RSA 非對稱加密算法

RSA 非對稱加密算法：

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.security.Key;
import java.security.KeyPair;
import java.security.KeyPairGenerator;

import javax.crypto.Cipher;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

@SuppressWarnings("restriction")
public class RSAEncrypt {
    /** 指定加密算法爲RSA */
    private static final String ALGORITHM = "RSA";
    /** 密鑰長度，用來初始化 */
    private static final int KEYSIZE = 1024;
    /** 指定公鑰存放文件 */
    private static String PUBLIC_KEY_FILE = "src/main/resources/META-INF/key/PublicKey";
    /** 指定私鑰存放文件 */
    private static String PRIVATE_KEY_FILE = "src/main/resources/META-INF/key/PrivateKey";

    /**
     * 生成密鑰對
     * 
     * @throws Exception
     */
    @SuppressWarnings("unused")
    private static void generateKeyPair() throws Exception {

        // /** RSA算法要求有一個可信任的隨機數源 */
        // SecureRandom secureRandom = new SecureRandom();

        /** 爲RSA算法創建一個KeyPairGenerator對象 */
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);

        /** 利用上面的隨機數據源初始化這個KeyPairGenerator對象 */
        // keyPairGenerator.initialize(KEYSIZE, secureRandom);
        keyPairGenerator.initialize(KEYSIZE);

        /** 生成密匙對 */
        KeyPair keyPair = keyPairGenerator.generateKeyPair();

        /** 得到公鑰 */
        Key publicKey = keyPair.getPublic();

        /** 得到私鑰 */
        Key privateKey = keyPair.getPrivate();

        ObjectOutputStream oos1 = null;
        ObjectOutputStream oos2 = null;
        try {
            /** 用對象流將生成的密鑰寫入文件 */
            oos1 = new ObjectOutputStream(
                    new FileOutputStream(RSAEncrypt.findProjectRootPath().concat(PUBLIC_KEY_FILE)));
            oos2 = new ObjectOutputStream(
                    new FileOutputStream(RSAEncrypt.findProjectRootPath().concat(PRIVATE_KEY_FILE)));
            oos1.writeObject(publicKey);
            oos2.writeObject(privateKey);
        } catch (Exception e) {
            throw e;
        } finally {
            /** 清空緩存，關閉文件輸出流 */
            oos1.close();
            oos2.close();
        }
    }

    /**
     * 加密方法
     * 
     * @param source
     *            源數據
     * @return
     * @throws Exception
     */
    public static String encrypt(String source) throws Exception {
        // generateKeyPair();
        Key publicKey;
        ObjectInputStream ois = null;
        try {
            /** 將文件中的公鑰對象讀出 */
            ois = new ObjectInputStream(new FileInputStream(RSAEncrypt.findProjectRootPath().concat(PUBLIC_KEY_FILE)));
            publicKey = (Key) ois.readObject();
        } catch (Exception e) {
            throw e;
        } finally {
            ois.close();
        }

        /** 得到Cipher對象來實現對源數據的RSA加密 */
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        byte[] b = source.getBytes();
        /** 執行加密操作 */
        byte[] b1 = cipher.doFinal(b);
        BASE64Encoder encoder = new BASE64Encoder();
        return encoder.encode(b1);
    }

    /**
     * 解密算法
     * 
     * @param cryptograph
     *            密文
     * @return
     * @throws Exception
     */
    public static String decrypt(String cryptograph) throws Exception {
        Key privateKey;
        ObjectInputStream ois = null;
        try {
            /** 將文件中的私鑰對象讀出 */
            ois = new ObjectInputStream(new FileInputStream(RSAEncrypt.findProjectRootPath().concat(PRIVATE_KEY_FILE)));
            privateKey = (Key) ois.readObject();
        } catch (Exception e) {
            throw e;
        } finally {
            ois.close();
        }

        /** 得到Cipher對象對已用公鑰加密的數據進行RSA解密 */
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        BASE64Decoder decoder = new BASE64Decoder();
        byte[] b1 = decoder.decodeBuffer(cryptograph);

        /** 執行解密操作 */
        byte[] b = cipher.doFinal(b1);
        return new String(b);
    }

    public static String findProjectRootPath() {
        /*
         * This method in the jar package access path is not correct
         */
        // RSAEncrypt encrypt = new RSAEncrypt();
        // String path =
        // encrypt.getClass().getResource("").toString().replace("file:/", "");
        // path = path.substring(0, path.indexOf("live/target") + 5);

        /*
         * This method is based on the current file to obtain an absolute
         * address
         * 
         */
        return new File("").getAbsolutePath().replaceAll("\\\\", "//").concat("/");
    };