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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.crypto.rainbow;

import java.security.SecureRandom;

import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.params.ParametersWithRandom;
import org.bouncycastle.pqc.crypto.MessageSigner;
import org.bouncycastle.pqc.crypto.rainbow.util.ComputeInField;
import org.bouncycastle.pqc.crypto.rainbow.util.GF2Field;

/**
 * It implements the sign and verify functions for the Rainbow Signature Scheme.
 * Here the message, which has to be signed, is updated. The use of
 * different hash functions is possible.
 * 

* Detailed information about the signature and the verify-method is to be found * in the paper of Jintai Ding, Dieter Schmidt: Rainbow, a New Multivariable * Polynomial Signature Scheme. ACNS 2005: 164-175 * (http://dx.doi.org/10.1007/11496137_12) */ public class RainbowSigner implements MessageSigner { // Source of randomness private SecureRandom random; // The length of a document that can be signed with the privKey int signableDocumentLength; // Container for the oil and vinegar variables of all the layers private short[] x; private ComputeInField cf = new ComputeInField(); RainbowKeyParameters key; public void init(boolean forSigning, CipherParameters param) { if (forSigning) { if (param instanceof ParametersWithRandom) { ParametersWithRandom rParam = (ParametersWithRandom)param; this.random = rParam.getRandom(); this.key = (RainbowPrivateKeyParameters)rParam.getParameters(); } else { this.random = new SecureRandom(); this.key = (RainbowPrivateKeyParameters)param; } } else { this.key = (RainbowPublicKeyParameters)param; } this.signableDocumentLength = this.key.getDocLength(); } /** * initial operations before solving the Linear equation system. * * @param layer the current layer for which a LES is to be solved. * @param msg the message that should be signed. * @return Y_ the modified document needed for solving LES, (Y_ = * A1^{-1}*(Y-b1)) linear map L1 = A1 x + b1. */ private short[] initSign(Layer[] layer, short[] msg) { /* preparation: Modifies the document with the inverse of L1 */ // tmp = Y - b1: short[] tmpVec = new short[msg.length]; tmpVec = cf.addVect(((RainbowPrivateKeyParameters)this.key).getB1(), msg); // Y_ = A1^{-1} * (Y - b1) : short[] Y_ = cf.multiplyMatrix(((RainbowPrivateKeyParameters)this.key).getInvA1(), tmpVec); /* generates the vinegar vars of the first layer at random */ for (int i = 0; i < layer[0].getVi(); i++) { x[i] = (short)random.nextInt(); x[i] = (short)(x[i] & GF2Field.MASK); } return Y_; } /** * This function signs the message that has been updated, making use of the * private key. *

* For computing the signature, L1 and L2 are needed, as well as LES should * be solved for each layer in order to find the Oil-variables in the layer. *

* The Vinegar-variables of the first layer are random generated. * * @param message the message * @return the signature of the message. */ public byte[] generateSignature(byte[] message) { Layer[] layer = ((RainbowPrivateKeyParameters)this.key).getLayers(); int numberOfLayers = layer.length; x = new short[((RainbowPrivateKeyParameters)this.key).getInvA2().length]; // all variables short[] Y_; // modified document short[] y_i; // part of Y_ each polynomial int counter; // index of the current part of the doc short[] solVec; // the solution of LES pro layer short[] tmpVec; // the signature as an array of shorts: short[] signature; // the signature as a byte-array: byte[] S = new byte[layer[numberOfLayers - 1].getViNext()]; short[] msgHashVals = makeMessageRepresentative(message); // shows if an exception is caught boolean ok; do { ok = true; counter = 0; try { Y_ = initSign(layer, msgHashVals); for (int i = 0; i < numberOfLayers; i++) { y_i = new short[layer[i].getOi()]; solVec = new short[layer[i].getOi()]; // solution of LES /* copy oi elements of Y_ into y_i */ for (int k = 0; k < layer[i].getOi(); k++) { y_i[k] = Y_[counter]; counter++; // current index of Y_ } /* * plug in the vars of the previous layer in order to get * the vars of the current layer */ solVec = cf.solveEquation(layer[i].plugInVinegars(x), y_i); if (solVec == null) { // LES is not solveable throw new Exception("LES is not solveable!"); } /* copy the new vars into the x-array */ for (int j = 0; j < solVec.length; j++) { x[layer[i].getVi() + j] = solVec[j]; } } /* apply the inverse of L2: (signature = A2^{-1}*(b2+x)) */ tmpVec = cf.addVect(((RainbowPrivateKeyParameters)this.key).getB2(), x); signature = cf.multiplyMatrix(((RainbowPrivateKeyParameters)this.key).getInvA2(), tmpVec); /* cast signature from short[] to byte[] */ for (int i = 0; i < S.length; i++) { S[i] = ((byte)signature[i]); } } catch (Exception se) { // if one of the LESs was not solveable - sign again ok = false; } } while (!ok); /* return the signature in bytes */ return S; } /** * This function verifies the signature of the message that has been * updated, with the aid of the public key. * * @param message the message * @param signature the signature of the message * @return true if the signature has been verified, false otherwise. */ public boolean verifySignature(byte[] message, byte[] signature) { short[] sigInt = new short[signature.length]; short tmp; for (int i = 0; i < signature.length; i++) { tmp = (short)signature[i]; tmp &= (short)0xff; sigInt[i] = tmp; } short[] msgHashVal = makeMessageRepresentative(message); // verify short[] verificationResult = verifySignatureIntern(sigInt); // compare boolean verified = true; if (msgHashVal.length != verificationResult.length) { return false; } for (int i = 0; i < msgHashVal.length; i++) { verified = verified && msgHashVal[i] == verificationResult[i]; } return verified; } /** * Signature verification using public key * * @param signature vector of dimension n * @return document hash of length n - v1 */ private short[] verifySignatureIntern(short[] signature) { short[][] coeff_quadratic = ((RainbowPublicKeyParameters)this.key).getCoeffQuadratic(); short[][] coeff_singular = ((RainbowPublicKeyParameters)this.key).getCoeffSingular(); short[] coeff_scalar = ((RainbowPublicKeyParameters)this.key).getCoeffScalar(); short[] rslt = new short[coeff_quadratic.length];// n - v1 int n = coeff_singular[0].length; int offset = 0; // array position short tmp = 0; // for scalar for (int p = 0; p < coeff_quadratic.length; p++) { // no of polynomials offset = 0; for (int x = 0; x < n; x++) { // calculate quadratic terms for (int y = x; y < n; y++) { tmp = GF2Field.multElem(coeff_quadratic[p][offset], GF2Field.multElem(signature[x], signature[y])); rslt[p] = GF2Field.addElem(rslt[p], tmp); offset++; } // calculate singular terms tmp = GF2Field.multElem(coeff_singular[p][x], signature[x]); rslt[p] = GF2Field.addElem(rslt[p], tmp); } // add scalar rslt[p] = GF2Field.addElem(rslt[p], coeff_scalar[p]); } return rslt; } /** * This function creates the representative of the message which gets signed * or verified. * * @param message the message * @return message representative */ private short[] makeMessageRepresentative(byte[] message) { // the message representative short[] output = new short[this.signableDocumentLength]; int h = 0; int i = 0; do { if (i >= message.length) { break; } output[i] = (short)message[h]; output[i] &= (short)0xff; h++; i++; } while (i < output.length); return output; } }





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