6

以下のコードは機能しますが、継続的に実行すると、「最後のブロックが適切にパディングされていません」とスローされる場合があります。どこかでちょっとしたミスをしている気がします。問題の解決を手伝ってもらえますか？

例外スタック：

Exception in thread "main" javax.crypto.BadPaddingException: Given final block not properly padded
    at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:811)
    at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:676)
    at com.sun.crypto.provider.AESCipher.engineDoFinal(AESCipher.java:313)
    at javax.crypto.Cipher.doFinal(Cipher.java:2086)
    at MCrypt.decrypt(MCrypt.java:87)
    at MCrypt.main(MCrypt.java:21)

そして私のコード：

import java.security.SecureRandom;
import java.security.spec.KeySpec;

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;

public class MCrypt {

    private int iterationCount = 10000;
    private int saltLength = 8; // bytes; 64 bits
    private int keyLength = 128;

    public static void main(String[] args) throws Exception {
        MCrypt mc = new MCrypt();
        String encryptedData = mc.encrypt("1234");
        MCrypt mc1 = new MCrypt();
        System.out.println(new String(mc1.decrypt(new String(encryptedData),
                "1234"), "UTF-8"));
    }

    public MCrypt() {
    }

    public String encrypt(String text) throws Exception {
        if (text == null || text.length() == 0)
            throw new Exception("Empty string");

        byte[] encrypted = null;

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

        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");

        byte[] iv = new byte[cipher.getBlockSize()];
        random.nextBytes(iv);
        IvParameterSpec ivParams = new IvParameterSpec(iv);

        KeySpec keySpec = new PBEKeySpec(text.toCharArray(), salt,
                iterationCount, keyLength);
        SecretKeyFactory keyFactory = SecretKeyFactory
                .getInstance("PBKDF2WithHmacSHA1");
        byte[] keyBytes = keyFactory.generateSecret(keySpec).getEncoded();
        SecretKey key = new SecretKeySpec(keyBytes, "AES");

        cipher.init(Cipher.ENCRYPT_MODE, key, ivParams);

        encrypted = cipher.doFinal(text.getBytes("UTF-8"));
        String encryptedStr = Base64.encodeBytes(encrypted);

        StringBuffer strBuf = new StringBuffer();
        strBuf.append(new String(encryptedStr));
        strBuf.append("]");
        strBuf.append(new String(salt));
        strBuf.append("]");
        strBuf.append(new String(iv));

        return new String(Base64.encodeBytes(strBuf.toString().getBytes()));
    }

    public byte[] decrypt(String code, String pwd) throws Exception {
        if (code == null || code.length() == 0)
            throw new Exception("Empty string");

        String[] fields = new String(Base64.decode(code)).split("]");
        byte[] cipherBytes = Base64.decode(fields[0]);
        byte[] salt = fields[1].getBytes();
        byte[] iv = fields[2].getBytes();

        KeySpec keySpec = new PBEKeySpec(pwd.toCharArray(), salt,
                iterationCount, keyLength);
        SecretKeyFactory keyFactory = SecretKeyFactory
                .getInstance("PBKDF2WithHmacSHA1");
        byte[] keyBytes = keyFactory.generateSecret(keySpec).getEncoded();
        SecretKey key = new SecretKeySpec(keyBytes, "AES");

        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        IvParameterSpec ivParams = new IvParameterSpec(iv);

        byte[] decrypted = null;
        cipher.init(Cipher.DECRYPT_MODE, key, ivParams);
        decrypted = cipher.doFinal(cipherBytes);

        return decrypted;
    }

}
4

1 に答える 1

0

これを見て

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

import android.util.Base64;
import android.util.Log;

public class AesFileIo {
//    private static final String AES_ALGORITHM = "AES/CTR/NoPadding";
    private static final String AES_ALGORITHM = "AES/CBC/PKCS5Padding";
    private SecretKeySpec secretKeySpec;
    private IvParameterSpec ivSpec;

    public AesFileIo(byte[] aesKey, byte[] iv) {
        ivSpec = new IvParameterSpec(iv);
        secretKeySpec = new SecretKeySpec(aesKey, "AES");
    }

    public String decrypt(String text) {

        StringBuilder stringBuilder = new StringBuilder(); 
        try {
            Cipher cipher = Cipher.getInstance(AES_ALGORITHM);
            cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, ivSpec);
            byte[] decordedValue =  Base64.decode(text,Base64.DEFAULT);
            String decryptedValue = new String(cipher.doFinal(decordedValue),"UTF-8");
            Log.e("decrypted Value :",decryptedValue);
            return decryptedValue; 
        } catch (Exception e) {
            Log.e(this.getClass().toString(), e.getMessage(), e);
        }
        return stringBuilder.toString();
    }

    public String encrypt(String text) {
        String encryptedValue=null;
        try {
            Cipher cipher = Cipher.getInstance(AES_ALGORITHM); 
            cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivSpec);
            byte[] encValue = cipher.doFinal(text.getBytes());
            encryptedValue = Base64.encodeToString(encValue,Base64.DEFAULT);
        } catch (Exception e) {
            Log.e(this.getClass().toString(), e.getMessage(), e);
        }
        return encryptedValue;
    }
}

使い方

public static byte[] iv = { '0', '0','0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0' };
    private static final byte[] keyValue = new byte[] { 'b', 'i', 'r', 'a', 'j', 'z', 'a', 'l', 'a', 'v', 'a', 'd', 'i', 'y', 'a', 'r' };
AesFileIo aes = new AesFileIo(keyValue, iv);
String encrypetedText = aes.encrypt(str);
String decryptedText = aes.decrypt(encrypetedText);

System.out.println("EncrypetedText : " + encrypetedText);
System.out.println("DecryptedText : " + decryptedText);
于 2013-09-17T11:17:32.500 に答える