如果它只是将密钥存储在SharedPreferences中，Facebook Conceal如何安全？

Question

我希望保护一些存储在SharedPreferences中的用户数据，因此我查看了Facebook Conceal。

存储在SharedPreferences中的固有问题是有方法可以访问它并查看数据，所以很自然会想到加密它以便查看它是没有用的，但如果{{1还将密钥存储在Facebook Conceal中它是如何安全的？看起来在这种情况下查看数据现在只需要两个额外的步骤 - 获取密钥并使用它来解密数据。

我想我在这里遗漏了一些东西，所以我只是在寻找澄清为什么SharedPreferences是安全的，如果它将用于解密数据的密钥存储在数据的同一个地方首先是不安全的。

Answer 1

共享Prefs可以是公共的也可以是私有的。但这意味着分配给xml文件的安全组存储了键/值对及其位置。

如果您想要安全的东西，可以使用SecureSharedPreference实现。这样可以确保没有人可以窃取您的信息（从来都不是超级黑客的保证哈哈）但是这就像偷一个外语并且好好破解它。

但是，如果您想确保它没有被盗并且没有被触及，那么使用本地数据库会更好。这也很容易受到有才华的黑客的影响，所以你可以使用SQLCipher来确保它在数据库中加密以及私下存储为你的应用程序。

因此，您的架构和安全需求取决于您以及您的安全团队可接受的内容。这是一个开源的securePref文件，我用于需要安全存储和访问的数据，但如果有人窃取我的笨拙混乱，因为他们无法对它做任何事情，这不是世界末日。

 /*
Copyright (C) 2012 Sveinung Kval Bakken, sveinung.bakken@gmail.com
Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

import android.content.Context;
import android.content.SharedPreferences;
import android.util.Base64;

import java.io.UnsupportedEncodingException;
import java.security.GeneralSecurityException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;


public class SecuredPreferences {

    public static class SecurePreferencesException extends RuntimeException {

        public SecurePreferencesException(Throwable e) {
            super(e);
        }

    }

        private static final String TRANSFORMATION = "AES/CBC/PKCS5Padding";
        private static final String KEY_TRANSFORMATION = "AES/ECB/PKCS5Padding";
        private static final String SECRET_KEY_HASH_TRANSFORMATION = "SHA-256";
        private static final String CHARSET = "UTF-8";

        private final boolean encryptKeys;
        private final Cipher writer;
        private final Cipher reader;
        private final Cipher keyW

riter;
    private final SharedPreferences preferences;

    /**
     * This will initialize an instance of the SecurePreferences class
     * @param context your current context.
     * @param preferenceName name of preferences file (preferenceName.xml)
     * @param secureKey the key used for encryption, finding a good key scheme is hard.
     * Hardcoding your key in the application is bad, but better than plaintext preferences. Having the user enter the key upon application launch is a safe(r) alternative, but annoying to the user.
     * @param encryptKeys settings this to false will only encrypt the values,
     * true will encrypt both values and keys. Keys can contain a lot of information about
     * the plaintext value of the value which can be used to decipher the value.
     * @throws SecurePreferencesException
     */
    public SecuredPreferences(Context context, String preferenceName, String secureKey, boolean encryptKeys) throws SecurePreferencesException {
        try {
            this.writer = Cipher.getInstance(TRANSFORMATION);
            this.reader = Cipher.getInstance(TRANSFORMATION);
            this.keyWriter = Cipher.getInstance(KEY_TRANSFORMATION);

            initCiphers(secureKey);

            this.preferences = context.getSharedPreferences(preferenceName, Context.MODE_PRIVATE);

            this.encryptKeys = encryptKeys;
        }
        catch (GeneralSecurityException e) {
            throw new SecurePreferencesException(e);
        }
        catch (UnsupportedEncodingException e) {
            throw new SecurePreferencesException(e);
        }
    }

    protected void initCiphers(String secureKey) throws UnsupportedEncodingException, NoSuchAlgorithmException, InvalidKeyException,
            InvalidAlgorithmParameterException {
        IvParameterSpec ivSpec = getIv();
        SecretKeySpec secretKey = getSecretKey(secureKey);

        writer.init(Cipher.ENCRYPT_MODE, secretKey, ivSpec);
        reader.init(Cipher.DECRYPT_MODE, secretKey, ivSpec);
        keyWriter.init(Cipher.ENCRYPT_MODE, secretKey);
    }

    protected IvParameterSpec getIv() {
        byte[] iv = new byte[writer.getBlockSize()];
        System.arraycopy("fldsjfodasjifudslfjdsaofshaufihadsf".getBytes(), 0, iv, 0, writer.getBlockSize());
        return new IvParameterSpec(iv);
    }

    protected SecretKeySpec getSecretKey(String key) throws UnsupportedEncodingException, NoSuchAlgorithmException {
        byte[] keyBytes = createKeyBytes(key);
        return new SecretKeySpec(keyBytes, TRANSFORMATION);
    }

    protected byte[] createKeyBytes(String key) throws UnsupportedEncodingException, NoSuchAlgorithmException {
        MessageDigest md = MessageDigest.getInstance(SECRET_KEY_HASH_TRANSFORMATION);
        md.reset();
        byte[] keyBytes = md.digest(key.getBytes(CHARSET));
        return keyBytes;
    }

    public void put(String key, String value) {
        if (value == null) {
            preferences.edit().remove(toKey(key)).commit();
        }
        else {
            putValue(toKey(key), value);
        }
    }

    public boolean containsKey(String key) {
        return preferences.contains(toKey(key));
    }

    public void removeValue(String key) {
        preferences.edit().remove(toKey(key)).commit();
    }

public String getString(String key) throws SecurePreferencesException {
    if (preferences.contains(toKey(key))) {
        String securedEncodedValue = preferences.getString(toKey(key), "");
        return decrypt(securedEncodedValue);
    }
    return null;
}

public void clear() {
    preferences.edit().clear().commit();
}

private String toKey(String key) {
    if (encryptKeys)
        return encrypt(key, keyWriter);
    else return key;
}

private void putValue(String key, String value) throws SecurePreferencesException {
    String secureValueEncoded = encrypt(value, writer);

    preferences.edit().putString(key, secureValueEncoded).commit();
}

protected String encrypt(String value, Cipher writer) throws SecurePreferencesException {
    byte[] secureValue;
    try {
        secureValue = convert(writer, value.getBytes(CHARSET));
    }
    catch (UnsupportedEncodingException e) {
        throw new SecurePreferencesException(e);
    }
    String secureValueEncoded = Base64.encodeToString(secureValue, Base64.NO_WRAP);
    return secureValueEncoded;
}

protected String decrypt(String securedEncodedValue) {
    byte[] securedValue = Base64.decode(securedEncodedValue, Base64.NO_WRAP);
    byte[] value = convert(reader, securedValue);
    try {
        return new String(value, CHARSET);
    }
    catch (UnsupportedEncodingException e) {
        throw new SecurePreferencesException(e);
    }
}

private static byte[] convert(Cipher cipher, byte[] bs) throws SecurePreferencesException {
    try {
            return cipher.doFinal(bs);
        }
        catch (Exception e) {
            throw new SecurePreferencesException(e);
        }
    }
}

希望这会有所帮助。对于安全密钥，只需制作自己的随机盐，但要保持固定，以免变化。