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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 1.5 to JDK 1.8 with debug enabled.
package org.bouncycastle.pqc.math.ntru.polynomial;
import org.bouncycastle.util.Arrays;
/**
* A polynomial class that combines five coefficients into one long
value for
* faster multiplication by a ternary polynomial.
* Coefficients can be between 0 and 2047 and are stored in bits 0..11, 12..23, ..., 48..59 of a long
number.
*/
public class LongPolynomial5
{
private long[] coeffs; // groups of 5 coefficients
private int numCoeffs;
/**
* Constructs a LongPolynomial5
from a IntegerPolynomial
. The two polynomials are independent of each other.
*
* @param p the original polynomial. Coefficients must be between 0 and 2047.
*/
public LongPolynomial5(IntegerPolynomial p)
{
numCoeffs = p.coeffs.length;
coeffs = new long[(numCoeffs + 4) / 5];
int cIdx = 0;
int shift = 0;
for (int i = 0; i < numCoeffs; i++)
{
coeffs[cIdx] |= ((long)p.coeffs[i]) << shift;
shift += 12;
if (shift >= 60)
{
shift = 0;
cIdx++;
}
}
}
private LongPolynomial5(long[] coeffs, int numCoeffs)
{
this.coeffs = coeffs;
this.numCoeffs = numCoeffs;
}
/**
* Multiplies the polynomial with a TernaryPolynomial
, taking the indices mod N and the values mod 2048.
*/
public LongPolynomial5 mult(TernaryPolynomial poly2)
{
long[][] prod = new long[5][coeffs.length + (poly2.size() + 4) / 5 - 1]; // intermediate results, the subarrays are shifted by 0,...,4 coefficients
// multiply ones
int[] ones = poly2.getOnes();
for (int idx = 0; idx != ones.length; idx++)
{
int pIdx = ones[idx];
int cIdx = pIdx / 5;
int m = pIdx - cIdx * 5; // m = pIdx % 5
for (int i = 0; i < coeffs.length; i++)
{
prod[m][cIdx] = (prod[m][cIdx] + coeffs[i]) & 0x7FF7FF7FF7FF7FFL;
cIdx++;
}
}
// multiply negative ones
int[] negOnes = poly2.getNegOnes();
for (int idx = 0; idx != negOnes.length; idx++)
{
int pIdx = negOnes[idx];
int cIdx = pIdx / 5;
int m = pIdx - cIdx * 5; // m = pIdx % 5
for (int i = 0; i < coeffs.length; i++)
{
prod[m][cIdx] = (0x800800800800800L + prod[m][cIdx] - coeffs[i]) & 0x7FF7FF7FF7FF7FFL;
cIdx++;
}
}
// combine shifted coefficients (5 arrays) into a single array of length prod[*].length+1
long[] cCoeffs = Arrays.copyOf(prod[0], prod[0].length + 1);
for (int m = 1; m <= 4; m++)
{
int shift = m * 12;
int shift60 = 60 - shift;
long mask = (1L << shift60) - 1;
int pLen = prod[m].length;
for (int i = 0; i < pLen; i++)
{
long upper, lower;
upper = prod[m][i] >> shift60;
lower = prod[m][i] & mask;
cCoeffs[i] = (cCoeffs[i] + (lower << shift)) & 0x7FF7FF7FF7FF7FFL;
int nextIdx = i + 1;
cCoeffs[nextIdx] = (cCoeffs[nextIdx] + upper) & 0x7FF7FF7FF7FF7FFL;
}
}
// reduce indices of cCoeffs modulo numCoeffs
int shift = 12 * (numCoeffs % 5);
for (int cIdx = coeffs.length - 1; cIdx < cCoeffs.length; cIdx++)
{
long iCoeff; // coefficient to shift into the [0..numCoeffs-1] range
int newIdx;
if (cIdx == coeffs.length - 1)
{
iCoeff = numCoeffs == 5 ? 0 : cCoeffs[cIdx] >> shift;
newIdx = 0;
}
else
{
iCoeff = cCoeffs[cIdx];
newIdx = cIdx * 5 - numCoeffs;
}
int base = newIdx / 5;
int m = newIdx - base * 5; // m = newIdx % 5
long lower = iCoeff << (12 * m);
long upper = iCoeff >> (12 * (5 - m));
cCoeffs[base] = (cCoeffs[base] + lower) & 0x7FF7FF7FF7FF7FFL;
int base1 = base + 1;
if (base1 < coeffs.length)
{
cCoeffs[base1] = (cCoeffs[base1] + upper) & 0x7FF7FF7FF7FF7FFL;
}
}
return new LongPolynomial5(cCoeffs, numCoeffs);
}
public IntegerPolynomial toIntegerPolynomial()
{
int[] intCoeffs = new int[numCoeffs];
int cIdx = 0;
int shift = 0;
for (int i = 0; i < numCoeffs; i++)
{
intCoeffs[i] = (int)((coeffs[cIdx] >> shift) & 2047);
shift += 12;
if (shift >= 60)
{
shift = 0;
cIdx++;
}
}
return new IntegerPolynomial(intCoeffs);
}
}
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