RSA 加密解密

import org.apache.commons.codec.binary.Base64;
import org.junit.Test;

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

/**
 * 字符串格式的密鑰在未在特殊說明狀況下都爲BASE64編碼格式<br/>
 * 因爲非對稱加密速度極其緩慢，通常文件不使用它來加密而是使用對稱加密，<br/>
 * 非對稱加密算法能夠用來對對稱加密的密鑰加密，這樣保證密鑰的安全也就保證了數據的安全
 */
public class RSAEncrypterTest {

    /**
     * 加密算法RSA
     */
    private static final String KEY_ALGORITHM = "RSA";
    /**
     * 簽名算法
     */
    private static final String CIPHER_ALGORITHM = "RSA/ECB/PKCS1Padding";//RSA是加密方法，ECB是加密模式，PKCS1Padding是填充方式
    /**
     * 私鑰
     * openssl pkcs8 -topk8 -inform PEM -in p_key.pem -outform PEM -nocrypt
     */
    private static final String PRIVATE_KEY = "" + "MIICdwIBADANBgkqhkiG9w0BAQEFAASCAmEwggJdAgEAAoGBAPMhwl+bv8MlboJf" + "u6W5ec0SoQQxsHn8fHmfIEvWpLc1K6uiycJfOR4nHz2hRPMquw5uuz/yWvDUkrcl" + "dabWKuI9tq2kv8Kxv1M2E+9DE+ySCKqsrAp/XZMlsy8DP+fkPEATQRv4EUkH5eD6" + "x+0BlOpbZVtXdC7vyWeGSPOwldiRAgMBAAECgYBZ5ozB34xbszaWnKF9GQURsCa7" + "r0frA1Jfglhl0ntbhxybvXjPF3i+Tob9uekN5Sn/nzA75/h6fo+1ivNi+mQmRVf2" + "6h5/kfRYy0y3RNPFOTnd6B36etUx6EpzXlpT/q+igRqlu4ts4P1heBGOdqtLlSp9" + "0KqHnjieFEgMpMschQJBAP1HdyYoSJwbYd5J3DpUIEpfjIn1MkJ2OyrEk6MQypqF" + "G8ilOJCMsFFW8oY6pPPYT9z+3NwPqxz+UWU9Kv9WjXcCQQD1vmNcAB4eg99uEExs" + "WOHEcWFNZ654K/iJ915A/c7cIJSBkoe80kqDYg+UXuY/r7ZuUi3zPSECZzs4ge8H" + "+yw3AkEAzPSM1WLZxwFdhAzO2qCC9Mw3JNg3EJMuM+CY++a1nK7EGeyhRk+iyl+K" + "p9ZC71QG5HWU8br4I+EkqsEBz1gR5wJAf8/kEaemAq0H+lDTzs5zrh5iQ0YXwjzs" + "aaWVCix3+JmhY7r4ika9ppPMEplBHAKh2cM4TviOQJe8f2llDzueBQJBAPaYpKS7" + "fTh7xi5WkJrStcNVOVgThxgmIEg3mGTztBMe87WTgUAPMr4N9gewNf+5jx231cFB" + "3gYkkPgWNOYL/2Y=";
    /**
     * 公鑰
     */
    private static final String PUBLIC_KEY = "" + "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDzIcJfm7/DJW6CX7uluXnNEqEE" + "MbB5/Hx5nyBL1qS3NSurosnCXzkeJx89oUTzKrsObrs/8lrw1JK3JXWm1iriPbat" + "pL/Csb9TNhPvQxPskgiqrKwKf12TJbMvAz/n5DxAE0Eb+BFJB+Xg+sftAZTqW2Vb" + "V3Qu78lnhkjzsJXYkQIDAQAB";
    /**
     * RSA最大加密明文大小
     */
    private static final int MAX_ENCRYPT_BLOCK = 117;
    /**
     * RSA最大解密密文大小
     */
    private static final int MAX_DECRYPT_BLOCK = 128;

    @Test
    public void decodeTest() throws Exception {
        String data = "g08ZvPcrV+k8Fh1wJ8BRGDGJWOV6pm6aq6G+Q0vgfS4SQXAXx1DI9r489cs9krBu/2Okm1g4tvqzESWHW/" + "HFqFdsgYAHluN/x6mOAx4WTYYw5XlWCYdEUhhfHeUhZi9WR0omKCrFgSfyNWx5OPy/35PSLuvl5df5E30ewejDM9+tV8" + "pAr/lDQD30BE/XwH2Hvc1EdsZ54kncK2v7lOvmMNR3PmjVsryQNnuy4kqUY5yOqi7VJlf8atOheCUe+psrnJauDc32m/" + "R99hE1UhD/R8j7Df9ZptbL/37GOpyeCyRrBpGaSjUDJ2YmiS3AnA2hoeDVV5eT72J8P5EPFYuDGQ==";
        PrivateKey privateKey = getPrivateKey(PRIVATE_KEY);
        Cipher vDeCipher = Cipher.getInstance(CIPHER_ALGORITHM);
        vDeCipher.init(Cipher.DECRYPT_MODE, privateKey);
        //私鑰解密
        byte[] decrypted = autoFinal(Base64.decodeBase64(data.getBytes()), vDeCipher, MAX_DECRYPT_BLOCK);
        System.out.println("解密後：" + new String(decrypted, "utf-8"));
    }

    @Test
    public void baseTest() throws Exception {
        PrivateKey privateKey = getPrivateKey(PRIVATE_KEY);
        PublicKey publicKey = getPublicKey(PUBLIC_KEY);
        String data = "RSA加密明文最大長度117字節，解密要求密文最大長度爲128字節，因此在加密和解密的過程當中須要分塊進行。";
        //--
        Cipher pEnCipher = Cipher.getInstance(CIPHER_ALGORITHM);//java默認"RSA"="RSA/ECB/PKCS1Padding"
        pEnCipher.init(Cipher.ENCRYPT_MODE, publicKey);
        Cipher vDeCipher = Cipher.getInstance(CIPHER_ALGORITHM);
        vDeCipher.init(Cipher.DECRYPT_MODE, privateKey);
        //--
        Cipher vEnCipher = Cipher.getInstance(CIPHER_ALGORITHM);
        vEnCipher.init(Cipher.ENCRYPT_MODE, privateKey);
        Cipher pDeCipher = Cipher.getInstance(CIPHER_ALGORITHM);
        pDeCipher.init(Cipher.DECRYPT_MODE, publicKey);
        //公鑰加密
        byte[] encrypted = Base64.encodeBase64(autoFinal(data.getBytes("utf-8"), pEnCipher, MAX_ENCRYPT_BLOCK));
        System.out.println("加密後：" + new String(encrypted));
        //私鑰解密
        byte[] decrypted = autoFinal(Base64.decodeBase64(encrypted), vDeCipher, MAX_DECRYPT_BLOCK);
        System.out.println("解密後：" + new String(decrypted, "utf-8"));
        //私鑰加密
        byte[] encrypted2 = Base64.encodeBase64(autoFinal(data.getBytes("utf-8"), vEnCipher, MAX_ENCRYPT_BLOCK));
        System.out.println("加密後：" + new String(encrypted2));
        //公鑰解密
        byte[] decrypted2 = autoFinal(Base64.decodeBase64(encrypted2), pDeCipher, MAX_DECRYPT_BLOCK);
        System.out.println("解密後：" + new String(decrypted2, "utf-8"));
    }

    /**
     * 將base64編碼後的公鑰字符串轉成PublicKey實例
     */
    private static PublicKey getPublicKey(String publicKey) throws Exception {
        byte[] keyBytes = new Base64().decode(publicKey.getBytes());
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        return keyFactory.generatePublic(keySpec);
    }

    /**
     * 將base64編碼後的私鑰字符串轉成PrivateKey實例
     */
    private static PrivateKey getPrivateKey(String privateKey) throws Exception {
        byte[] keyBytes = new Base64().decode(privateKey.getBytes());
        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        return keyFactory.generatePrivate(keySpec);
    }

    private static byte[] autoFinal(byte[] data, Cipher cipher, int blockSize) throws Exception {
        int inputLen = data.length;
        byte[] rs;
        try (ByteArrayOutputStream out = new ByteArrayOutputStream()) {
            int offSet = 0;
            byte[] cache;
            int i = 0;
            // 對數據分段加密
            while (inputLen - offSet > 0) {
                if (inputLen - offSet > blockSize) {
                    cache = cipher.doFinal(data, offSet, blockSize);
                } else {
                    cache = cipher.doFinal(data, offSet, inputLen - offSet);
                }
                out.write(cache, 0, cache.length);
                i++;
                offSet = i * blockSize;
            }
            rs = out.toByteArray();
        }
        return rs;
}
}