Android AES Decrypt decrypt(String encrypted)

Description

decrypt

Declaration

public static String decrypt(String 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 };/* w  w  w  .  j av  a 2  s  .  com*/
    private final static String theRawKey = "7834uyqwerqwerqwerqwerqwerqwerq823jhwef80";

    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;
    }

    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 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(String content, String password)
2. decrypt(String data)
3. decrypt(String dataPassword, String encrypted)
4. decrypt(String key, String encrypted)
5. decrypt(String key, String src)
6. decrypt(String seed, String encrypted)
7. decrypt(String seed, String encrypted)