如何解决Flutter (Dart) 中的 AES/GCM 加密
我正在尝试在颤振中实现 AES/GCM/nopadding 加密。我已经在 JAVA 中成功实现了它,但是当我尝试在 Flutter 中解密它时,我没有成功。
我曾尝试在 dart 中编写解密代码,但我得到了 未处理的异常:SecretBox 的消息身份验证代码 (MAC) 错误
我的 Java 代码
public class Gcmencryption {
public static final int AES_KEY_SIZE = 128;
public static final int GCM_IV_LENGTH = 12;
public static final int GCM_TAG_LENGTH = 16;
public String getEncryptedText(String plainText) {
try {
byte[] IV = new byte[GCM_IV_LENGTH];
SecureRandom random = new SecureRandom();
random.nextBytes(IV);
String iv = Base64.getEncoder().encodetoString(IV);
System.out.println("IV : "+iv);
byte[] cipherText = encrypt(plainText.getBytes(),getKeySpec(),IV);
String text = Base64.getEncoder().encodetoString(cipherText);
text = iv+text; // Concating iv and encrypted text together
return text;
} catch (Exception e) {
e.printstacktrace();
return "";
}
}
public String getDecryptedText(String cipherText) {
try {
// Splitting IV and Encrypted text
String iv = cipherText.substring(0,16);
System.out.println("IV : "+iv);
byte[] IV = Base64.getDecoder().decode(iv);
cipherText = cipherText.substring(16);
byte[] data = Base64.getDecoder().decode(cipherText);
return decrypt(data,IV);
} catch (Exception e) {
e.printstacktrace();
return "";
}
}
private SecretKeySpec getKeySpec() {
SecretKeySpec spec = null;
try {
byte[] bytes = new byte[32];
String pwd = "Test!ng012345678"; //Temporary
bytes = pwd.getBytes();
spec = new SecretKeySpec(bytes,"AES");
return spec;
} catch (Exception e) {
e.printstacktrace();
}
return spec;
}
private byte[] encrypt(byte[] plaintext,SecretKey key,byte[] IV) throws Exception {
// Get Cipher Instance
Cipher cipher = Cipher.getInstance("AES/GCM/nopadding");
// Create SecretKeySpec
SecretKeySpec keySpec = new SecretKeySpec(key.getEncoded(),"AES");
// Create GCMParameterSpec
GCMParameterSpec gcmParameterSpec = new GCMParameterSpec(GCM_TAG_LENGTH * 8,IV);
// Initialize Cipher for ENCRYPT_MODE
cipher.init(Cipher.ENCRYPT_MODE,keySpec,gcmParameterSpec);
// Perform Encryption
byte[] cipherText = cipher.doFinal(plaintext);
return cipherText;
}
private String decrypt(byte[] cipherText,IV);
// Initialize Cipher for DECRYPT_MODE
cipher.init(Cipher.DECRYPT_MODE,gcmParameterSpec);
// Perform Decryption
byte[] decryptedText = cipher.doFinal(cipherText);
return new String(decryptedText);
}
}
我的 Dart 代码
Future<String> decrypt(String textBlock) async {
Uint8List data = base64.decode("4NA09I5VpmdD0o1k3VP8eIfyZRKDtzOwgJv5nh0nmEPZ/Q==");
Uint8List passphrase = utf8.encode('Test!ng012345678');
SecretKey secretKey = new SecretKey(passphrase);
Uint8List iv = utf8.encode('/U0OI/AdHDM4QFVC');
SecretBox secretBox = new SecretBox(data,nonce: iv);
List<int> decrypted = await AesGcm.with128bits().decrypt(secretBox,secretKey: secretKey);
String dec = utf8.decode(decrypted);
print("DATA : "+dec);
return dec;
}
未处理的异常:SecretBox 的消息身份验证代码 (MAC) 错误 #0 DartAesGcm.decryptSync (package:cryptography/src/dart/aes_gcm.dart:112:7) #1 DartAesGcm.decrypt (package:cryptography/src/dart/aes_gcm.dart:58:12) #2 EncryptionHandler.decrypt (package:investment_app/encryption/encryption_handler.dart:45:27)
解决方法
Java 中的 SunJCE 提供程序连接密文和 MAC:ciphertext|MAC。在 Dart 代码中,两者必须分开指定,这在贴出的代码中是不会发生的。此外,IV 不是 Base64 解码的。
以下代码是修复错误的可能实现:
Uint8List ivCiphertextMac = base64.decode("/U0OI/AdHDM4QFVC4NA09I5VpmdD0o1k3VP8eIfyZRKDtzOwgJv5nh0nmEPZ/Q=="); // from the Java code
Uint8List iv = ivCiphertextMac.sublist(0,12);
Uint8List ciphertext = ivCiphertextMac.sublist(12,ivCiphertextMac.length - 16);
Uint8List mac = ivCiphertextMac.sublist(ivCiphertextMac.length - 16);
Uint8List passphrase = utf8.encode('Test!ng012345678');
SecretKey secretKey = new SecretKey(passphrase);
SecretBox secretBox = new SecretBox(ciphertext,nonce: iv,mac: new Mac(mac));
List<int> decrypted = await AesGcm.with128bits().decrypt(secretBox,secretKey: secretKey);
String dec = utf8.decode(decrypted);
print("Decrypted text : " + dec); // Decrypted text : Mayur,You got it!
解密给出:Mayur,你明白了!
实际上 SecretBox
提供了方法 fromConcatenation()
,它应该将 IV、密文和 MAC 的串联分开。但是这个实现似乎返回了一个损坏的密文,这可能是一个错误。
编辑:
关于您在评论中的问题:MAC 在加密过程中自动生成。下面的代码实现了加密,其中ivCiphertextMacB64
包含IV的Base64编码|密文|马克:
Uint8List plaintext = utf8.encode("Mayur,You got it!");
Uint8List iv = AesGcm.with128bits().newNonce();
Uint8List passphrase = utf8.encode('Test!ng012345678');
SecretKey secretKey = new SecretKey(passphrase);
SecretBox secretBox = await AesGcm.with128bits().encrypt(plaintext,secretKey: secretKey);
String ivCiphertextMacB64 = base64.encode(secretBox.concatenation()); // Base64 encoding of: IV | ciphertext | MAC
print("ivCiphertextMacB64 : " + ivCiphertextMacB64);
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