package encryption;

import java.security.Key;
import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;


public class DesEncrypt {
    Key key;

    //獲取密鑰的方法；============================================================
    public void getKey(String strKey) {
        try {
            KeyGenerator keyGenerator = KeyGenerator.getInstance("DES");
            keyGenerator.init(new SecureRandom(strKey.getBytes()));
            this.key = keyGenerator.generateKey();
            keyGenerator = null;
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    //將明文加密的方法；==========================================================
    public String getEncString(String strMing) {
        byte[] byteMi = null;
        byte[] byteMing = null;
        String strMi = "";
        BASE64Encoder base64en = new BASE64Encoder();
        try {
            byteMing = strMing.getBytes("UTF8");
            byteMi = this.getEncCode(byteMing);
            strMi = base64en.encode(byteMi);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            base64en = null;
            byteMing = null;
            byteMi = null;
        }
        return strMi;
    }

    //將密文解密的方法============================================================
    public String getDecString(String strMi) {
        BASE64Decoder base64De = new BASE64Decoder();
        byte[] byteMing = null;
        byte[] byteMi = null;
        String strMing = "";
        try {
            byteMi = base64De.decodeBuffer(strMi);
            byteMing = this.getDecCode(byteMi);
            strMing = new String(byteMing, "UTF8");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            base64De = null;
            byteMing = null;
            byteMi = null;
        }
        return strMing;
    }

    //明文字節串迭代成密文字節串的方法==============================================
    private byte[] getEncCode(byte[] byteS) {
        byte[] byteFina = null;
        Cipher cipher;
        try {
            cipher = Cipher.getInstance("DES");
            cipher.init(Cipher.ENCRYPT_MODE, key);
            byteFina = cipher.doFinal(byteS);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            cipher = null;
        }
        return byteFina;
    }

    //密文字節串換算成明文字節串的方法==============================================
    private byte[] getDecCode(byte[] byteD) {
        Cipher cipher;
        byte[] byteFina = null;
        try {
            cipher = Cipher.getInstance("DES");
            cipher.init(Cipher.DECRYPT_MODE, key);
            byteFina = cipher.doFinal(byteD);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            cipher = null;
        }
        return byteFina;
    }

}