Question

我有一个应用程序可以加密一些文本字符串，然后将这些文本字符串写入文件。应用程序的桌面版本正在读取文件并解密数据。问题是，无论何时我在桌面版本上解密，我都会得到一个＆＃34; javax.crypto.BadPaddingException：给定最终块未正确填充＆＃34;

应用和桌面都使用相同的代码：

import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

public class SSL {

    private final static String HEX = "0123456789ABCDEF";

    public static String encrypt(Session current, String cleartext) throws Exception {
        byte[] rawKey = getRawKey(current.getCurrentSession().getBytes());
        byte[] result = encrypt(rawKey, cleartext.getBytes());
        return toHex(result);
    }

    public static String decrypt(Session current, String encrypted) throws Exception {
        byte[] rawKey = getRawKey(current.getCurrentSession().getBytes());
        byte[] enc = toByte(encrypted);     
        byte[] result = decrypt(rawKey, enc);
        return new String(result);
    }

    private static byte[] getRawKey(byte[] seed) throws Exception {
        KeyGenerator kgen = KeyGenerator.getInstance("AES");
        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
        sr.setSeed(seed);
        kgen.init(128, sr); // 192 and 256 bits may not be available
        SecretKey skey = kgen.generateKey();
        byte[] raw = skey.getEncoded();
        return raw;
    }


    private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
        byte[] encrypted = cipher.doFinal(clear);
        return encrypted;
    }

    private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.DECRYPT_MODE, skeySpec);
        byte[] decrypted = cipher.doFinal(encrypted);
        return decrypted;
    }

    public static String toHex(String txt) {
        return toHex(txt.getBytes());
    }
    public static String fromHex(String hex) {
        return new String(toByte(hex));
    }

    public static byte[] toByte(String hexString) {
        int len = hexString.length()/2;
        byte[] result = new byte[len];
        for (int i = 0; i < len; i++)
            result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
        return result;
    }

    public static String toHex(byte[] buf) {
        if (buf == null)
            return "";
        StringBuffer result = new StringBuffer(2*buf.length);
        for (int i = 0; i < buf.length; i++) {
            appendHex(result, buf[i]);
        }
        return result.toString();
    }

    private static void appendHex(StringBuffer sb, byte b) {
        sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
    }
}

为什么我无法解密桌面版的数据？ Android SDK和java 1.7中的加密实现是否有所不同？

注意：如果我在android上解密加密的android数据，它就可以了。如果我在桌面上加密和解密，它也可以。问题似乎介于这两者之间。

Answer 1

我终于找到了整个解决方案。

有一些重大问题，我想在此解释一下，以便更多用户可以找到答案。首先，Duncan指出的两件事需要修复。

在解决了这些问题后，我仍然遇到了同样的问题，并发现使用伪随机数创建原始密钥的方式不同，不同的平台/操作系统也是如此。如果您想拥有跨平台独立性，请不要使用SHA1PRNG作为关键算法。相反，使用PBEWithSHA256And256BitAES-CBC-BC。我正在使用BouncyCastle的实现，请参阅下面的完整加密代码。

import java.io.UnsupportedEncodingException;
import java.security.Security;
import java.security.spec.KeySpec;
import java.util.Random;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;

import org.bouncycastle.jce.provider.BouncyCastleProvider;

public class SSL {

    private final static String HEX = "0123456789ABCDEF";
    private final static String ENC = "US-ASCII";
    private final static int ITERATION = 1337;

    private static final String RANDOM_ALGORITHM = "PBEWithSHA256And256BitAES-CBC-BC";
    private static final String CIPHER_ALGORITHM = "AES/CBC/PKCS5Padding";
    private static final String SECRET_KEY_ALGORITHM = "AES";

    private static IvParameterSpec ips;

    public static void init(byte[] iv) {
        if(iv == null) {
            iv = new byte[16];

            Random random = new Random();
            random.nextBytes(iv);
        }

        ips = new IvParameterSpec(iv);

        Security.addProvider(new BouncyCastleProvider());
    }

    public static byte[] getCertificate() {
        return ips.getIV();
    }

    public static String encrypt(Session current, String cleartext) throws Exception {
        byte[] rawKey = getRawKey(current.getCurrentSession().toCharArray());
        byte[] result = encrypt(rawKey, cleartext.getBytes(ENC));
        return toHex(result);
    }

    public static String decrypt(Session current, String encrypted) throws Exception {
        byte[] rawKey = getRawKey(current.getCurrentSession().toCharArray());
        byte[] enc = toByte(encrypted);     
        byte[] result = decrypt(rawKey, enc);
        return new String(result, ENC);
    }

    private static byte[] getRawKey(char[] seed) throws Exception {
        KeySpec keySpec = new PBEKeySpec(seed, ips.getIV(), ITERATION);

        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(RANDOM_ALGORITHM);
        byte[] keyBytes = keyFactory.generateSecret(keySpec).getEncoded();
        SecretKey secretKey = new SecretKeySpec(keyBytes, "AES");

        return secretKey.getEncoded();
    }


    private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(raw, SECRET_KEY_ALGORITHM);
        Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec, ips);
        byte[] encrypted = cipher.doFinal(clear);
        return encrypted;
    }

    private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(raw, SECRET_KEY_ALGORITHM);
        Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, skeySpec, ips);
        byte[] decrypted = cipher.doFinal(encrypted);
        return decrypted;
    }

    public static String toHex(String txt) throws UnsupportedEncodingException {
        return toHex(txt.getBytes(ENC));
    }
    public static String fromHex(String hex) throws UnsupportedEncodingException {
        return new String(toByte(hex), ENC);
    }

    public static byte[] toByte(String hexString) {
        int len = hexString.length()/2;
        byte[] result = new byte[len];
        for (int i = 0; i < len; i++)
            result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
        return result;
    }

    public static String toHex(byte[] buf) {
        if (buf == null)
            return "";
        StringBuffer result = new StringBuffer(2*buf.length);
        for (int i = 0; i < buf.length; i++) {
            appendHex(result, buf[i]);
        }
        return result.toString();
    }

    private static void appendHex(StringBuffer sb, byte b) {
        sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
    }
}

Answer 2

您的代码至少有两个问题会影响其在不同平台上的功能：

您必须在致电getBytes()或new String(...)时指定字符集。如果没有这个，如果您的平台具有不同的默认字符集，结果将会不同。
您必须完全指定加密算法，例如将"AES"替换为"AES/CBC/PKCS5Padding"以避免提供商之间存在差异。

解密在android上加密的桌面上的数据

2 个答案: