AES加密badPadding

Question

尝试解密NFC标签（其中包含与生成的QR码完全相同的值.QRCode能够正确扫描而没有任何错误。虽然包含完全相同值的NFC标签正在抛出BadPaddingException。

String seedValue = "MediLearnerSecurity";
encyrptedResult = "4EA768CA389F4CD688BCCAF11E1E4953"

从标签和条形码扫描仪检查和检索后。两者都被验证包含上述encyrptedResult。

其他一些课程

public void decyrption()
{
  try
  {
    deCryptedResult = AESHelper.decrypt(seedValue, encyrptedResult);
  }
  catch (Exception e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
  }
}

AESHelper Class。

 public class AESHelper {

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

        public static String decrypt(String seed, String encrypted) throws Exception {
                byte[] rawKey = getRawKey(seed.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 final static String HEX = "0123456789ABCDEF";
        private static void appendHex(StringBuffer sb, byte b) {
                sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
        }


    }

logcat的

01-21 15:44:25.774: D/TextLayoutCache(11831): Enable myanmar Zawgyi converter
01-21 15:44:31.269: W/System.err(11831): javax.crypto.BadPaddingException: pad block corrupted
01-21 15:44:31.269: W/System.err(11831):    at com.android.org.bouncycastle.jcajce.provider.symmetric.util.BaseBlockCipher.engineDoFinal(BaseBlockCipher.java:710)
01-21 15:44:31.269: W/System.err(11831):    at javax.crypto.Cipher.doFinal(Cipher.java:1111)
01-21 15:44:31.269: W/System.err(11831):    at nyp.medilearner.methods.AESHelper.decrypt(AESHelper.java:48)
01-21 15:44:31.269: W/System.err(11831):    at nyp.medilearner.methods.AESHelper.decrypt(AESHelper.java:21)
01-21 15:44:31.269: W/System.err(11831):    at com.medilearner.main.ScanSelected.decyrption(ScanSelected.java:148)
01-21 15:44:31.269: W/System.err(11831):    at com.medilearner.main.ScanSelected.onActivityResult(ScanSelected.java:42)
01-21 15:44:31.269: W/System.err(11831):    at android.app.Activity.dispatchActivityResult(Activity.java:5563)
01-21 15:44:31.269: W/System.err(11831):    at android.app.ActivityThread.deliverResults(ActivityThread.java:3496)
01-21 15:44:31.274: W/System.err(11831):    at android.app.ActivityThread.handleSendResult(ActivityThread.java:3543)
01-21 15:44:31.274: W/System.err(11831):    at android.app.ActivityThread.access$1200(ActivityThread.java:159)
01-21 15:44:31.274: W/System.err(11831):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1364)
01-21 15:44:31.274: W/System.err(11831):    at android.os.Handler.dispatchMessage(Handler.java:99)
01-21 15:44:31.274: W/System.err(11831):    at android.os.Looper.loop(Looper.java:137)
01-21 15:44:31.274: W/System.err(11831):    at android.app.ActivityThread.main(ActivityThread.java:5419)
01-21 15:44:31.274: W/System.err(11831):    at java.lang.reflect.Method.invokeNative(Native Method)
01-21 15:44:31.274: W/System.err(11831):    at java.lang.reflect.Method.invoke(Method.java:525)
01-21 15:44:31.274: W/System.err(11831):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1209)
01-21 15:44:31.279: W/System.err(11831):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1025)
01-21 15:44:31.279: W/System.err(11831):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

我认为您的一个问题位于byte[] getRawKey(byte[] seed)。

如果我理解正确，这种方法假定您总是获得给定种子的相同密钥。

然而事实并非如此，因为它使用SHA1PRNG - 并且此类伪随机生成器未标准化。因此，如果您只使用Java SE 1.6生成密钥，您将始终获得相同的结果。但是其他编程语言中的SHA1PRNG算法，Android等替代Java平台甚至其他Java版本/库我得到的结果都不同。

另请阅读：javax.crypto working differently in different versions of Android OS?

结论：永远不要滥用KeyGenerator和/或SecureRandom来创建密钥。这些类的唯一用法是创建新的随机密钥！ 您发布的当前实施完全失败。