org.bouncycastle.pqc.crypto.bike.BIKEUtils Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of bcprov-ext-debug-jdk18on Show documentation

The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for Java 1.8 and later with debug enabled.

The newest version!

package org.bouncycastle.pqc.crypto.bike;

import org.bouncycastle.crypto.Xof;
import org.bouncycastle.util.Pack;

class BIKEUtils
{
    static int getHammingWeight(byte[] bytes)
    {
        int hammingWeight = 0;
        for (int i = 0; i < bytes.length; i++)
        {
            hammingWeight += bytes[i];
        }
        return hammingWeight;
    }

    static void fromBitArrayToByteArray(byte[] out, byte[] in, int inOff, int inLen)
    {
        int count = 0;
        int pos = 0;
        long len = inLen;
        while (count < len)
        {
            if (count + 8 >= inLen)
            {// last set of bits cannot have enough 8 bits
                int b = in[inOff + count];
                for (int j = inLen - count - 1; j >= 1; j--)
                { //bin in reversed order
                    b |= in[inOff + count + j] << j;
                }
                out[pos] = (byte)b;
            }
            else
            {
                int b = in[inOff + count];
                for (int j = 7; j >= 1; j--)
                { //bin in reversed order
                    b |= in[inOff + count + j] << j;
                }
                out[pos] = (byte)b;
            }

            count += 8;
            pos++;
        }
    }

    static void generateRandomByteArray(byte[] res, int size, int weight, Xof digest)
    {
        byte[] buf = new byte[4];
        int rand_pos;

        for (int i = weight - 1; i >= 0; i--)
        {
            digest.doOutput(buf, 0, 4);
            long temp = ((long)Pack.littleEndianToInt(buf, 0)) & 0xFFFFFFFFL;
            temp = temp * (size - i) >> 32;
            rand_pos = (int) temp;

            rand_pos += i;

            if(CHECK_BIT(res, rand_pos) != 0)
            {
                rand_pos = i;
            }
            SET_BIT(res, rand_pos);
        }
    }
    protected static int CHECK_BIT(byte[] tmp, int position)
    {
        int index = position / 8;
        int pos = position % 8;
        return ((tmp[index] >>> (pos))  & 0x01);
    }
    protected static void SET_BIT(byte[] tmp, int position)
    {
        int index = position/8;
        int pos = position%8;
        tmp[index] |= (long)(1L << (long)(pos));
    }
}