CryptographicChecksum.java

package com.vasudev.msgdigest;

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

import android.app.Activity;
import android.app.AlertDialog;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RadioGroup;
import android.widget.RadioGroup.OnCheckedChangeListener;
import android.widget.TextView;

public class MSGDigestGenerator extends Activity implements OnClickListener,
		OnCheckedChangeListener {
	private EditText stringHash = null;
	private Button btnGenerate = null;
	private TextView txtHash = null;
	private RadioGroup algorithGroup = null;
	private String hashAlgorithm = null;

	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

		stringHash = (EditText) findViewById(R.id.string);
		btnGenerate = (Button) findViewById(R.id.generate);
		txtHash = (TextView) findViewById(R.id.hash);
		algorithGroup = (RadioGroup) findViewById(R.id.algorithm);

		btnGenerate.setOnClickListener(this);
		algorithGroup.setOnCheckedChangeListener(this);
	}

	@Override
	public void onClick(View v) {
		// TODO Auto-generated method stub
		if (hashAlgorithm == null) {
			AlertDialog.Builder builder = new AlertDialog.Builder(this);
			builder.setTitle("Form In Complete!");
			builder.setMessage("Please Select an Algorithm to generate Hash.");
			builder.setPositiveButton("OK", null);
			builder.create().show();
			
			return;
		}
		try {
			txtHash.setText((generateHash(stringHash.getText().toString(),hashAlgorithm)));
		} catch (NoSuchAlgorithmException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

	}

	private String generateHash(String string,String alg) throws NoSuchAlgorithmException {
		// TODO Auto-generated method stub
		MessageDigest algorithm = MessageDigest.getInstance(alg);
		algorithm.update(string.getBytes());

		byte[] digest = algorithm.digest();

		StringBuffer buffer = new StringBuffer();
		for (int i = 0; i < digest.length; i++) {
			String h = Integer.toHexString(0xFF & digest[i]);
			while (h.length() < 2)
				h = "0" + h;
			buffer.append(h);
		}

		return buffer.toString();
	}

	@Override
	public void onCheckedChanged(RadioGroup group, int checkedId) {
		// TODO Auto-generated method stub
		switch (checkedId) {
		case R.id.md5:
			hashAlgorithm = "MD5";
			break;
		case R.id.sha1:
			hashAlgorithm = "SHA-1";
			break;
		case R.id.sha256:
			hashAlgorithm = "SHA-256";
			break;
		case R.id.sha512:
			hashAlgorithm = "SHA-512";
			break;
		default:
			break;
		}
	}
}

Sample for Generating cryptographic checksum in android