private void gHASHPartial(byte[] Y, byte[] b, int off, int len) {
GCMUtil.xor(Y, b, off, len);
multiplier.multiplyH(Y);
}
/**
* NOTE: MAC sizes from 32 bits to 128 bits (must be a multiple of 8) are supported. The default
* is 128 bits. Sizes less than 96 are not recommended, but are supported for specialized
* applications.
*/
@Override
public void init(boolean forEncryption, CipherParameters params) throws IllegalArgumentException {
this.forEncryption = forEncryption;
this.macBlock = null;
KeyParameter keyParam;
if (params instanceof AEADParameters) {
AEADParameters param = (AEADParameters) params;
nonce = param.getNonce();
initialAssociatedText = param.getAssociatedText();
int macSizeBits = param.getMacSize();
if (macSizeBits < 32 || macSizeBits > 128 || macSizeBits % 8 != 0) {
throw new IllegalArgumentException("Invalid value for MAC size: " + macSizeBits);
}
macSize = macSizeBits / 8;
keyParam = param.getKey();
} else if (params instanceof ParametersWithIV) {
ParametersWithIV param = (ParametersWithIV) params;
nonce = param.getIV();
initialAssociatedText = null;
macSize = 16;
keyParam = (KeyParameter) param.getParameters();
} else {
throw new IllegalArgumentException("invalid parameters passed to GCM");
}
int bufLength = forEncryption ? BLOCK_SIZE : (BLOCK_SIZE + macSize);
this.bufBlock = new byte[bufLength];
if (nonce == null || nonce.length < 1) {
throw new IllegalArgumentException("IV must be at least 1 byte");
}
// TODO Restrict macSize to 16 if nonce length not 12?
// Cipher always used in forward mode
// if keyParam is null we're reusing the last key.
if (keyParam != null) {
cipher.init(true, keyParam);
this.H = new byte[BLOCK_SIZE];
cipher.processBlock(H, 0, H, 0);
// GCMMultiplier tables don't change unless the key changes (and are expensive to init)
multiplier.init(H);
exp = null;
} else if (this.H == null) {
throw new IllegalArgumentException("Key must be specified in initial init");
}
this.J0 = new byte[BLOCK_SIZE];
if (nonce.length == 12) {
System.arraycopy(nonce, 0, J0, 0, nonce.length);
this.J0[BLOCK_SIZE - 1] = 0x01;
} else {
gHASH(J0, nonce, nonce.length);
byte[] X = new byte[BLOCK_SIZE];
Pack.longToBigEndian((long) nonce.length * 8, X, 8);
gHASHBlock(J0, X);
}
this.S = new byte[BLOCK_SIZE];
this.S_at = new byte[BLOCK_SIZE];
this.S_atPre = new byte[BLOCK_SIZE];
this.atBlock = new byte[BLOCK_SIZE];
this.atBlockPos = 0;
this.atLength = 0;
this.atLengthPre = 0;
this.counter = Arrays.clone(J0);
this.bufOff = 0;
this.totalLength = 0;
if (initialAssociatedText != null) {
processAADBytes(initialAssociatedText, 0, initialAssociatedText.length);
}
}
private void gHASHBlock(byte[] Y, byte[] b) {
GCMUtil.xor(Y, b);
multiplier.multiplyH(Y);
}