JNIHelper.java

package com.catherine.securitysample;

import android.util.Base64;

import java.io.UnsupportedEncodingException;
import java.math.BigInteger;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.Key;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.RSAPublicKeySpec;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
/**
 * Created by Catherine on 2017/6/29.

 */

public class JNIHelper {
    static {
        //relate to LOCAL_MODULE in Android.mk
        System.loadLibrary("keys");
    }

    /**
     * Decrypt messages by RSA algorithm<br>
     *
     * @param message
     * @return Original message
     * @throws NoSuchAlgorithmException
     * @throws NoSuchPaddingException
     * @throws InvalidKeyException
     * @throws IllegalBlockSizeException
     * @throws BadPaddingException
     * @throws UnsupportedEncodingException
     * @throws InvalidAlgorithmParameterException
     * @throws InvalidKeySpecException
     * @throws ClassNotFoundException
     */
    public String decryptRSA(String message) throws NoSuchAlgorithmException, NoSuchPaddingException,
            InvalidKeyException, IllegalBlockSizeException, BadPaddingException, UnsupportedEncodingException,
            InvalidAlgorithmParameterException, ClassNotFoundException, InvalidKeySpecException {

        Cipher c2 = Cipher.getInstance(Algorithm.rules.get("RSA")); // 创建一个Cipher对象，注意这里用的算法需要和Key的算法匹配

        BigInteger m = new BigInteger(Base64.decode(getKeyParams()[0].getBytes(), Base64.DEFAULT));
        BigInteger e = new BigInteger(Base64.decode(getKeyParams()[1].getBytes(), Base64.DEFAULT));
        c2.init(Cipher.DECRYPT_MODE, convertStringToPublicKey(m, e)); // 设置Cipher为解密工作模式，需要把Key传进去
        byte[] decryptedData = c2.doFinal(Base64.decode(message.getBytes(), Base64.DEFAULT));
        return new String(decryptedData, Algorithm.CHARSET);
    }

    /**
     * You can component a publicKey by a specific pair of values - modulus and
     * exponent.
     *
     * @param modulus  When you generate a new RSA KeyPair, you'd get a PrivateKey, a
     *                 modulus and an exponent.
     * @param exponent When you generate a new RSA KeyPair, you'd get a PrivateKey, a
     *                 modulus and an exponent.
     * @throws ClassNotFoundException
     * @throws NoSuchAlgorithmException
     * @throws InvalidKeySpecException
     */
    private Key convertStringToPublicKey(BigInteger modulus, BigInteger exponent)
            throws ClassNotFoundException, NoSuchAlgorithmException, InvalidKeySpecException {
        byte[] modulusByteArry = modulus.toByteArray();
        byte[] exponentByteArry = exponent.toByteArray();

        // 由接收到的参数构造RSAPublicKeySpec对象
        RSAPublicKeySpec rsaPublicKeySpec = new RSAPublicKeySpec(new BigInteger(modulusByteArry),
                new BigInteger(exponentByteArry));
        // 根据RSAPublicKeySpec对象获取公钥对象
        KeyFactory kFactory = KeyFactory.getInstance(Algorithm.KEYPAIR_ALGORITHM);
        PublicKey publicKey = kFactory.generatePublic(rsaPublicKeySpec);
        return publicKey;
    }

    /**
     * A native method that is implemented by the 'native-lib' native library,
     * which is packaged with this application.
     */
    public native String[] getAuthChain(String key);

    /**
     * A native method that is implemented by the 'native-lib' native library,
     * which is packaged with this application.
     */
    public native String[] getKeyParams();
}