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针对sm2和sm4两种加密算法的java实现
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package com.bouncycastle.crypto.tls;

import com.bouncycastle.asn1.sec.SECNamedCurves;
import com.bouncycastle.asn1.x9.X9ECParameters;
import com.bouncycastle.crypto.params.ECDomainParameters;

/**
 * RFC 4492 5.1.1
 * 
 * The named curves defined here are those specified in SEC 2 [13]. Note that many of
 * these curves are also recommended in ANSI X9.62 [7] and FIPS 186-2 [11]. Values 0xFE00
 * through 0xFEFF are reserved for private use. Values 0xFF01 and 0xFF02 indicate that the
 * client supports arbitrary prime and characteristic-2 curves, respectively (the curve
 * parameters must be encoded explicitly in ECParameters).
 */
public class NamedCurve
{
    public static final int sect163k1 = 1;
    public static final int sect163r1 = 2;
    public static final int sect163r2 = 3;
    public static final int sect193r1 = 4;
    public static final int sect193r2 = 5;
    public static final int sect233k1 = 6;
    public static final int sect233r1 = 7;
    public static final int sect239k1 = 8;
    public static final int sect283k1 = 9;
    public static final int sect283r1 = 10;
    public static final int sect409k1 = 11;
    public static final int sect409r1 = 12;
    public static final int sect571k1 = 13;
    public static final int sect571r1 = 14;
    public static final int secp160k1 = 15;
    public static final int secp160r1 = 16;
    public static final int secp160r2 = 17;
    public static final int secp192k1 = 18;
    public static final int secp192r1 = 19;
    public static final int secp224k1 = 20;
    public static final int secp224r1 = 21;
    public static final int secp256k1 = 22;
    public static final int secp256r1 = 23;
    public static final int secp384r1 = 24;
    public static final int secp521r1 = 25;

    /*
     * reserved (0xFE00..0xFEFF)
     */

    public static final int arbitrary_explicit_prime_curves = 0xFF01;
    public static final int arbitrary_explicit_char2_curves = 0xFF02;

    private static final String[] curveNames = new String[] {
        "sect163k1",
        "sect163r1",
        "sect163r2",
        "sect193r1",
        "sect193r2",
        "sect233k1",
        "sect233r1",
        "sect239k1",
        "sect283k1",
        "sect283r1",
        "sect409k1",
        "sect409r1",
        "sect571k1",
        "sect571r1",
        "secp160k1",
        "secp160r1",
        "secp160r2",
        "secp192k1",
        "secp192r1",
        "secp224k1",
        "secp224r1",
        "secp256k1",
        "secp256r1",
        "secp384r1",
        "secp521r1", };

    static ECDomainParameters getECParameters(int namedCurve)
    {
        int index = namedCurve - 1;
        if (index < 0 || index >= curveNames.length)
        {
            return null;
        }

        String curveName = curveNames[index];

        // Lazily created the first time a particular curve is accessed
        X9ECParameters ecP = SECNamedCurves.getByName(curveName);

        if (ecP == null)
        {
            return null;
        }

        // It's a bit inefficient to do this conversion every time
        return new ECDomainParameters(ecP.getCurve(), ecP.getG(), ecP.getN(), ecP.getH(),
            ecP.getSeed());
    }
}