Decrypt Base64 encoded encrypted string - Android java.security

Android examples for java.security:Password

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Description

Decrypt Base64 encoded encrypted string

Demo Code


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

public class Main {
    /**//from   ww  w .  j  a v a  2  s . com
     * Decrypt Base64 encoded encrypted string
     *
     * @param seed
     * @param encrypted
     * @return
     * @throws Exception
     */
    public static String decrypt(String seed, String encrypted)
            throws Exception {
        byte[] rawKey = getRawKey(seed.getBytes());
        byte[] enc = Base64.decode(encrypted.getBytes(), Base64.DEFAULT);
        byte[] result = decrypt(rawKey, enc);
        return new String(result);
    }

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

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

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