Example usage for java.math BigInteger remainder

Introduction

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

Prototype

public BigInteger remainder(BigInteger val) 

Source Link

Document

Returns a BigInteger whose value is (this % val) .

Usage

From source file:Main.java

public static void main(String[] args) {

    BigInteger bi1 = new BigInteger("-100");
    BigInteger bi2 = new BigInteger("3");

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

    System.out.println(bi3);//from w  w  w  . j a  v  a  2 s . c o m
}

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From source file:Main.java

public static boolean isDivisible(BigInteger a, BigInteger b) {
    return a.remainder(b).compareTo(ZERO) == 0;
}

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From source file:net.ripe.ipresource.IpRange.java

private boolean canBeDividedByThePowerOfTwo(BigInteger number, int power) {
    return number.remainder(BigInteger.valueOf(2).pow(power)).equals(BigInteger.ZERO);
}

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From source file:piuk.blockchain.android.util.WalletUtils.java

public static String formatValue(final BigInteger value, final String plusSign, final String minusSign) {
    final boolean negative = value.compareTo(BigInteger.ZERO) < 0;
    final BigInteger absValue = value.abs();

    final String sign = negative ? minusSign : plusSign;

    final int coins = absValue.divide(Utils.COIN).intValue();
    final int cents = absValue.remainder(Utils.COIN).intValue();

    if (cents % 1000000 == 0)
        return String.format("%s%d.%02d", sign, coins, cents / 1000000);
    else if (cents % 10000 == 0)
        return String.format("%s%d.%04d", sign, coins, cents / 10000);
    else//  w  w w  .  j a va 2 s .  com
        return String.format("%s%d.%08d", sign, coins, cents);
}

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From source file:test.be.fedict.eid.applet.RSATest.java

@Test
public void testManualEncryption() throws Exception {
    while (true) {
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA",
                BouncyCastleProvider.PROVIDER_NAME);
        SecureRandom random = new SecureRandom();
        int keySize = 128;
        keyPairGenerator.initialize(new RSAKeyGenParameterSpec(keySize, RSAKeyGenParameterSpec.F0), random);
        KeyPair keyPair = keyPairGenerator.generateKeyPair();
        PrivateKey privateKey = keyPair.getPrivate();
        PublicKey publicKey = keyPair.getPublic();
        RSAPrivateCrtKey rsaPrivateKey = (RSAPrivateCrtKey) privateKey;
        LOG.debug("private key modulus: " + rsaPrivateKey.getModulus());
        RSAPublicKey rsaPublicKey = (RSAPublicKey) publicKey;
        LOG.debug("public key modulus: " + rsaPublicKey.getModulus());
        LOG.debug("public key exponent: " + rsaPublicKey.getPublicExponent());
        LOG.debug("modulus size: " + rsaPublicKey.getModulus().toByteArray().length);

        Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
        cipher.init(Cipher.ENCRYPT_MODE, privateKey);

        int dataSize = keySize / 8 - 11;
        byte[] data1 = new byte[dataSize];
        for (int i = 0; i < data1.length; i++) {
            data1[i] = 0x00;/*from   ww  w .ja  v a 2s .  c o  m*/
        }
        byte[] data2 = new byte[dataSize];
        for (int i = 0; i < data2.length; i++) {
            data2[i] = 0x00;
        }
        data2[data2.length - 1] = 0x07;

        byte[] signatureValue1 = cipher.doFinal(data1);

        LOG.debug("signature size: " + signatureValue1.length);

        cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
        cipher.init(Cipher.ENCRYPT_MODE, privateKey);
        byte[] signatureValue2 = cipher.doFinal(data2);

        BigInteger sigBigInt1 = new BigInteger(signatureValue1);
        BigInteger sigBigInt2 = new BigInteger(signatureValue2);
        BigInteger msgBigInt1 = sigBigInt1.modPow(rsaPublicKey.getPublicExponent(), rsaPublicKey.getModulus());
        BigInteger msgBigInt2 = sigBigInt2.modPow(rsaPublicKey.getPublicExponent(), rsaPublicKey.getModulus());
        LOG.debug("msg big int: " + msgBigInt1);
        byte[] msgBytes1 = msgBigInt1.toByteArray();
        LOG.debug("original message size: " + msgBytes1.length);
        LOG.debug("original message1: " + new String(Hex.encodeHex(msgBytes1)));
        LOG.debug("original message2: " + new String(Hex.encodeHex(msgBigInt2.toByteArray())));

        LOG.debug("msg1 prime: " + msgBigInt1.isProbablePrime(100));
        LOG.debug("msg2 prime: " + msgBigInt2.isProbablePrime(100));

        // BigInteger.pow offers a very naive implementation
        LOG.debug("calculating s1^e...");
        BigInteger s1_e = sigBigInt1.pow(rsaPublicKey.getPublicExponent().intValue());
        LOG.debug("s1^e: " + s1_e);
        LOG.debug("calculating s2^e...");
        BigInteger s2_e = sigBigInt2.pow(rsaPublicKey.getPublicExponent().intValue());
        LOG.debug("s2^e: " + s2_e);

        LOG.debug("calculating GCD...");
        LOG.debug("msg1: " + msgBigInt1);
        LOG.debug("msg2: " + msgBigInt2);
        BigInteger a = s1_e.subtract(msgBigInt1);
        BigInteger b = s2_e.subtract(msgBigInt2);
        LOG.debug("a: " + a);
        LOG.debug("b: " + b);
        BigInteger candidateModulus = a.gcd(b);
        LOG.debug("candidate modulus: " + candidateModulus);
        LOG.debug("candidate modulus size: " + candidateModulus.toByteArray().length);
        BigInteger s_e = s1_e.multiply(s2_e);
        BigInteger m = msgBigInt1.multiply(msgBigInt2);
        while (false == rsaPublicKey.getModulus().equals(candidateModulus)) {
            LOG.error("incorrect candidate modulus");
            LOG.debug("modulus | candidate modulus: "
                    + candidateModulus.remainder(rsaPublicKey.getModulus()).equals(BigInteger.ZERO));
            s_e = s_e.multiply(s1_e);
            m = m.multiply(msgBigInt1);
            BigInteger n1 = s_e.subtract(m).gcd(a);
            BigInteger n2 = s_e.subtract(m).gcd(b);
            candidateModulus = n1.gcd(n2);
            // try / 2
            LOG.debug("new modulus:       " + n1);
            LOG.debug("new modulus:       " + n2);
            LOG.debug("candidate modulus: " + candidateModulus);
            LOG.debug("actual mod:        " + rsaPublicKey.getModulus());
        }
    }
}

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