这是一种安全的加密方法吗？

Question

我正在编写一款应用程序，使用对称密钥加密来保护敏感数据。据我所知，Android仅直接支持“PBEWithMD5AndDES”。这个算法有多安全？此外，我在下面包含了我的代码（非Android）。我的代码是否正确加密了数据？

import java.io.UnsupportedEncodingException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.InvalidParameterSpecException;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;

public class CipherTest
{

    private static class EncryptInfo
    {

        private final byte[] encryptedData;
        private final byte[] initVector;
        private final byte[] salt;

        public EncryptInfo(byte[] encryptedData, byte[] initVector, byte[] salt)
        {
            this.encryptedData = encryptedData.clone();
            this.initVector = initVector.clone();
            this.salt = salt.clone();
        }

        public byte[] getEncryptedData()
        {
            return encryptedData;
        }

        public byte[] getInitVector()
        {
            return initVector;
        }

        public byte[] getSalt()
        {
            return salt;
        }

    }

    private static final String keyGenAlgorithm = "PBEWithMD5AndDES";
    private static final String keyAlgorithm = "DES";
    private static final String cipherTransform = "PBEWithMD5AndDES/CBC/PKCS5Padding";

    private static EncryptInfo encrypt(char[] password, byte[] data)
            throws NoSuchAlgorithmException, InvalidKeySpecException,
            NoSuchPaddingException, InvalidKeyException,
            InvalidParameterSpecException, IllegalBlockSizeException,
            BadPaddingException, UnsupportedEncodingException
    {

        byte[] salt = new byte[16];
        new SecureRandom().nextBytes(salt);

        PBEKeySpec keySpec = new PBEKeySpec(password, salt, 1024);

        SecretKeyFactory secretKeyFactory = SecretKeyFactory
                .getInstance(keyGenAlgorithm);
        SecretKey secretKey = secretKeyFactory.generateSecret(keySpec);
        keySpec.clearPassword();
        byte[] key = secretKey.getEncoded();
        SecretKeySpec secretKeySpec = new SecretKeySpec(key, keyAlgorithm);
        Cipher cipher = Cipher.getInstance(cipherTransform);
        cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);

        byte[] initVector = cipher.getParameters().getParameterSpec(
                IvParameterSpec.class).getIV();

        return new EncryptInfo(cipher.doFinal(data), initVector, salt);
    }

    public static byte[] decrypt(byte[] data, char[] password, byte[] salt,
            byte[] initVector) throws NoSuchAlgorithmException,
            InvalidKeySpecException, NoSuchPaddingException,
            InvalidKeyException, InvalidAlgorithmParameterException,
            IllegalBlockSizeException, BadPaddingException
    {
        PBEKeySpec keySpec = new PBEKeySpec(password, salt, 1024);

        SecretKeyFactory secretKeyFactory = SecretKeyFactory
                .getInstance(keyGenAlgorithm);
        SecretKey secretKey = secretKeyFactory.generateSecret(keySpec);
        keySpec.clearPassword();
        byte[] key = secretKey.getEncoded();
        SecretKeySpec secretKeySpec = new SecretKeySpec(key, keyAlgorithm);
        Cipher cipher = Cipher.getInstance(cipherTransform);
        cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, new IvParameterSpec(
                initVector));
        return cipher.doFinal(data);
    }

    public static void main(String[] args) throws Exception
    {
        char[] password = "password".toCharArray();

        EncryptInfo info = encrypt(password, "Message".getBytes());

        byte[] decyptedText = decrypt(info.getEncryptedData(), password, info
                .getSalt(), info.getInitVector());

        System.out.println(new String(decyptedText));

    }
}

- Peter Sutton

---

“我的代码是否正确加密数据？”- 很抱歉，我们不会为您测试代码！您有一个加密和解密方法。尝试使用多个字符串运行一些简单的加密/解密测试。如果结果等于输入，则一切正常！ - WarrenFaith

Answer 1

MD5和DES都是不安全的。如果您要加密的数据真的很有价值，那么您应该寻找一些为Android提供AES和SHA256/SHA512算法的外部加密库。

- Eugene Mayevski 'Callback

Answer 2

如果您想使用对称密钥加密来加密数据, 我建议：
1) 使用AES，因为它已被NSA认证为机密级别的数据加密标准
2) 使用经过良好评价的实现，这样就不必研究如何配置代码。例如，使用AESCrypt。
您可以在此处找到AESCrypt: http://www.aescrypt.com/java_aes_crypt.html
我曾看到AESCrypt在多个金融机构中使用。Java版的AESCrypt是调用JCE方法的单个类。在Android中，JCE由bouncycastle实现。我也看到bouncycastle在一些重要的金融机构中使用。

- Mike