EncodeIdentity.java

package com.fellstat.secureidentityencoder;

import android.content.DialogInterface;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class EncodeIdentity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_encode_identity);
        final Button clickButton = (Button) findViewById(R.id.button);
        final EditText key = (EditText) findViewById(R.id.key);
        final EditText fn = (EditText) findViewById(R.id.firstname);
        final EditText ln = (EditText) findViewById(R.id.lastname);
        final TextView codeText = (TextView) findViewById(R.id.codetext);
        final String salt = "1234567";
        clickButton.setOnClickListener( new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String first = fn.getText().toString().toLowerCase().trim();
                String last = ln.getText().toString().toLowerCase().trim();
                int lastLength = Math.min(3,last.length());
                last = last.substring(0,lastLength);

                if(first.length() == 0 || last.length() == 0){
                    AlertDialog alertDialog = new AlertDialog.Builder(EncodeIdentity.this).create();
                    alertDialog.setTitle("Alert");
                    alertDialog.setMessage("first and last name may not be empty");
                    alertDialog.setButton(AlertDialog.BUTTON_NEUTRAL, "OK",
                            new DialogInterface.OnClickListener() {
                                public void onClick(DialogInterface dialog, int which) {
                                    dialog.dismiss();
                                }
                            });
                    alertDialog.show();
                    key.setText("", TextView.BufferType.EDITABLE);
                    codeText.setText("", TextView.BufferType.EDITABLE);
                    return;
                }

                String code = first + ":" + last;
                String hash = hash(code,salt);
                hash = hash.substring(0, Math.min(9,hash.length()));
                key.setText(hash, TextView.BufferType.EDITABLE);
                codeText.setText(code, TextView.BufferType.EDITABLE);

            }
        });
    }

    //http://howtodoinjava.com/security/how-to-generate-secure-password-hash-md5-sha-pbkdf2-bcrypt-examples/
    public static String hash(String passwordToHash, String salt)
    {
        String generatedPassword = null;
        try {
            MessageDigest md = MessageDigest.getInstance("SHA-512");
            md.update(salt.getBytes());
            byte[] bytes = md.digest(passwordToHash.getBytes());
            StringBuilder sb = new StringBuilder();
            for(int i=0; i< bytes.length ;i++)
            {
                sb.append(Integer.toString((bytes[i] & 0xff) + 0x100, 16).substring(1));
            }
            generatedPassword = sb.toString();
        }
        catch (NoSuchAlgorithmException e)
        {
            e.printStackTrace();
            return null;
        }
        return generatedPassword;
    }
}