Example usage for java.math BigInteger modInverse

Introduction

In this page you can find the example usage for java.math BigInteger modInverse.

Prototype

public BigInteger modInverse(BigInteger m) 

Source Link

Document

Returns a BigInteger whose value is (this ^-1 mod m) .

Usage

From source file:Main.java

public static void main(String[] args) {

    BigInteger bi1 = new BigInteger("7");
    BigInteger bi2 = new BigInteger("20");

    // perform modInverse operation on bi1 using bi2
    BigInteger bi3 = bi1.modInverse(bi2);

    System.out.println(bi3);//www.  ja  va  2  s  . co m
}

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From source file:Main.java

public static BigInteger computeUnblindSignature(BigInteger r, BigInteger bs)
        throws UnsupportedEncodingException {
    RSAPublicKey pubKey = (RSAPublicKey) getPublicKey(public_key);
    BigInteger n = pubKey.getModulus();

    BigInteger s = r.modInverse(n).multiply(bs).mod(n);

    return s;//from  w  w  w  . j  a va  2s  .c  o m
}

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From source file:com.mastercard.mcbp.utils.crypto.CryptoServiceImpl.java

/**
 * {@inheritDoc}//  w w  w  .j a v  a  2  s . co m
 */
@Override
public final int initRsaPrivateKey(final ByteArray primeP, final ByteArray primeQ,
        final ByteArray primeExponentP, final ByteArray primeExponentQ, final ByteArray crtCoefficient)
        throws McbpCryptoException {
    try {
        final BigInteger p = new BigInteger(primeP.toHexString(), 16);
        final BigInteger q = new BigInteger(primeQ.toHexString(), 16);
        final BigInteger dp = new BigInteger(primeExponentP.toHexString(), 16);
        final BigInteger dq = new BigInteger(primeExponentQ.toHexString(), 16);
        final BigInteger a = new BigInteger(crtCoefficient.toHexString(), 16);

        final BigInteger n = p.multiply(q);
        final BigInteger e = dp.modInverse(p.subtract(BigInteger.ONE));

        final BigInteger d = e.modInverse(p.subtract(BigInteger.ONE).multiply(q.subtract(BigInteger.ONE))
                .divide((p.subtract(BigInteger.ONE)).gcd(q.subtract(BigInteger.ONE))));

        final RSAPrivateKey rsaKey = (RSAPrivateKey) KeyFactory.getInstance("RSA")
                .generatePrivate(new RSAPrivateCrtKeySpec(n, e, d, p, q, dp, dq, a));

        initRsaPrivate(rsaKey);

        return n.bitLength() / 8;

    } catch (final NoSuchAlgorithmException | InvalidKeySpecException e) {
        throw new McbpCryptoException(e.toString());
    }
}

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