主页 / 问题 / 621938
Accepted
Evgeniy
Asked:2020-02-01 05:51:02 +0000 UTC2020-02-01 05:51:02 +0000 UTC

AES：未解密的字符串

  • 772

我有两个功能，encrypt和decrypt。在encrypt我创建一个密钥，加密一个字符串，并将密钥本身添加到字符串的开头。首先，我从加密字符串中分离出decrypt密钥（密钥大小是固定的）并尝试解密，但结果与初始字符串不匹配，这就是问题所在。

检查调试，在两个函数中key调用时数组是相同decrypt(encrypt(string))的，显然问题出在SecretKeySpec（恕我直言）。

我该如何解决？

代码本身：

static String encrypt(String str) {
    SecretKeySpec sks = null;
    byte[] key = null;
    try {
        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
        sr.setSeed("this is seed".getBytes());
        KeyGenerator kg = KeyGenerator.getInstance("AES");
        kg.init(128, sr);
        key = kg.generateKey().getEncoded();
        sks = new SecretKeySpec(key, "AES");
    } catch (Exception e) {
        Log.e("Crypto", "AES secret key spec error");
    }

    // Encode the original data with AES
    byte[] encodedBytes = null;
    try {
        Cipher c = Cipher.getInstance("AES");
        c.init(Cipher.ENCRYPT_MODE, sks);
        encodedBytes = c.doFinal(str.getBytes());
    } catch (Exception e) {
        Log.e("Crypto", "AES encryption error");
    }

    return Base64.encodeToString(key, Base64.DEFAULT) + 
        Base64.encodeToString(encodedBytes, Base64.DEFAULT);
}

static String decrypt(String str) {

    byte[] key = Base64.decode(str.substring(0, 25), Base64.DEFAULT);

    byte[] strBytes =
        Base64.decode(str.substring(25, str.length()), Base64.DEFAULT);

    SecretKeySpec sks = new SecretKeySpec(key, "AES");

    // Decode the encoded data with AES
    byte[] decodedBytes = null;
    try {
        Cipher c = Cipher.getInstance("AES");
        c.init(Cipher.DECRYPT_MODE, sks);
        decodedBytes = c.doFinal(strBytes);
    } catch (Exception e) {
        Log.e("Crypto", "AES decryption error");
    }

    return Base64.encodeToString(decodedBytes, Base64.DEFAULT);
}

UPD调用方法：

editText.setText(Crypt.encrypt(editText.getText().toString()));
...
editText.setText(Crypt.decrypt(editText.getText().toString()));
java

1 个回答

  1. Best Answer

    您遇到的问题不在密钥中，而在返回字符串时的额外编码中。

    在 JVM 上调试此类代码的最简单方法是使用测试。

    // этот тест для обычного JUnit
// я не пробовал запускать его на андроиде
@Test
public void encrypt() throws Exception {
    String cryptoText = AES.encrypt("test");
    String plainText = AES.decrypt(cryptoText);
    assertThat(plainText, is("test"));
}

static String encrypt(String str) {
    SecretKeySpec sks = null;
    byte[] key = null;
    try {
        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
        sr.setSeed("this is seed".getBytes());
        KeyGenerator kg = KeyGenerator.getInstance("AES");
        kg.init(128, sr);
        key = kg.generateKey().getEncoded();
        sks = new SecretKeySpec(key, "AES");
    } catch (Exception e) {
        Log.e("Crypto", "AES secret key spec error");
    }

    // Encode the original data with AES
    byte[] encodedBytes = null;
    try {
        Cipher c = Cipher.getInstance("AES");
        c.init(Cipher.ENCRYPT_MODE, sks);
        encodedBytes = c.doFinal(str.getBytes());
    } catch (Exception e) {
        Log.e("Crypto", "AES encryption error");
    }
    // я добавил длину ключа и разделитель
    String encodeKey = Base64.encodeToString(key, Base64.DEFAULT);
    return encodeKey.length() + "$" + encodeKey +
        Base64.encodeToString(encodedBytes, Base64.DEFAULT);        
}

static String decrypt(String str) {

    int pos = str.indexOf("$");
    int keyLength = Integer.valueOf(str.substring(0, pos));
    int keyStart = pos + 1;

    byte[] key = Base64.decode(str.substring(keyStart, keyStart + keyLength), Base64.DEFAULT);

    int dataStart = keyStart + keyLength;
    byte[] strBytes =
        Base64.decode(str.substring(dataStart, str.length()), Base64.DEFAULT);

    SecretKeySpec sks = new SecretKeySpec(key, "AES");

    // Decode the encoded data with AES
    byte[] decodedBytes = null;
    try {
        Cipher c = Cipher.getInstance("AES");
        c.init(Cipher.DECRYPT_MODE, sks);
        decodedBytes = c.doFinal(strBytes);
    } catch (Exception e) {
        Log.e("Crypto", "AES decryption error");
    }

    // Base64 не надо, так как у вас там просто строка
    // return Base64.encodeToString(decodedBytes, Base64.DEFAULT);
    return new String(decodedBytes);
}
    • 2

相关问题