Android AES Decrypt decryptBytes(String seed, byte[] encrypted)

Description

decrypt Bytes

Declaration

public static byte[] decryptBytes(String seed, byte[] encrypted)
            throws Exception 

Method Source Code

//package com.java2s;
import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import android.util.Base64;

public class Main {
    private final static int JELLY_BEAN_4_2 = 17;
    private final static byte[] key = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0 };//from  w  w  w  . j a v  a 2 s . co m
    private final static String theRawKey = "7834uwerqwerqwerqwerqwerqwerdfu823jhwef80";

    public static byte[] decryptBytes(String seed, byte[] encrypted)
            throws Exception {
        byte[] rawKey = getRawKey(seed.getBytes());
        byte[] result = decrypt(rawKey, encrypted);
        return result;
    }

    private static byte[] getRawKey(byte[] seed) throws Exception {
        KeyGenerator kgen = KeyGenerator.getInstance("AES"); // , "SC");
        SecureRandom sr = null;
        if (android.os.Build.VERSION.SDK_INT >= JELLY_BEAN_4_2) {
            sr = SecureRandom.getInstance("SHA1PRNG", "Crypto");
        } else {
            sr = SecureRandom.getInstance("SHA1PRNG");
        }
        sr.setSeed(seed);
        try {
            kgen.init(256, sr);
            // kgen.init(128, sr);
        } catch (Exception e) {
            // Log.w(LOG,
            // "This device doesn't suppor 256bits, trying 192bits.");
            try {
                kgen.init(192, sr);
            } catch (Exception e1) {
                // Log.w(LOG,
                // "This device doesn't suppor 192bits, trying 128bits.");
                kgen.init(128, sr);
            }
        }
        SecretKey skey = kgen.generateKey();
        byte[] raw = skey.getEncoded();
        return raw;
    }

    public static String decrypt(String encrypted) throws Exception {
        byte[] seedByte = theRawKey.getBytes();
        System.arraycopy(seedByte, 0, key, 0,
                ((seedByte.length < 16) ? seedByte.length : 16));
        String base64 = new String(Base64.decode(encrypted, 0));
        byte[] rawKey = getRawKey(seedByte);
        byte[] enc = toByte(base64);
        byte[] result = decrypt(rawKey, enc);
        return new String(result);
    }

    private static byte[] decrypt(byte[] raw, byte[] encrypted)
            throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
        Cipher cipher = Cipher.getInstance("AES"); // /ECB/PKCS7Padding", "SC");
        cipher.init(Cipher.DECRYPT_MODE, skeySpec);
        byte[] decrypted = cipher.doFinal(encrypted);
        return decrypted;
    }

    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;
    }
}

Related

1. decrypt(byte[] textBytes, String key)
2. decryptBase64(String content, String key)
3. decryptBase64(String encryptBase64)
4. decryptBase64Text(String key, String src)
5. decryptBytes(String key, byte[] src)
6. decryptBytes(byte[] data, byte[] key)
7. decryptHex(String content, String key)
8. decryptHex(String content, String username, String password)
9. decryptNumberWithAES(String encrypted)