Code example for BigInteger

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public class EncryptionUtils { 
    private static final String TAG = EncryptionUtils.class.getSimpleName();
    private static final SecureRandom secureRandom = new SecureRandom();
 
    public static class ECDH { 
        private static final BigInteger q = new BigInteger("FFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFF", 16);
        private static final BigInteger a = new BigInteger("FFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFC", 16);
        private static final BigInteger b = new BigInteger("5AC635D8AA3A93E7B3EBBD55769886BC651D06B0CC53B0F63BCE3C3E27D2604B", 16);
        private static final BigInteger n = new BigInteger("FFFFFFFF00000000FFFFFFFFFFFFFFFFBCE6FAADA7179E84F3B9CAC2FC632551", 16);
 
        private static final ECFieldElement x = new ECFieldElement.Fp(q, new BigInteger("6B17D1F2E12C4247F8BCE6E563A440F277037D812DEB33A0F4A13945D898C296", 16));
        private static final ECFieldElement y = new ECFieldElement.Fp(q, new BigInteger("4FE342E2FE1A7F9B8EE7EB4A7C0F9E162BCE33576B315ECECBB6406837BF51F5", 16));
 
        private static final ECCurve curve = new ECCurve.Fp(q, a, b);
        private static final ECPoint g = new ECPoint.Fp(curve, x, y, true);
 
        public static final ECDomainParameters DOMAIN_PARAMETERS = new ECDomainParameters(curve, g, n);
 
        public static ECKeyPair generateKeyPair() { 
            ECKeyGenerationParameters keyParams = new ECKeyGenerationParameters(DOMAIN_PARAMETERS, secureRandom);
            ECKeyPairGenerator ecKeyPairGenerator = new ECKeyPairGenerator();