Use RSA from bouncy castle - Java Security

Java examples for Security:RSA

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Description

Use RSA from bouncy castle

Demo Code

import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.SecureRandom;
import java.security.Security;
import java.util.Date;
import java.sql.Timestamp;
import java.math.*;

import org.bouncycastle.crypto.AsymmetricBlockCipher;
import org.bouncycastle.crypto.AsymmetricCipherKeyPair;
import org.bouncycastle.crypto.InvalidCipherTextException;
import org.bouncycastle.crypto.engines.RSAEngine;
import org.bouncycastle.crypto.generators.RSAKeyPairGenerator;
import org.bouncycastle.crypto.params.AsymmetricKeyParameter;
import org.bouncycastle.crypto.params.RSAKeyGenerationParameters;
import org.bouncycastle.jce.provider.BouncyCastleProvider;

public class rsa {

    public static String getHexString(byte[] b) throws Exception {
        String result = "";
        for (int i = 0; i < b.length; i++) {
            result += Integer.toString((b[i] & 0xff) + 0x100, 16)
                    .substring(1);/*from   www  .j  av a 2  s . c o m*/
        }
        return result;
    }

    public static byte[] hexStringToByteArray(String s) {
        int len = s.length();
        byte[] data = new byte[len / 2];
        for (int i = 0; i < len; i += 2) {
            data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character
                    .digit(s.charAt(i + 1), 16));
        }
        return data;
    }

    public static void GetTimestamp(String info) {
        System.out.println(info + new Timestamp((new Date()).getTime()));
    }

    public static AsymmetricCipherKeyPair GenerateKeys()
            throws NoSuchAlgorithmException {
        //  Source: http://stackoverflow.com/questions/3087049/bouncy-castle-rsa-keypair-generation-using-lightweight-api
        RSAKeyPairGenerator generator = new RSAKeyPairGenerator();
        generator.init(new RSAKeyGenerationParameters(new BigInteger(
                "10001", 16),//publicExponent
                SecureRandom.getInstance("SHA1PRNG"),//pseudorandom number generator
                4096,//strength
                80//certainty
                ));

        return generator.generateKeyPair();
    }

    public static String Encrypt(byte[] data,
            AsymmetricKeyParameter publicKey) throws Exception {
        //  Source: http://www.cs.berkeley.edu/~jonah/bc/org/bouncycastle/crypto/engines/RSAEngine.html  
        Security.addProvider(new BouncyCastleProvider());

        RSAEngine engine = new RSAEngine();
        engine.init(true, publicKey); //true if encrypt

        byte[] hexEncodedCipher = engine.processBlock(data, 0, data.length);

        return getHexString(hexEncodedCipher);
    }

    public static String Decrypt(String encrypted,
            AsymmetricKeyParameter privateKey)
            throws InvalidCipherTextException {

        Security.addProvider(new BouncyCastleProvider());

        AsymmetricBlockCipher engine = new RSAEngine();
        engine.init(false, privateKey); //false for decryption

        byte[] encryptedBytes = hexStringToByteArray(encrypted);
        byte[] hexEncodedCipher = engine.processBlock(encryptedBytes, 0,
                encryptedBytes.length);

        return new String(hexEncodedCipher);
    }

    public static void main(String[] args) throws Exception {

        GetTimestamp("Key Pair Generation started: ");
        AsymmetricCipherKeyPair keyPair = GenerateKeys();
        GetTimestamp("Key Pair Generation ended: ");

        String plainMessage = "plaintext";

        GetTimestamp("Encryption started: ");
        String encryptedMessage = Encrypt(plainMessage.getBytes("UTF-8"),
                keyPair.getPublic());
        System.out.println(encryptedMessage);
        GetTimestamp("Encryption ended: ");

        GetTimestamp("Decryption started: ");
        String decryptedMessage = Decrypt(encryptedMessage,
                keyPair.getPrivate());
        System.out.println("Plain text was: " + plainMessage
                + " and decrypted text is: " + decryptedMessage);
        GetTimestamp("Decryption ended: ");

    }

}

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