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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 JDK 1.4.
package org.bouncycastle.pqc.crypto.hqc;
class GF2PolynomialCalculator
{
private final int VEC_N_SIZE_64;
private final int PARAM_N;
private final long RED_MASK;
GF2PolynomialCalculator(int vec_n_size_64, int param_n, long red_mask)
{
VEC_N_SIZE_64 = vec_n_size_64;
PARAM_N = param_n;
RED_MASK = red_mask;
}
protected void multLongs(long[] res, long[] a, long[] b)
{
long[] stack = new long[VEC_N_SIZE_64 << 3];
long[] o_karat = new long[(VEC_N_SIZE_64 << 1) + 1];
karatsuba(o_karat, 0, a, 0, b, 0, VEC_N_SIZE_64, stack, 0);
reduce(res, o_karat);
}
private void base_mul(long[] c, int cOffset, long a, long b)
{
long h = 0;
long l = 0;
long g;
long[] u = new long[16];
long[] mask_tab = new long[4];
// Step 1
u[0] = 0;
u[1] = b & ((1L << (64 - 4)) - 1L);
u[2] = u[1] << 1;
u[3] = u[2] ^ u[1];
u[4] = u[2] << 1;
u[5] = u[4] ^ u[1];
u[6] = u[3] << 1;
u[7] = u[6] ^ u[1];
u[8] = u[4] << 1;
u[9] = u[8] ^ u[1];
u[10] = u[5] << 1;
u[11] = u[10] ^ u[1];
u[12] = u[6] << 1;
u[13] = u[12] ^ u[1];
u[14] = u[7] << 1;
u[15] = u[14] ^ u[1];
g=0;
long tmp1 = a & 15;
for(int i = 0; i < 16; i++)
{
long tmp2 = tmp1 - i;
g ^= (u[i] & -(1 - ((tmp2 | -tmp2) >>> 63)));
}
l = g;
h = 0;
// Step 2
for (byte i = 4; i < 64; i += 4)
{
g = 0;
long temp1 = (a >> i) & 15;
for (int j = 0; j < 16; ++j)
{
long tmp2 = temp1 - j;
g ^= (u[j] & -(1 - ((tmp2 | -tmp2) >>> 63)));
}
l ^= g << i;
h ^= g >>> (64 - i);
}
// Step 3
mask_tab [0] = - ((b >> 60) & 1);
mask_tab [1] = - ((b >> 61) & 1);
mask_tab [2] = - ((b >> 62) & 1);
mask_tab [3] = - ((b >> 63) & 1);
l ^= ((a << 60) & mask_tab[0]);
h ^= ((a >>> 4) & mask_tab[0]);
l ^= ((a << 61) & mask_tab[1]);
h ^= ((a >>> 3) & mask_tab[1]);
l ^= ((a << 62) & mask_tab[2]);
h ^= ((a >>> 2) & mask_tab[2]);
l ^= ((a << 63) & mask_tab[3]);
h ^= ((a >>> 1) & mask_tab[3]);
c[0 + cOffset] = l;
c[1 + cOffset] = h;
}
private void karatsuba_add1(long[] alh, int alhOffset,
long[] blh, int blhOffset,
long[] a, int aOffset,
long[] b, int bOffset,
int size_l, int size_h)
{
for (int i = 0; i < size_h; i++)
{
alh[i + alhOffset] = a[i+ aOffset] ^ a[i + size_l + aOffset];
blh[i + blhOffset] = b[i+ bOffset] ^ b[i + size_l + bOffset];
}
if (size_h < size_l)
{
alh[size_h + alhOffset] = a[size_h + aOffset];
blh[size_h + blhOffset] = b[size_h + bOffset];
}
}
private void karatsuba_add2(long[] o, int oOffset,
long[] tmp1, int tmp1Offset,
long[] tmp2, int tmp2Offset,
int size_l, int size_h)
{
for (int i = 0; i < (2 * size_l) ; i++)
{
tmp1[i + tmp1Offset] = tmp1[i + tmp1Offset] ^ o[i + oOffset];
}
for (int i = 0; i < ( 2 * size_h); i++)
{
tmp1[i + tmp1Offset] = tmp1[i + tmp1Offset] ^ tmp2[i + tmp2Offset];
}
for (int i = 0; i < (2 * size_l); i++)
{
o[i + size_l + oOffset] = o[i + size_l + oOffset] ^ tmp1[i + tmp1Offset];
}
}
/**
* Karatsuba multiplication of a and b, Implementation inspired from the NTL library.
*
* \param[out] o Polynomial
* \param[in] a Polynomial
* \param[in] b Polynomial
* \param[in] size Length of polynomial
* \param[in] stack Length of polynomial
*/
private void karatsuba(long[] o, int oOffset, long[] a, int aOffset, long[] b, int bOffset, int size, long[] stack, int stackOffset)
{
int size_l, size_h;
int ahOffset, bhOffset;
if (size == 1)
{
base_mul(o, oOffset, a[0 + aOffset], b[0 + bOffset]);
return;
}
size_h = size / 2;
size_l = (size + 1) / 2;
// alh = stack
int alhOffset = stackOffset;
// blh = stack with size_l offset
int blhOffset = alhOffset + size_l;
// tmp1 = stack with size_l * 2 offset;
int tmp1Offset = blhOffset + size_l;
// tmp2 = o with size_l * 2 offset;
int tmp2Offset = oOffset + size_l*2;
stackOffset += 4 * size_l;
ahOffset = aOffset + size_l;
bhOffset = bOffset + size_l;
karatsuba(o, oOffset, a, aOffset, b, bOffset, size_l, stack, stackOffset);
karatsuba(o, tmp2Offset, a, ahOffset, b, bhOffset, size_h, stack, stackOffset);
karatsuba_add1(stack, alhOffset, stack, blhOffset, a, aOffset, b, bOffset, size_l, size_h);
karatsuba(stack, tmp1Offset, stack, alhOffset, stack, blhOffset, size_l, stack, stackOffset);
karatsuba_add2(o, oOffset, stack, tmp1Offset, o, tmp2Offset, size_l, size_h);
}
/**
* @brief Compute o(x) = a(x) mod \f$ X^n - 1\f$
*
* This function computes the modular reduction of the polynomial a(x)
*
* @param[in] a Pointer to the polynomial a(x)
* @param[out] o Pointer to the result
*/
private void reduce(long[] o, long[] a)
{
int i;
long r;
long carry;
for (i = 0; i < VEC_N_SIZE_64; i++)
{
r = a[i + VEC_N_SIZE_64 - 1] >>> (PARAM_N & 0x3F);
carry = (long) (a[i + VEC_N_SIZE_64 ] << (64 - (PARAM_N & 0x3FL)));
o[i] = a[i] ^ r ^ carry;
}
o[VEC_N_SIZE_64 - 1] &= RED_MASK;
}
static void addLongs(long[] res, long[] a, long[] b)
{
for (int i = 0; i < a.length; i++)
{
res[i] = a[i] ^ b[i];
}
}
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