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package org.spongycastle.crypto.macs;
import org.spongycastle.crypto.CipherParameters;
import org.spongycastle.crypto.DataLengthException;
import org.spongycastle.crypto.Mac;
import org.spongycastle.crypto.params.KeyParameter;
import org.spongycastle.crypto.util.Pack;
import org.spongycastle.util.Arrays;
/**
* Implementation of SipHash as specified in "SipHash: a fast short-input PRF", by Jean-Philippe
* Aumasson and Daniel J. Bernstein (https://131002.net/siphash/siphash.pdf).
* <p/>
* "SipHash is a family of PRFs SipHash-c-d where the integer parameters c and d are the number of
* compression rounds and the number of finalization rounds. A compression round is identical to a
* finalization round and this round function is called SipRound. Given a 128-bit key k and a
* (possibly empty) byte string m, SipHash-c-d returns a 64-bit value..."
*/
public class SipHash
implements Mac
{
protected final int c, d;
protected long k0, k1;
protected long v0, v1, v2, v3, v4;
protected byte[] buf = new byte[8];
protected int bufPos = 0;
protected int wordCount = 0;
/**
* SipHash-2-4
*/
public SipHash()
{
// use of this confuses flow analyser on earlier JDKs.
this.c = 2;
this.d = 4;
}
/**
* SipHash-c-d
*
* @param c the number of compression rounds
* @param d the number of finalization rounds
*/
public SipHash(int c, int d)
{
this.c = c;
this.d = d;
}
public String getAlgorithmName()
{
return "SipHash-" + c + "-" + d;
}
public int getMacSize()
{
return 8;
}
public void init(CipherParameters params)
throws IllegalArgumentException
{
if (!(params instanceof KeyParameter))
{
throw new IllegalArgumentException("'params' must be an instance of KeyParameter");
}
KeyParameter keyParameter = (KeyParameter)params;
byte[] key = keyParameter.getKey();
if (key.length != 16)
{
throw new IllegalArgumentException("'params' must be a 128-bit key");
}
this.k0 = Pack.littleEndianToLong(key, 0);
this.k1 = Pack.littleEndianToLong(key, 8);
reset();
}
public void update(byte input)
throws IllegalStateException
{
buf[bufPos] = input;
if (++bufPos == buf.length)
{
processMessageWord();
bufPos = 0;
}
}
public void update(byte[] input, int offset, int length)
throws DataLengthException,
IllegalStateException
{
for (int i = 0; i < length; ++i)
{
buf[bufPos] = input[offset + i];
if (++bufPos == buf.length)
{
processMessageWord();
bufPos = 0;
}
}
}
public long doFinal()
throws DataLengthException, IllegalStateException
{
buf[7] = (byte)(((wordCount << 3) + bufPos) & 0xff);
while (bufPos < 7)
{
buf[bufPos++] = 0;
}
processMessageWord();
v2 ^= 0xffL;
applySipRounds(d);
long result = v0 ^ v1 ^ v2 ^ v3;
reset();
return result;
}
public int doFinal(byte[] out, int outOff)
throws DataLengthException, IllegalStateException
{
long result = doFinal();
Pack.longToLittleEndian(result, out, outOff);
return 8;
}
public void reset()
{
v0 = k0 ^ 0x736f6d6570736575L;
v1 = k1 ^ 0x646f72616e646f6dL;
v2 = k0 ^ 0x6c7967656e657261L;
v3 = k1 ^ 0x7465646279746573L;
Arrays.fill(buf, (byte)0);
bufPos = 0;
wordCount = 0;
}
protected void processMessageWord()
{
++wordCount;
long m = Pack.littleEndianToLong(buf, 0);
v3 ^= m;
applySipRounds(c);
v0 ^= m;
}
protected void applySipRounds(int n)
{
for (int r = 0; r < n; ++r)
{
v0 += v1;
v2 += v3;
v1 = rotateLeft(v1, 13);
v3 = rotateLeft(v3, 16);
v1 ^= v0;
v3 ^= v2;
v0 = rotateLeft(v0, 32);
v2 += v1;
v0 += v3;
v1 = rotateLeft(v1, 17);
v3 = rotateLeft(v3, 21);
v1 ^= v2;
v3 ^= v0;
v2 = rotateLeft(v2, 32);
}
}
protected static long rotateLeft(long x, int n)
{
return (x << n) | (x >>> (64 - n));
}
}
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