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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 and up.

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package org.bouncycastle.pqc.crypto.ntru;

import org.bouncycastle.crypto.AsymmetricCipherKeyPair;
import org.bouncycastle.crypto.AsymmetricCipherKeyPairGenerator;
import org.bouncycastle.crypto.KeyGenerationParameters;
import org.bouncycastle.pqc.math.ntru.polynomial.DenseTernaryPolynomial;
import org.bouncycastle.pqc.math.ntru.polynomial.IntegerPolynomial;
import org.bouncycastle.pqc.math.ntru.polynomial.Polynomial;
import org.bouncycastle.pqc.math.ntru.polynomial.ProductFormPolynomial;
import org.bouncycastle.pqc.math.ntru.util.Util;

/**
 * Generates key pairs.
* The parameter p is hardcoded to 3. */ public class NTRUEncryptionKeyPairGenerator implements AsymmetricCipherKeyPairGenerator { private NTRUEncryptionKeyGenerationParameters params; /** * Constructs a new instance with a set of encryption parameters. * * @param param encryption parameters */ public void init(KeyGenerationParameters param) { this.params = (NTRUEncryptionKeyGenerationParameters)param; } /** * Generates a new encryption key pair. * * @return a key pair */ public AsymmetricCipherKeyPair generateKeyPair() { int N = params.N; int q = params.q; int df = params.df; int df1 = params.df1; int df2 = params.df2; int df3 = params.df3; int dg = params.dg; boolean fastFp = params.fastFp; boolean sparse = params.sparse; Polynomial t; IntegerPolynomial fq; IntegerPolynomial fp = null; // choose a random f that is invertible mod 3 and q while (true) { IntegerPolynomial f; // choose random t, calculate f and fp if (fastFp) { // if fastFp=true, f is always invertible mod 3 t = params.polyType == NTRUParameters.TERNARY_POLYNOMIAL_TYPE_SIMPLE ? Util.generateRandomTernary(N, df, df, sparse, params.getRandom()) : ProductFormPolynomial.generateRandom(N, df1, df2, df3, df3, params.getRandom()); f = t.toIntegerPolynomial(); f.mult(3); f.coeffs[0] += 1; } else { t = params.polyType == NTRUParameters.TERNARY_POLYNOMIAL_TYPE_SIMPLE ? Util.generateRandomTernary(N, df, df - 1, sparse, params.getRandom()) : ProductFormPolynomial.generateRandom(N, df1, df2, df3, df3 - 1, params.getRandom()); f = t.toIntegerPolynomial(); fp = f.invertF3(); if (fp == null) { continue; } } fq = f.invertFq(q); if (fq == null) { continue; } break; } // if fastFp=true, fp=1 if (fastFp) { fp = new IntegerPolynomial(N); fp.coeffs[0] = 1; } // choose a random g that is invertible mod q DenseTernaryPolynomial g; while (true) { g = DenseTernaryPolynomial.generateRandom(N, dg, dg - 1, params.getRandom()); if (g.invertFq(q) != null) { break; } } IntegerPolynomial h = g.mult(fq, q); h.mult3(q); h.ensurePositive(q); g.clear(); fq.clear(); NTRUEncryptionPrivateKeyParameters priv = new NTRUEncryptionPrivateKeyParameters(h, t, fp, params.getEncryptionParameters()); NTRUEncryptionPublicKeyParameters pub = new NTRUEncryptionPublicKeyParameters(h, params.getEncryptionParameters()); return new AsymmetricCipherKeyPair(pub, priv); } }




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