區塊鏈使用的加密和解密技術（JAVA版）

加密和解密是區塊鏈數據傳輸中不可缺少的技術點，現代密碼學包括對稱性加密和非對稱性加密兩個概念，區塊鏈系統裏面一般常用到的是非對稱加密。這裏把相關知識記錄一下。

（一）對稱加密（Symmetric Cryptography）

對稱加密是最快速、最簡單的一種加密方式，加密（encryption）與解密（decryption）用的是同樣的密鑰（secret key）。對稱加密有很多種算法，由於它效率很高，所以被廣泛使用在很多加密協議的核心當中。

對稱加密通常使用的是相對較小的密鑰，一般小於256 bit。因爲密鑰越大，加密越強，但加密與解密的過程越慢。如果你只用1 bit來做這個密鑰，那們可以先試着用0來解密，不行的話就再用1解；但如果你的密鑰有1 MB大，們可能永遠也無法破解，但加密和解密的過程要花費很長的時間。密鑰的大小既要照顧到安全性，也要照顧到效率，是一個trade-off。

所謂對稱加密算法即：加密和解密使用相同密鑰的算法。常見的有DES、3DES、AES、PBE等加密算法，這幾種算法安全性依次是逐漸增強的。

DES加密

DES是一種對稱加密算法，是一種非常簡便的加密算法，但是密鑰長度比較短。DES加密算法出自IBM的研究，後來被美國政府正式採用，之後開始廣泛流傳，但是近些年使用越來越少，因爲DES使用56位密鑰，以現代計算能力，24小時內即可被破解。

雖然如此，在某些簡單應用中，我們還是可以使用DES加密算法.

簡單的DES加密算法JAVA實現：

public class DESUtil {

private static final String KEY_ALGORITHM = "DES";
private static final String DEFAULT_CIPHER_ALGORITHM = "DES/ECB/PKCS5Padding";//默認的加密算法

/**
 * DES 加密操作
 *
 * @param content 待加密內容
 * @param key 加密密鑰
 * @return 返回Base64轉碼後的加密數據
 */
public static String encrypt(String content, String key) {
    try {
        Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);// 創建密碼器

        byte[] byteContent = content.getBytes("utf-8");

        cipher.init(Cipher.ENCRYPT_MODE, getSecretKey(key));// 初始化爲加密模式的密碼器

        byte[] result = cipher.doFinal(byteContent);// 加密

        return Base64.encodeBase64String(result);//通過Base64轉碼返回
    } catch (Exception ex) {
        Logger.getLogger(DESUtil.class.getName()).log(Level.SEVERE, null, ex);
    }

    return null;
}

/**
 * DES 解密操作
 *
 * @param content
 * @param key
 * @return
 */
public static String decrypt(String content, String key) {

    try {
        //實例化
        Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);

        //使用密鑰初始化，設置爲解密模式
        cipher.init(Cipher.DECRYPT_MODE, getSecretKey(key));

        //執行操作
        byte[] result = cipher.doFinal(Base64.decodeBase64(content));

        return new String(result, "utf-8");
    } catch (Exception ex) {
        Logger.getLogger(DESUtil.class.getName()).log(Level.SEVERE, null, ex);
    }

    return null;
}

/**
 * 生成加密祕鑰
 *
 * @return
 */
private static SecretKeySpec getSecretKey(final String key) {
    //返回生成指定算法密鑰生成器的 KeyGenerator 對象
    KeyGenerator kg = null;

    try {
        kg = KeyGenerator.getInstance(KEY_ALGORITHM);

        //DES 要求密鑰長度爲 56
        kg.init(56, new SecureRandom(key.getBytes()));

        //生成一個密鑰
        SecretKey secretKey = kg.generateKey();

        return new SecretKeySpec(secretKey.getEncoded(), KEY_ALGORITHM);// 轉換爲DES專用密鑰
    } catch (NoSuchAlgorithmException ex) {
        Logger.getLogger(DESUtil.class.getName()).log(Level.SEVERE, null, ex);
    }

    return null;
}

public static void main(String[] args) {
    String content = "hello,您好";
    String key = "sde@5f98H*^hsff%dfs$r344&df8543*er";
    System.out.println("content:" + content);
    String s1 = DESUtil.encrypt(content, key);
    System.out.println("s1:" + s1);
    System.out.println("s2:"+ DESUtil.decrypt(s1, key));

}

}

3DES加密

3DES是一種對稱加密算法，在 DES 的基礎上，使用三重數據加密算法，對數據進行加密，它相當於是對每個數據塊應用三次 DES 加密算法。由於計算機運算能力的增強，原版 DES 密碼的密鑰長度變得容易被暴力破解；3DES 即是設計用來提供一種相對簡單的方法，即通過增加 DES 的密鑰長度來避免類似的***，而不是設計一種全新的塊密碼算法這樣來說，破解的概率就小了很多。缺點由於使用了三重數據加密算法，可能會比較耗性能。簡單的3DES加密算法實現：
（略）

（二）非對稱加密

非對稱加密算法需要兩個密鑰：公開密鑰（publickey）和私有密鑰（privatekey）。公開密鑰與私有密鑰是一對，如果用公開密鑰對數據進行加密，只有用對應的私有密鑰才能解密；如果用私有密鑰對數據進行加密，那麼只有用對應的公開密鑰才能解密。一般公鑰是公開的，私鑰是自己保存。因爲加密和解密使用的是兩個不同的密鑰，所以這種算法叫作非對稱加密算法。安全性相對對稱加密來說更高，是一種高級加密方式。

RSA加密

RSA是一種非對稱加密算法.RSA有兩個密鑰，一個是公開的，稱爲公開密鑰；一個是私密的，稱爲私密密鑰。公開密鑰是對大衆公開的，私密密鑰是服務器私有的，兩者不能互推得出。用公開密鑰對數據進行加密，私密密鑰可解密；私密密鑰對數據加密，公開密鑰可解密。速度較對稱加密慢。

簡單的RSA加密算法JAVA實現：

/**

• <p>
• RSA公鑰/私鑰/簽名工具包
• </p>
• <p>
• 字符串格式的密鑰在未在特殊說明情況下都爲BASE64編碼格式<br/>
• 由於非對稱加密速度極其緩慢，一般文件不使用它來加密而是使用對稱加密，<br/>
• 非對稱加密算法可以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效率和安全
• </p>

• */
  public class RSAUtils {

  /**

  • 加密算法RSA
    */
    public static final String KEY_ALGORITHM = "RSA";

  /**

  • 簽名算法
    */
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

  /**

  • 獲取公鑰的key
    */
    private static final String PUBLIC_KEY = "RSAPublicKey";

  /**

  • 獲取私鑰的key
    */
    private static final String PRIVATE_KEY = "RSAPrivateKey";

  /**

  • 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;

  /**

  • <p>
  • 生成密鑰對(公鑰和私鑰)
  • </p>
  • @return
  • @throws Exception
    */
    public static Map<String, Object> genKeyPair() throws Exception {
    KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
    keyPairGen.initialize(1024);
    KeyPair keyPair = keyPairGen.generateKeyPair();
    RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
    RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
    Map<String, Object> keyMap = new HashMap<String, Object>(2);
    keyMap.put(PUBLIC_KEY, publicKey);
    keyMap.put(PRIVATE_KEY, privateKey);
    return keyMap;
    }

  /**

  • <p>
  • 用私鑰對信息生成數字簽名
  • </p>
  • @param data 已加密數據
  • @param privateKey 私鑰(BASE64編碼)
  • @return
  • @throws Exception
    */
    public static String sign(byte[] data, String privateKey) throws Exception {
    byte[] keyBytes = Base64Utils.decode(privateKey);
    PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);
    Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
    signature.initSign(privateK);
    signature.update(data);
    return Base64Utils.encode(signature.sign());
    }

  /**

  • <p>
  • 校驗數字簽名
  • </p>
  • @param data 已加密數據
  • @param publicKey 公鑰(BASE64編碼)
  • @param sign 數字簽名
  • @return
  • @throws Exception

  • */
    public static boolean verify(byte[] data, String publicKey, String sign)
    throws Exception {
    byte[] keyBytes = Base64Utils.decode(publicKey);
    X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    PublicKey publicK = keyFactory.generatePublic(keySpec);
    Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
    signature.initVerify(publicK);
    signature.update(data);
    return signature.verify(Base64Utils.decode(sign));
    }

  /**

  • <P>
  • 私鑰解密
  • </p>
  • @param encryptedData 已加密數據
  • @param privateKey 私鑰(BASE64編碼)
  • @return
  • @throws Exception
    /
    public static byte[] decryptByPrivateKey(byte[] encryptedData, String privateKey)
    throws Exception {
    byte[] keyBytes = Base64Utils.decode(privateKey);
    PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
    Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
    cipher.init(Cipher.DECRYPT_MODE, privateK);
    int inputLen = encryptedData.length;
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    int offSet = 0;
    byte[] cache;
    int i = 0;
    // 對數據分段解密
    while (inputLen - offSet > 0) {
    if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
    cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
    } else {
    cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
    }
    out.write(cache, 0, cache.length);
    i++;
    offSet = i MAX_DECRYPT_BLOCK;
    }
    byte[] decryptedData = out.toByteArray();
    out.close();
    return decryptedData;
    }

  /**

  • <p>
  • 公鑰解密
  • </p>
  • @param encryptedData 已加密數據
  • @param publicKey 公鑰(BASE64編碼)
  • @return
  • @throws Exception
    /
    public static byte[] decryptByPublicKey(byte[] encryptedData, String publicKey)
    throws Exception {
    byte[] keyBytes = Base64Utils.decode(publicKey);
    X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    Key publicK = keyFactory.generatePublic(x509KeySpec);
    Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
    cipher.init(Cipher.DECRYPT_MODE, publicK);
    int inputLen = encryptedData.length;
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    int offSet = 0;
    byte[] cache;
    int i = 0;
    // 對數據分段解密
    while (inputLen - offSet > 0) {
    if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
    cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
    } else {
    cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
    }
    out.write(cache, 0, cache.length);
    i++;
    offSet = i MAX_DECRYPT_BLOCK;
    }
    byte[] decryptedData = out.toByteArray();
    out.close();
    return decryptedData;
    }

  /**

  • <p>
  • 公鑰加密
  • </p>
  • @param data 源數據
  • @param publicKey 公鑰(BASE64編碼)
  • @return
  • @throws Exception
    /
    public static byte[] encryptByPublicKey(byte[] data, String publicKey)
    throws Exception {
    byte[] keyBytes = Base64Utils.decode(publicKey);
    X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    Key publicK = keyFactory.generatePublic(x509KeySpec);
    // 對數據加密
    Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
    cipher.init(Cipher.ENCRYPT_MODE, publicK);
    int inputLen = data.length;
    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 > MAX_ENCRYPT_BLOCK) {
    cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
    } else {
    cache = cipher.doFinal(data, offSet, inputLen - offSet);
    }
    out.write(cache, 0, cache.length);
    i++;
    offSet = i MAX_ENCRYPT_BLOCK;
    }
    byte[] encryptedData = out.toByteArray();
    out.close();
    return encryptedData;
    }

  /**

  • <p>
  • 私鑰加密
  • </p>
  • @param data 源數據
  • @param privateKey 私鑰(BASE64編碼)
  • @return
  • @throws Exception
    /
    public static byte[] encryptByPrivateKey(byte[] data, String privateKey)
    throws Exception {
    byte[] keyBytes = Base64Utils.decode(privateKey);
    PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
    Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
    cipher.init(Cipher.ENCRYPT_MODE, privateK);
    int inputLen = data.length;
    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 > MAX_ENCRYPT_BLOCK) {
    cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
    } else {
    cache = cipher.doFinal(data, offSet, inputLen - offSet);
    }
    out.write(cache, 0, cache.length);
    i++;
    offSet = i MAX_ENCRYPT_BLOCK;
    }
    byte[] encryptedData = out.toByteArray();
    out.close();
    return encryptedData;
    }

  /**

  • <p>
  • 獲取私鑰
  • </p>
  • @param keyMap 密鑰對
  • @return
  • @throws Exception
    */
    public static String getPrivateKey(Map<String, Object> keyMap)
    throws Exception {
    Key key = (Key) keyMap.get(PRIVATE_KEY);
    return Base64Utils.encode(key.getEncoded());
    }

  /**

  • <p>
  • 獲取公鑰
  • </p>
  • @param keyMap 密鑰對
  • @return
  • @throws Exception
    */
    public static String getPublicKey(Map<String, Object> keyMap)
    throws Exception {
    Key key = (Key) keyMap.get(PUBLIC_KEY);
    return Base64Utils.encode(key.getEncoded());
    }

}

/**

• <p>
• RSA公鑰/私鑰/簽名工具包
• </p>
• <p>
• 字符串格式的密鑰在未在特殊說明情況下都爲BASE64編碼格式<br/>
• 由於非對稱加密速度極其緩慢，一般文件不使用它來加密而是使用對稱加密，<br/>
• 非對稱加密算法可以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
• </p>

• */
  public class RSAUtils {

  /**

  • 加密算法RSA
    */
    public static final String KEY_ALGORITHM = "RSA";

  /**

  • 簽名算法
    */
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

  /**

  • 獲取公鑰的key
    */
    private static final String PUBLIC_KEY = "RSAPublicKey";

  /**

  • 獲取私鑰的key
    */
    private static final String PRIVATE_KEY = "RSAPrivateKey";

  /**

  • 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;

  /**

  • <p>
  • 生成密鑰對(公鑰和私鑰)
  • </p>
  • @return
  • @throws Exception
    */
    public static Map<String, Object> genKeyPair() throws Exception {
    KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
    keyPairGen.initialize(1024);
    KeyPair keyPair = keyPairGen.generateKeyPair();
    RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
    RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
    Map<String, Object> keyMap = new HashMap<String, Object>(2);
    keyMap.put(PUBLIC_KEY, publicKey);
    keyMap.put(PRIVATE_KEY, privateKey);
    return keyMap;
    }

  /**

  • <p>
  • 用私鑰對信息生成數字簽名
  • </p>
  • @param data 已加密數據
  • @param privateKey 私鑰(BASE64編碼)
  • @return
  • @throws Exception
    */
    public static String sign(byte[] data, String privateKey) throws Exception {
    byte[] keyBytes = Base64Utils.decode(privateKey);
    PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);
    Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
    signature.initSign(privateK);
    signature.update(data);
    return Base64Utils.encode(signature.sign());
    }

  /**

  • <p>
  • 校驗數字簽名
  • </p>
  • @param data 已加密數據
  • @param publicKey 公鑰(BASE64編碼)
  • @param sign 數字簽名
  • @return
  • @throws Exception

  • */
    public static boolean verify(byte[] data, String publicKey, String sign)
    throws Exception {
    byte[] keyBytes = Base64Utils.decode(publicKey);
    X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    PublicKey publicK = keyFactory.generatePublic(keySpec);
    Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
    signature.initVerify(publicK);
    signature.update(data);
    return signature.verify(Base64Utils.decode(sign));
    }

  /**

  • <P>
  • 私鑰解密
  • </p>
  • @param encryptedData 已加密數據
  • @param privateKey 私鑰(BASE64編碼)
  • @return
  • @throws Exception
    /
    public static byte[] decryptByPrivateKey(byte[] encryptedData, String privateKey)
    throws Exception {
    byte[] keyBytes = Base64Utils.decode(privateKey);
    PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
    Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
    cipher.init(Cipher.DECRYPT_MODE, privateK);
    int inputLen = encryptedData.length;
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    int offSet = 0;
    byte[] cache;
    int i = 0;
    // 對數據分段解密
    while (inputLen - offSet > 0) {
    if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
    cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
    } else {
    cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
    }
    out.write(cache, 0, cache.length);
    i++;
    offSet = i MAX_DECRYPT_BLOCK;
    }
    byte[] decryptedData = out.toByteArray();
    out.close();
    return decryptedData;
    }

  /**

  • <p>
  • 公鑰解密
  • </p>
  • @param encryptedData 已加密數據
  • @param publicKey 公鑰(BASE64編碼)
  • @return
  • @throws Exception
    /
    public static byte[] decryptByPublicKey(byte[] encryptedData, String publicKey)
    throws Exception {
    byte[] keyBytes = Base64Utils.decode(publicKey);
    X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    Key publicK = keyFactory.generatePublic(x509KeySpec);
    Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
    cipher.init(Cipher.DECRYPT_MODE, publicK);
    int inputLen = encryptedData.length;
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    int offSet = 0;
    byte[] cache;
    int i = 0;
    // 對數據分段解密
    while (inputLen - offSet > 0) {
    if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
    cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
    } else {
    cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
    }
    out.write(cache, 0, cache.length);
    i++;
    offSet = i MAX_DECRYPT_BLOCK;
    }
    byte[] decryptedData = out.toByteArray();
    out.close();
    return decryptedData;
    }

  /**

  • <p>
  • 公鑰加密
  • </p>
  • @param data 源數據
  • @param publicKey 公鑰(BASE64編碼)
  • @return
  • @throws Exception
    /
    public static byte[] encryptByPublicKey(byte[] data, String publicKey)
    throws Exception {
    byte[] keyBytes = Base64Utils.decode(publicKey);
    X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    Key publicK = keyFactory.generatePublic(x509KeySpec);
    // 對數據加密
    Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
    cipher.init(Cipher.ENCRYPT_MODE, publicK);
    int inputLen = data.length;
    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 > MAX_ENCRYPT_BLOCK) {
    cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
    } else {
    cache = cipher.doFinal(data, offSet, inputLen - offSet);
    }
    out.write(cache, 0, cache.length);
    i++;
    offSet = i MAX_ENCRYPT_BLOCK;
    }
    byte[] encryptedData = out.toByteArray();
    out.close();
    return encryptedData;
    }

  /**

  • <p>
  • 私鑰加密
  • </p>
  • @param data 源數據
  • @param privateKey 私鑰(BASE64編碼)
  • @return
  • @throws Exception
    /
    public static byte[] encryptByPrivateKey(byte[] data, String privateKey)
    throws Exception {
    byte[] keyBytes = Base64Utils.decode(privateKey);
    PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
    KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
    Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
    Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
    cipher.init(Cipher.ENCRYPT_MODE, privateK);
    int inputLen = data.length;
    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 > MAX_ENCRYPT_BLOCK) {
    cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
    } else {
    cache = cipher.doFinal(data, offSet, inputLen - offSet);
    }
    out.write(cache, 0, cache.length);
    i++;
    offSet = i MAX_ENCRYPT_BLOCK;
    }
    byte[] encryptedData = out.toByteArray();
    out.close();
    return encryptedData;
    }

  /**

  • <p>
  • 獲取私鑰
  • </p>
  • @param keyMap 密鑰對
  • @return
  • @throws Exception
    */
    public static String getPrivateKey(Map<String, Object> keyMap)
    throws Exception {
    Key key = (Key) keyMap.get(PRIVATE_KEY);
    return Base64Utils.encode(key.getEncoded());
    }

  /**

  • <p>
  • 獲取公鑰
  • </p>
  • @param keyMap 密鑰對
  • @return
  • @throws Exception
    */
    public static String getPublicKey(Map<String, Object> keyMap)
    throws Exception {
    Key key = (Key) keyMap.get(PUBLIC_KEY);
    return Base64Utils.encode(key.getEncoded());
    }

}

public class Base64Utils {

/**
 * 文件讀取緩衝區大小
 */
private static final int CACHE_SIZE = 1024;

/**
 * <p>
 * BASE64字符串解碼爲二進制數據
 * </p>
 *
 * @param base64
 * @return
 * @throws Exception
 */
public static byte[] decode(String base64) throws Exception {
    return Base64.decode(base64.getBytes());
}

/**
 * <p>
 * 二進制數據編碼爲BASE64字符串
 * </p>
 *
 * @param bytes
 * @return
 * @throws Exception
 */
public static String encode(byte[] bytes) throws Exception {
    return new String(Base64.encode(bytes));
}

/**
 * <p>
 * 將文件編碼爲BASE64字符串
 * </p>
 * <p>
 * 大文件慎用，可能會導致內存溢出
 * </p>
 *
 * @param filePath
 *            文件絕對路徑
 * @return
 * @throws Exception
 */
public static String encodeFile(String filePath) throws Exception {
    byte[] bytes = fileToByte(filePath);
    return encode(bytes);
}

/**
 * <p>
 * BASE64字符串轉回文件
 * </p>
 *
 * @param filePath
 *            文件絕對路徑
 * @param base64
 *            編碼字符串
 * @throws Exception
 */
public static void decodeToFile(String filePath, String base64) throws Exception {
    byte[] bytes = decode(base64);
    byteArrayToFile(bytes, filePath);
}

/**
 * <p>
 * 文件轉換爲二進制數組
 * </p>
 *
 * @param filePath
 *            文件路徑
 * @return
 * @throws Exception
 */
public static byte[] fileToByte(String filePath) throws Exception {
    byte[] data = new byte[0];
    File file = new File(filePath);
    if (file.exists()) {
        FileInputStream in = new FileInputStream(file);
        ByteArrayOutputStream out = new ByteArrayOutputStream(2048);
        byte[] cache = new byte[CACHE_SIZE];
        int nRead = 0;
        while ((nRead = in.read(cache)) != -1) {
            out.write(cache, 0, nRead);
            out.flush();
        }
        out.close();
        in.close();
        data = out.toByteArray();
    }
    return data;
}

/**
 * <p>
 * 二進制數據寫文件
 * </p>
 *
 * @param bytes
 *            二進制數據
 * @param filePath
 *            文件生成目錄
 */
public static void byteArrayToFile(byte[] bytes, String filePath) throws Exception {
    InputStream in = new ByteArrayInputStream(bytes);
    File destFile = new File(filePath);
    if (!destFile.getParentFile().exists()) {
        destFile.getParentFile().mkdirs();
    }
    destFile.createNewFile();
    OutputStream out = new FileOutputStream(destFile);
    byte[] cache = new byte[CACHE_SIZE];
    int nRead = 0;
    while ((nRead = in.read(cache)) != -1) {
        out.write(cache, 0, nRead);
        out.flush();
    }
    out.close();
    in.close();
}

}