AES CryptoUtils

Posted 2022-01-07 lhp2012

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.SecureRandom;
import java.util.Base64;

import static java.nio.charset.StandardCharsets.UTF_8;

public class CryptoUtils 

    private static AesCrypto textCrypto = null; // key for text data

    public static void init(String key) 
        if (textCrypto == null) 
            textCrypto = new AesCrypto(key);
        
    


    public static String decryptText(final String cypherData) 
        return new String(textCrypto.decryptBytes(TrimBase64.decode(cypherData)), UTF_8);
    

    public static String encryptText(final String planData) 
        return TrimBase64.encode(textCrypto.encryptBytes(planData.getBytes(UTF_8)));
    

    private static class TrimBase64 
        private static byte[] decode(String text) 
            if (text == null) 
                return null;
            
            // padding trailing ‘=‘
            int length = text.length();
            switch (length % 4) 
                case 2:
                    text += "==";
                    break;
                case 1:
                    text += "===";
                    break;
                case 3:
                    text += "=";
                    break;
                default:
                    break;
            
            return Base64.getDecoder().decode(text);
        

        private static String encode(byte[] data) 
            // trim trailing ‘=‘
            return data == null ? null : Base64.getEncoder().encodeToString(data).replaceAll("=*$", "");
        
    

    private static class AesCrypto 

        private final SecretKeySpec keySpec;
        private final SecureRandom srandom;

        AesCrypto(String hexKey) 
            if (!testKeys(hexKey)) 
                throw new RuntimeException("AES Key invalid");
            
            keySpec = new SecretKeySpec(fromHex(hexKey), "AES");
            srandom = new SecureRandom();
        

        /**
         * AES-128/192/256 allowed
         *
         * @param hexKey
         * @return
         */
        private boolean testKeys(String hexKey) 
            return hexKey != null && (hexKey.length() == 32 || hexKey.length() == 48 || hexKey.length() == 64);
        

        private byte[] fromHex(String hexStr) 
            if (hexStr == null) 
                return null;
            
            int length = hexStr.length();
            if (length % 2 == 1) 
                return null;
            
            int byteLength = length / 2;
            byte[] raw = new byte[byteLength];
            for (int i = 0; i < byteLength; i++) 
                raw[i] = (byte) Integer.parseInt(hexStr.substring(i + i, i + i + 2), 16);
            
            return raw;
        

        private byte[] decryptBytes(byte[] sBytes) 
            if (sBytes == null) 
                return null;
            
            try 
                Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
                int ivSize = cipher.getBlockSize();
                IvParameterSpec ivSpec = new IvParameterSpec(sBytes, 0, ivSize);
                cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);
                byte[] payload = cipher.doFinal(sBytes, ivSize, sBytes.length - ivSize);
                return payload;
             catch (Exception e) 
                e.printStackTrace();
                return null;
            
        

        private byte[] encryptBytes(byte[] sBytes) 
            if (sBytes == null) 
                return null;
            
            try 
                Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
                byte[] iv = new byte[cipher.getBlockSize()];
                srandom.nextBytes(iv);
                IvParameterSpec ivSpec = new IvParameterSpec(iv);
                cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
                byte[] payload = cipher.doFinal(sBytes);
                byte[] encrypted = new byte[iv.length + payload.length];
                System.arraycopy(iv, 0, encrypted, 0, iv.length);
                System.arraycopy(payload, 0, encrypted, iv.length, payload.length);
                return encrypted;
             catch (Exception e) 
                e.printStackTrace();
                return null;