
}
}