Android Open Source

 RSA Java Crypto Project

MainActivity.java

Full working example. The markup is given in the previous post.

package org.o7planning.rsa;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.Base64;
import android.util.Log;
import android.view.View;
import android.widget.TextView;

import java.security.Key;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.Provider;
import java.security.Security;
import java.util.Iterator;
import java.util.TreeSet;

import javax.crypto.Cipher;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);



        // Original text
        String testText = "Open Source Java Project";
        TextView originalTextView = (TextView) findViewById(R.id.TXTV);
        originalTextView.setText("[ORIGINAL]:\n" + testText + "\n");

        // Generate key pair for 1024-bit RSA encryption and decryption
        Key publicKey = null;
        Key privateKey = null;
        try {
            KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
            kpg.initialize(1024);
            KeyPair kp = kpg.genKeyPair();
            publicKey = kp.getPublic();
            privateKey = kp.getPrivate();
        } catch (Exception e) {
            Log.e("Crypto", "RSA key pair error");
        }

        // Encode the original data with RSA private key
        byte[] encodedBytes = null;
        try {
            Cipher c = Cipher.getInstance("RSA");
            c.init(Cipher.ENCRYPT_MODE, privateKey);
            encodedBytes = c.doFinal(testText.getBytes());
        } catch (Exception e) {
            Log.e("Crypto", "RSA encryption error");
        }
        TextView encodedTextView = (TextView)findViewById(R.id.textViewEncoded);
        encodedTextView.setText("[ENCODED]:\n" + Base64.encodeToString(encodedBytes, Base64.DEFAULT) + "\n");

        // Decode the encoded data with RSA public key
        byte[] decodedBytes = null;
        try {
            Cipher c = Cipher.getInstance("RSA");
            c.init(Cipher.DECRYPT_MODE, publicKey);
            decodedBytes = c.doFinal(encodedBytes);
        } catch (Exception e) {
            Log.e("Crypto", "RSA decryption error");
        }

        TextView decodedTextView = (TextView)findViewById(R.id.textViewDecoded);
        decodedTextView.setText("[DECODED]:\n" + new String(decodedBytes) + "\n");
    }












}


(c( by Valery Shmelev  https://www.linkedin.com/in/valery-shmelev-479206227/ 

RSA Java Crypto Project


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