在 Android 中使用 AES/CBC/PKCS5Padding 解密不正确

我在 Android (v2.2 API 8) 中编写了以下代码，其中输入纯文本，代码使用用户密码和随机盐对其进行加密，然后解密。运行代码后，我只得到部分正确的纯文本。例如用户输入“Msg 1.5 to encrypt”，解密结果为“Msg15toencrypg==”

这是代码：

 private EditText plain_msg;
    private EditText pwd;
    private TextView result;
    byte[] iv;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    plain_msg = (EditText)findViewById(R.id.msg2encypt);
    pwd = (EditText)findViewById(R.id.password);
    result = (TextView)findViewById(R.id.decrypttxt);
}

public void mybuttonHandler(View view){
    String S_plain_msg = plain_msg.getText().toString();
    String S_pwd = pwd.getText().toString();
    setAES(S_plain_msg, S_pwd);
}


private byte[] generateSalt() throws NoSuchAlgorithmException{
    SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
    byte[] ransalt = new byte[20];
    random.nextBytes(ransalt);
    return ransalt;
}


private void setAES(String msg, String pwd){
    try {
        //Generation of Key
        byte[] salt = generateSalt();
        SecretKeyFactory factory = SecretKeyFactory.getInstance("PBEWITHSHA256AND256BITAES-CBC-BC");
        KeySpec spec = new PBEKeySpec(pwd.toCharArray(),salt,1024, 256);
        SecretKey tmp = factory.generateSecret(spec);
        SecretKey secret = new SecretKeySpec(tmp.getEncoded(), "AES");

        //Encryption process
        byte[] btxt = Base64.decode(msg, 0);
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, secret); 
        AlgorithmParameters params = cipher.getParameters(); 
        iv = params.getParameterSpec(IvParameterSpec.class).getIV(); 
        byte[] ciphertext = cipher.doFinal(btxt);
        String encryptedtext = Base64.encodeToString(ciphertext, 0);

        //Decryption process
        byte[] bencryptxt = Base64.decode(encryptedtext, 0);
        cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, secret, new IvParameterSpec(iv)); 
        ciphertext = cipher.doFinal(bencryptxt);
        String cipherS = Base64.encodeToString(ciphertext, 0); 

        result.setText(cipherS);
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    } catch (GeneralSecurityException e) {
        e.printStackTrace();
    } 

}

}

如果去掉加密解密，这应该是身份转换，剩下的是：

Base64.encodeToString(Base64.decode(msg))

"Msg 1.5 to encrypt"不是 Base64 编码的字符串，无需尝试对其进行解码。如果您这样做，就像您所做的那样，非 Base64 字符会被剥离，并且您会得到一些字节，这些字节在编码回来时看起来就像您得到的结果。