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User guide

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Online Java Compiler

This tool allows to compile and execute Java online directly in your browser.

This Java playground can be useful to make small tests without installation.

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import java.security.KeyPair;
import java.security.KeyFactory;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import javax.crypto.Cipher;

public class CryptoExample {

    public static byte[] encrypt(byte[] publicKey, byte[] dataToEncrypt) throws Exception {
        PublicKey key = KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(publicKey));
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, key);
        return cipher.doFinal(dataToEncrypt);
    }

    public static byte[] decrypt(byte[] privateKey, byte[] dataToDecrypt) throws Exception {
        PrivateKey key = KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(privateKey));
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, key);
        return cipher.doFinal(dataToDecrypt);
    }

    public static KeyPair generateKeys() throws Exception {
        KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
        SecureRandom random = SecureRandom.getInstance("SHA1PRNG", "SUN");
        keyGen.initialize(512, random);
        return keyGen.generateKeyPair();
    }

    public static void main(String[] args) throws Exception {
        // Generate keys 
		KeyPair keys = generateKeys();
        byte[] publicKey = keys.getPublic().getEncoded();
        byte[] privateKey = keys.getPrivate().getEncoded();

        // Encrypt string with public key
		byte[] encryptedData = encrypt(publicKey, "String to crypt".getBytes());

        // Decrypt string with private key
        byte[] decryptedData = decrypt(privateKey, encryptedData);

		// Print decrypted string
        System.out.println(new String(decryptedData));
    }
}