KeyPairReader.java

package java2.koz01.lab13;

import java.io.BufferedReader;
import java.io.IOException;
import java.math.BigInteger;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.NoSuchAlgorithmException;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.RSAPrivateKeySpec;
import java.security.spec.RSAPublicKeySpec;

public class KeyPairReader {

	private KeyFactory factory;

	public KeyPairReader() throws NoSuchAlgorithmException {
		factory = KeyFactory.getInstance("rsa");
	}

	public KeyPair readKeys(String fileWithKeys) throws IOException,
		InvalidKeySpecException
	{
//open file
//Read first line-> modulus
//...
//create RSAPublicKeySpec 		
		try (BufferedReader br = Files.newBufferedReader(Paths.get(fileWithKeys))) {
			BigInteger modulus = new BigInteger(br.readLine());
			BigInteger publicExponent = new BigInteger(br.readLine());
			BigInteger privateExponent = new BigInteger(br.readLine());
			RSAPublicKeySpec pub = new RSAPublicKeySpec(modulus, publicExponent);
			RSAPrivateKeySpec pri = new RSAPrivateKeySpec(modulus, privateExponent);
			return new KeyPair(factory.generatePublic(pub), factory.generatePrivate(
				pri));
		}
	}
}