Android使用RSA加密和解密的示例代碼

2019-10-22 18:25:50

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一、公鑰加密和私鑰解密

  /**RSA算法*/  public static final String RSA = "RSA";  /**加密方式，android的*/// public static final String TRANSFORMATION = "RSA/None/NoPadding";  /**加密方式，標準jdk的*/  public static final String TRANSFORMATION = "RSA/None/PKCS1Padding";  /** 使用公鑰加密 */  public static byte[] encryptByPublicKey(byte[] data, byte[] publicKey) throws Exception {    // 得到公鑰對象    X509EncodedKeySpec keySpec = new X509EncodedKeySpec(publicKey);    KeyFactory keyFactory = KeyFactory.getInstance("RSA");    PublicKey pubKey = keyFactory.generatePublic(keySpec);    // 加密數據    Cipher cp = Cipher.getInstance(TRANSFORMATION);    cp.init(Cipher.ENCRYPT_MODE, pubKey);    return cp.doFinal(data);  }  /** 使用私鑰解密 */  public static byte[] decryptByPrivateKey(byte[] encrypted, byte[] privateKey) throws Exception {    // 得到私鑰對象    PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(privateKey);    KeyFactory kf = KeyFactory.getInstance(RSA);    PrivateKey keyPrivate = kf.generatePrivate(keySpec);    // 解密數據    Cipher cp = Cipher.getInstance(TRANSFORMATION);    cp.init(Cipher.DECRYPT_MODE, keyPrivate);    byte[] arr = cp.doFinal(encrypted);    return arr;  }

1.data是要加密的數據，如果是字符串則getBytes。publicKey是公鑰，privateKey是私鑰。自定義密鑰對測試

  String data = "hello world";  try {    int keyLength = 1024;    //生成密鑰對    KeyPair keyPair = RSAUtils.generateRSAKeyPair(keyLength);    //獲取公鑰    byte[] publicKey = RSAUtils.getPublicKey(keyPair);    //獲取私鑰    byte[] privateKey = RSAUtils.getPrivateKey(keyPair);        //用公鑰加密    byte[] encrypt = RSAUtils.encryptByPublicKey(data.getBytes(), publicKey);    Log.d("TAG", "加密后的數據：" + StringUtils.byteArrayToString(encrypt));        //用私鑰解密    byte[] decrypt = RSAUtils.decryptByPrivateKey(encrypt, privateKey);    Log.d("TAG", "解密后的數據：" + new String(decrypt, "utf-8"));  } catch (Exception e) {    e.printStackTrace();  }

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2.從文件中讀取公鑰

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    String data = "hello world";    //讀取公鑰文件    String publicKeyString = IOUtils.readAssetsFile(this, "rsa_public_key.pem");    //base64解碼    byte[] publicKey = Base64Utils.decodeToBytes(publicKeyString);        try {      //加密      byte[] encrypt = RSAUtils.encryptByPublicKey(data.getBytes(), publicKey);      Log.d("TAG", "加密后的數據：" + StringUtils.byteArrayToString(encrypt));      //     //讀取私鑰文件//     String privateKeyString = IOUtils.readAssetsFile(this, "rsa_private_key.pem");//     //base64解碼//     byte[] privateKey = Base64Utils.decodeToBytes(privateKeyString);//     //解密//     byte[] decrypt = RSAUtils.decryptByPrivateKey(encrypt, privateKey);//     Log.d("TAG", "解密后的數據：" + new String(decrypt, "utf-8"));    } catch (Exception e) {      e.printStackTrace();    }

二、公鑰分段加密和私鑰分段解密

當加密的數據過長時，會出現javax.crypto.IllegalBlockSizeException: Data must not be longer than 117 bytes的異常。rsa算法規定一次加密的數據不能超過生成密鑰對時的keyLength/8-11，keyLength一般是1024個字節，則加密的數據不能超過117個字節

  /**秘鑰默認長度*/  public static final int DEFAULT_KEY_SIZE = 1024;  /**加密的數據最大的字節數，即117個字節*/  public static final int DEFAULT_BUFFERSIZE = (DEFAULT_KEY_SIZE / 8) - 11;  /**當加密的數據超過DEFAULT_BUFFERSIZE，則使用分段加密*/  public static final byte[] DEFAULT_SPLIT = "#PART#".getBytes();  /** 使用公鑰分段加密 */  public static byte[] encryptByPublicKeyForSpilt(byte[] data, byte[] publicKey) throws Exception{    int dataLen = data.length;    if (dataLen <= DEFAULT_BUFFERSIZE) {      return encryptByPublicKey(data, publicKey);    }    List<Byte> allBytes = new ArrayList<Byte>(2048);    int bufIndex = 0;    int subDataLoop = 0;    byte[] buf = new byte[DEFAULT_BUFFERSIZE];    for (int i = 0; i < dataLen; i++) {      buf[bufIndex] = data[i];      if (++bufIndex == DEFAULT_BUFFERSIZE || i == dataLen - 1) {        subDataLoop++;        if (subDataLoop != 1) {          for (byte b : DEFAULT_SPLIT) {            allBytes.add(b);          }        }        byte[] encryptBytes = encryptByPublicKey(buf, publicKey);        for (byte b : encryptBytes) {          allBytes.add(b);        }        bufIndex = 0;        if (i == dataLen - 1) {          buf = null;        } else {          buf = new byte[Math              .min(DEFAULT_BUFFERSIZE, dataLen - i - 1)];        }      }    }    byte[] bytes = new byte[allBytes.size()];    int i = 0;    for (Byte b : allBytes) {      bytes[i++] = b.byteValue();    }    return bytes;  }  /** 使用私鑰分段解密 */  public static byte[] decryptByPrivateKeyForSpilt(byte[] encrypted, byte[] privateKey) throws Exception {    int splitLen = DEFAULT_SPLIT.length;    if (splitLen <= 0) {      return decryptByPrivateKey(encrypted, privateKey);    }    int dataLen = encrypted.length;    List<Byte> allBytes = new ArrayList<Byte>(1024);    int latestStartIndex = 0;    for (int i = 0; i < dataLen; i++) {      byte bt = encrypted[i];      boolean isMatchSplit = false;      if (i == dataLen - 1) {        // 到data的最后了        byte[] part = new byte[dataLen - latestStartIndex];        System.arraycopy(encrypted, latestStartIndex, part, 0, part.length);        byte[] decryptPart = decryptByPrivateKey(part, privateKey);        for (byte b : decryptPart) {          allBytes.add(b);        }        latestStartIndex = i + splitLen;        i = latestStartIndex - 1;      } else if (bt == DEFAULT_SPLIT[0]) {        // 這個是以split[0]開頭        if (splitLen > 1) {          if (i + splitLen < dataLen) {            // 沒有超出data的范圍            for (int j = 1; j < splitLen; j++) {              if (DEFAULT_SPLIT[j] != encrypted[i + j]) {                break;              }              if (j == splitLen - 1) {                // 驗證到split的最后一位，都沒有break，則表明已經確認是split段                isMatchSplit = true;              }            }          }        } else {          // split只有一位，則已經匹配了          isMatchSplit = true;        }      }      if (isMatchSplit) {        byte[] part = new byte[i - latestStartIndex];        System.arraycopy(encrypted, latestStartIndex, part, 0, part.length);        byte[] decryptPart = decryptByPrivateKey(part, privateKey);        for (byte b : decryptPart) {          allBytes.add(b);        }        latestStartIndex = i + splitLen;        i = latestStartIndex - 1;      }    }    byte[] bytes = new byte[allBytes.size()];    int i = 0;    for (Byte b : allBytes) {      bytes[i++] = b.byteValue();    }    return bytes;  }

測試分段加密和解密

    String data = "hello world hello world hello world hello world hello world hello world hello world hello world " +        "hello world hello world hello world hello world hello world hello world hello world hello world hello world " +        "hello world hello world hello world hello world hello world hello world hello world hello world hello world ";    Log.d("TAG", "要加密的數據：" + data + ", 要加密的數據長度：" + data.length());    try {      //分段加密      byte[] encrypt = RSAUtils.encryptByPublicKeyForSpilt(data.getBytes(), publicKey);      Log.d("TAG", "加密后的數據：" + StringUtils.byteArrayToString(encrypt));            //分段解密      byte[] decrypt = RSAUtils.decryptByPrivateKeyForSpilt(encrypt, privateKey);      Log.d("TAG", "解密后的數據：" + new String(decrypt, "utf-8"));    } catch (Exception e) {      e.printStackTrace();    }

三、生成密鑰對

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  /** 生成密鑰對，即公鑰和私鑰。key長度是512-2048，一般為1024 */  public static KeyPair generateRSAKeyPair(int keyLength) throws NoSuchAlgorithmException {    KeyPairGenerator kpg = KeyPairGenerator.getInstance(RSA);    kpg.initialize(keyLength);    return kpg.genKeyPair();  }  /** 獲取公鑰，打印為48-12613448136942-12272-122-913111503-126115048-12...等等一長串用-拼接的數字 */  public static byte[] getPublicKey(KeyPair keyPair) {    RSAPublicKey rsaPublicKey = (RSAPublicKey) keyPair.getPublic();    return rsaPublicKey.getEncoded();  }  /** 獲取私鑰，同上 */  public static byte[] getPrivateKey(KeyPair keyPair) {    RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) keyPair.getPrivate();    return rsaPrivateKey.getEncoded();  }

生成公鑰和私鑰后，用base64編碼

    int keyLength = 1024;    try {      //生成密鑰對      KeyPair keyPair = RSAUtils.generateRSAKeyPair(keyLength);      //獲取公鑰      byte[] publicKey = RSAUtils.getPublicKey(keyPair);      Log.d("TAG", "公鑰：" + StringUtils.byteArrayToString(publicKey));      //公鑰用base64編碼      String encodePublic = Base64Utils.encodeToString(publicKey);      Log.d("TAG", "base64編碼的公鑰：" + encodePublic);      //獲取私鑰      byte[] privateKey = RSAUtils.getPrivateKey(keyPair);      Log.d("TAG", "私鑰：" + StringUtils.byteArrayToString(privateKey));      //私鑰用base64編碼      String encodePrivate = Base64Utils.encodeToString(privateKey);      Log.d("TAG", "base64編碼的私鑰：" + encodePrivate);    } catch (NoSuchAlgorithmException e) {      e.printStackTrace();    }

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