Class SipHash

  • All Implemented Interfaces:
    Mac
    Direct Known Subclasses:
    SipHash128

    public class SipHash
    extends Object
    implements Mac
    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).

    "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..."

    • Field Detail

      • c

        protected final int c
      • d

        protected final int d
      • k0

        protected long k0
      • k1

        protected long k1
      • v0

        protected long v0
      • v1

        protected long v1
      • v2

        protected long v2
      • v3

        protected long v3
      • m

        protected long m
      • wordPos

        protected int wordPos
      • wordCount

        protected int wordCount
    • Constructor Detail

      • SipHash

        public SipHash()
        SipHash-2-4
      • SipHash

        public SipHash​(int c,
                       int d)
        SipHash-c-d
        Parameters:
        c - the number of compression rounds
        d - the number of finalization rounds
    • Method Detail

      • getAlgorithmName

        public String getAlgorithmName()
        Description copied from interface: Mac
        Return the name of the algorithm the MAC implements.
        Specified by:
        getAlgorithmName in interface Mac
        Returns:
        the name of the algorithm the MAC implements.
      • getMacSize

        public int getMacSize()
        Description copied from interface: Mac
        Return the block size for this MAC (in bytes).
        Specified by:
        getMacSize in interface Mac
        Returns:
        the block size for this MAC in bytes.
      • update

        public void update​(byte input)
                    throws IllegalStateException
        Description copied from interface: Mac
        add a single byte to the mac for processing.
        Specified by:
        update in interface Mac
        Parameters:
        input - the byte to be processed.
        Throws:
        IllegalStateException - if the MAC is not initialised.
      • doFinal

        public int doFinal​(byte[] out,
                           int outOff)
                    throws DataLengthException,
                           IllegalStateException
        Description copied from interface: Mac
        Compute the final stage of the MAC writing the output to the out parameter.

        doFinal leaves the MAC in the same state it was after the last init.

        Specified by:
        doFinal in interface Mac
        Parameters:
        out - the array the MAC is to be output to.
        outOff - the offset into the out buffer the output is to start at.
        Throws:
        DataLengthException - if there isn't enough space in out.
        IllegalStateException - if the MAC is not initialised.
      • reset

        public void reset()
        Description copied from interface: Mac
        Reset the MAC. At the end of resetting the MAC should be in the in the same state it was after the last init (if there was one).
        Specified by:
        reset in interface Mac
      • processMessageWord

        protected void processMessageWord()
      • applySipRounds

        protected void applySipRounds​(int n)
      • rotateLeft

        protected static long rotateLeft​(long x,
                                         int n)