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Diffstat (limited to 'core/src/main/java/org/spongycastle/pqc/crypto/ntru/NTRUEncryptionKeyPairGenerator.java')
| -rw-r--r-- | core/src/main/java/org/spongycastle/pqc/crypto/ntru/NTRUEncryptionKeyPairGenerator.java | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/pqc/crypto/ntru/NTRUEncryptionKeyPairGenerator.java b/core/src/main/java/org/spongycastle/pqc/crypto/ntru/NTRUEncryptionKeyPairGenerator.java new file mode 100644 index 00000000..fd483f09 --- /dev/null +++ b/core/src/main/java/org/spongycastle/pqc/crypto/ntru/NTRUEncryptionKeyPairGenerator.java @@ -0,0 +1,113 @@ +package org.spongycastle.pqc.crypto.ntru; + +import org.spongycastle.crypto.AsymmetricCipherKeyPair; +import org.spongycastle.crypto.AsymmetricCipherKeyPairGenerator; +import org.spongycastle.crypto.KeyGenerationParameters; +import org.spongycastle.pqc.math.ntru.polynomial.DenseTernaryPolynomial; +import org.spongycastle.pqc.math.ntru.polynomial.IntegerPolynomial; +import org.spongycastle.pqc.math.ntru.polynomial.Polynomial; +import org.spongycastle.pqc.math.ntru.polynomial.ProductFormPolynomial; +import org.spongycastle.pqc.math.ntru.util.Util; + +/** + * Generates key pairs.<br> + * 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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