RSA非對稱加密

import javax.crypto.Cipher;
import java.io.InputStream;
import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

/**
 *@Author 黃俊聰
 *@Date 2017/12/15 17:29
 *@Description 非對稱加密解密工具類
 */
public class RSAUtil {

    /**
     * 私鑰字元串
     */
    private static String PRIVATE_KEY ="";
    /**
     * 公鑰字元串
     */
    private static String PUBLIC_KEY ="MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCbpmF28RgRDMduGSDhB2CD 0CiOFYytTGxYQuffq5RTgdoxxsE/3dgE+qQaDsTG1yzOwwCq7X3Xye7MZlcL 5SjNiLzh5tSEG7qyAVUfAgit1gYczWM+sTg+G7pnHa/omukvOfEeWceS8P35 Xt3ShqIeKfGxU4UIdiqKonBrQtYT/wIDAQAB";


    public static final String KEY_ALGORITHM = "RSA";

    /**
     * 讀取密鑰字元串
     * @throws Exception
     */

    public static void convert() throws Exception {
        byte[] data = null;

        try {
            InputStream is = RSAUtil.class.getResourceAsStream("/enc_pri");
            int length = is.available();
            data = new byte[length];
            is.read(data);
        } catch (Exception e) {
        }

        String dataStr = new String(data);
        try {
            PRIVATE_KEY = dataStr;
        } catch (Exception e) {
        }

        if (PRIVATE_KEY == null) {
            throw new Exception("Fail to retrieve key");
        }
    }

    /**
     *@Author 黃俊聰
     *@Date 2017/12/15 18:09
     *@Description RSA私鑰解密
     */
    public static byte[] decryptByPrivateKey(byte[] data) throws Exception {
        //從流中讀取密鑰字元串
        convert();
        //base64解碼
        byte[] keyBytes = Base64Util.decode(PRIVATE_KEY);
        //用PKCS8EncodedKeySpec這種模式解密
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        //選用RSA非對稱算法進行解密
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        //擷取私鑰
        Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);

        //用RSA算法擷取Cipher
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        //初始化解密模式
        cipher.init(Cipher.DECRYPT_MODE,privateKey);

        return cipher.doFinal(data);
    }

    /**
     *@Author 黃俊聰
     *@Date 2017/12/15 18:18
     *@Description RSA公鑰加密
     */
    public static byte[] encryptByPublicKey(byte[] data, String key) throws Exception {
        //base64解碼
        byte[] keyBytes = Base64Util.decode(key);
        //用X509EncodedKeySpec這種模式加密
        X509EncodedKeySpec pkcs8KeySpec = new X509EncodedKeySpec(keyBytes);
        //選用RSA非對稱算法進行加密
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        //擷取公鑰
        Key publicKey = keyFactory.generatePublic(pkcs8KeySpec);

        //用RSA算法擷取Cipher
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        //初始化加密模式
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        return cipher.doFinal(data);
    }


    public static void main(String[] args) throws Exception {
//        //根據RSA生成一對key,即公鑰和私鑰
//        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(KEY_ALGORITHM);
//        //設定key的大小，1024K
//        keyPairGenerator.initialize(1024);
//        //擷取key對的對象
//        KeyPair keyPair = keyPairGenerator.generateKeyPair();
//        //擷取私鑰
//        PrivateKey privateKey = keyPair.getPrivate();
//        //擷取公鑰
//        PublicKey publicKey = keyPair.getPublic();
//        System.out.println(Base64Util.encode(publicKey.getEncoded()));
//        System.out.println(Base64Util.encode(privateKey.getEncoded()));

        String data = "黃俊聰來了";
        byte[] enResult = encryptByPublicKey(data.getBytes("UTF-8"), PUBLIC_KEY);
        System.out.println(enResult.toString());
        byte[] deResult = decryptByPrivateKey(enResult);
        System.out.println(new String(deResult,"UTF-8"));
    }

//Base64工具類

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class Base64Util {
    private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
            .toCharArray();



    public static String encode(byte[] data) {
        byte start = 0;
        int len = data.length;
        StringBuffer buf = new StringBuffer(data.length * 3 / 2);
        int end = len - 3;
        int i = start;
        int n = 0;

        int d;
        while (i <= end) {
            d = (data[i] & 255) << 16 | (data[i + 1] & 255) << 8 | data[i + 2] & 255;
            buf.append(legalChars[d >> 18 & 63]);
            buf.append(legalChars[d >> 12 & 63]);
            buf.append(legalChars[d >> 6 & 63]);
            buf.append(legalChars[d & 63]);
            i += 3;
            if (n++ >= 14) {
                n = 0;
                buf.append(" ");
            }
        }

        if (i == start + len - 2) {
            d = (data[i] & 255) << 16 | (data[i + 1] & 255) << 8;
            buf.append(legalChars[d >> 18 & 63]);
            buf.append(legalChars[d >> 12 & 63]);
            buf.append(legalChars[d >> 6 & 63]);
            buf.append("=");
        } else if (i == start + len - 1) {
            d = (data[i] & 255) << 16;
            buf.append(legalChars[d >> 18 & 63]);
            buf.append(legalChars[d >> 12 & 63]);
            buf.append("==");
        }

        return buf.toString();
    }

    private static int decode(char c) {
        if (c >= 65 && c <= 90) {
            return c - 65;
        } else if (c >= 97 && c <= 122) {
            return c - 97 + 26;
        } else if (c >= 48 && c <= 57) {
            return c - 48 + 26 + 26;
        } else {
            switch (c) {
            case '+':
                return 62;
            case '/':
                return 63;
            case '=':
                return 0;
            default:
                throw new RuntimeException("unexpected code: " + c);
            }
        }
    }

    public static byte[] decode(String s) {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();

        try {
            decode(s, bos);
        } catch (IOException var5) {
            throw new RuntimeException();
        }

        byte[] decodedBytes = bos.toByteArray();

        try {
            bos.close();
            bos = null;
        } catch (IOException var4) {
            System.err.println("Error while decoding BASE64: " + var4.toString());
        }

        return decodedBytes;
    }

    private static void decode(String s, OutputStream os) throws IOException {
        int i = 0;
        int len = s.length();

        while (true) {
            while (i < len && s.charAt(i) <= 32) {
                ++i;
            }

            if (i == len) {
                break;
            }

            int tri = (decode(s.charAt(i)) << 18) + (decode(s.charAt(i + 1)) << 12) + (decode(s.charAt(i + 2)) << 6)
                    + decode(s.charAt(i + 3));
            os.write(tri >> 16 & 255);
            if (s.charAt(i + 2) == 61) {
                break;
            }

            os.write(tri >> 8 & 255);
            if (s.charAt(i + 3) == 61) {
                break;
            }

            os.write(tri & 255);
            i += 4;
        }

    }

}