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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. Note: this package includes the NTRU encryption algorithms.

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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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