Example usage for org.bouncycastle.math.ec ECCurve.Fp getB

Introduction

In this page you can find the example usage for org.bouncycastle.math.ec ECCurve.Fp getB.

Prototype

public ECFieldElement getB() 

Source Link

Usage

From source file:eu.betaas.taas.securitymanager.common.mqv.ECMQVUtils.java

License:Apache License

/**
 * A method to perform embedded public key validation (BC style)
 * @param pub: the public key to be validated
 * @return true if valid/*from   w ww  .  j  av a2s .  co m*/
 */
public static boolean validateEmbedPubKey(AsymmetricKeyParameter pub) {

    ECPublicKeyParameters ecPub = (ECPublicKeyParameters) pub;
    ECCurve.Fp fpCurve = (Fp) ecPub.getParameters().getCurve();
    BigInteger p = fpCurve.getQ();
    BigInteger xq = ecPub.getQ().normalize().getXCoord().toBigInteger();
    BigInteger yq = ecPub.getQ().normalize().getYCoord().toBigInteger();

    // validate the xq and yq, they must be in the interval [0,q-1]
    if (xq.compareTo(BigInteger.ZERO) == -1 && xq.compareTo(p.subtract(BigInteger.ONE)) == 1
            && yq.compareTo(BigInteger.ZERO) == -1 && yq.compareTo(p.subtract(BigInteger.ONE)) == 1)
        return false;

    BigInteger a = fpCurve.getA().toBigInteger();
    BigInteger b = fpCurve.getB().toBigInteger();

    // test whether Q lies in the curve defined by y^2(mod p)=x^3+ax+b (mod p)
    BigInteger rightEq = xq.pow(3).add(a.multiply(xq)).add(b).mod(p);
    //      System.out.println("x^3+ax+b    = "+rightEq.toString());

    BigInteger y2 = yq.pow(2).mod(p);
    //      System.out.println("y^2       = "+y2.toString());

    if (y2.compareTo(rightEq) != 0)
        return false;

    return true;
}

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