Android 字符串 Encryption/Decryption

Question

我想使用 AndroidKeyStore 从 EditText 加密和解密 String。我的问题是在解密过程中得到 BadPaddingException.

密钥生成器代码：

        KeyGenerator keyGenerator = KeyGenerator.getInstance(KeyProperties.KEY_ALGORITHM_AES, "AndroidKeyStore");

        KeyGenParameterSpec keyGenParameterSpec = new KeyGenParameterSpec.Builder(ALIAS, KeyProperties.PURPOSE_ENCRYPT | KeyProperties.PURPOSE_DECRYPT).
                setBlockModes(KeyProperties.BLOCK_MODE_GCM).setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE).build();

        keyGenerator.init(keyGenParameterSpec);
        keyGenerator.generateKey();

加密密码：

            KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
            keyStore.load(null);

            KeyStore.SecretKeyEntry secretKeyEntry = (KeyStore.SecretKeyEntry) keyStore.getEntry(ALIAS, null);
            SecretKey secretKey = secretKeyEntry.getSecretKey();

            Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
            cipher.init(Cipher.ENCRYPT_MODE, secretKey);

            cipherIV = cipher.getIV();

            plainText.setText(new String(cipher.doFinal(plainText.getText().toString().getBytes(StandardCharsets.UTF_8)), StandardCharsets.UTF_8));

解密密码：

            KeyStore keyStore = KeyStore.getInstance("AndroidKeyStore");
            keyStore.load(null);

            final KeyStore.SecretKeyEntry secretKeyEntry = (KeyStore.SecretKeyEntry) keyStore.getEntry(ALIAS, null);
            final SecretKey secretKey = secretKeyEntry.getSecretKey();

            final Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
            final GCMParameterSpec spec = new GCMParameterSpec(128, cipherIV);
            cipher.init(Cipher.DECRYPT_MODE, secretKey, spec);

            byte[] decrypted = cipher.doFinal(plainText.getText().toString().getBytes(StandardCharsets.UTF_8));
            plainText.setText(new String(decrypted, StandardCharsets.UTF_8));

Answer 1

byte[] decrypted = cipher.doFinal(plainText.getText().toString().getBytes(StandardCharsets.UTF_8));

由于getBytes(StandardCharsets.UTF_8)的调用，这条线路可能无法正常工作。如果您的 EditText 是十六进制表示，请尝试将其转换为字符串，然后调用 getBytes()。例如。

public static byte[] convertHexStringToByteArray(String hexString) {

    int l = hexString.length();
    byte[] data = new byte[l/2];
    for (int i = 0; i < l; i += 2) {
        data[i/2] = (byte)((Character.digit(hexString.charAt(i), 16) << 4) + Character.digit(hexString.charAt(i+1), 16));
    }

    return data;
}

Answer 2

这一行有误：

plainText.setText(new String(cipher.doFinal(plainText.getText().toString().getBytes(StandardCharsets.UTF_8)), StandardCharsets.UTF_8));

如果我们把它分开，我们有类似的东西

byte [] cipherBytes = cipher.doFinal(plainText.getText().toString().getBytes(StandardCharsets.UTF_8));
plainText.setText(new String(cipherBytes, StandardCharsets.UTF_8);

问题是 cipherBytes 是一个任意字节的序列，而不是字符串的字符。 String 构造函数会悄悄地用其他东西替换无效字符，这是一个破坏数据的过程。

如果您想显示密码字节或以其他方式将其发送到面向字符的频道，您必须对它进行编码。通常编码是 base64 或十六进制。要解密字符串，您必须先将其解码为字节，然后再解密。

示例：

byte [] cipherBytes = cipher.doFinal(plainText.getText().toString().getBytes(StandardCharsets.UTF_8));
plainText.setText(Base64.encodeToString(cipherBytes, Base64.DEFAULT));

解密时：

byte[] cipherBytes = Base64.decode(plainText.getText().toString(), Base64.DEFAULT);
byte[] decrypted = cipher.doFinal(cipherBytes);

Android 字符串 Encryption/Decryption

Android String Encryption/Decryption

java

android

encryption

android-keystore