Dazed and confused by Java Security & BouncyCastle APIs

Question

I\'ve been trying to make sense of the BouncyCastle cryptography APIs for Java. Unfortunately, I\'m finding Java cryptography in general to be so obscured by service provider in

Answer 1

import java.security.GeneralSecurityException;
import java.security.KeyFactory;
import java.security.KeyPairGenerator;
import java.security.PublicKey;
import java.security.interfaces.RSAPrivateKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

import javax.crypto.Cipher;

public class RsaCrypto {

    private static final int KEY_SIZE = 3072;
    private static final String TRANSFORMATION = "RSA/ECB/OAEPWITHSHA-256ANDMGF1PADDING";

    public static KeyPair generateRSAKeyPair() {
        try {
            KeyPairGenerator gen = KeyPairGenerator.getInstance("RSA");
            gen.initialize(KEY_SIZE);
            java.security.KeyPair p = gen.generateKeyPair();
            KeyPair pair = new KeyPair();
            pair.privateKey = p.getPrivate().getEncoded();
            pair.publicKey = p.getPublic().getEncoded();
            return pair;
        } catch (GeneralSecurityException e) {
            throw new RuntimeException(e);
        }

    }

    public static byte[] encrypt(byte[] data, byte[] publicKey) {
        X509EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(publicKey);
        try {
            KeyFactory kf = KeyFactory.getInstance("RSA");
            PublicKey pk = kf.generatePublic(publicKeySpec);
            Cipher rsa = Cipher.getInstance(TRANSFORMATION);
            rsa.init(Cipher.ENCRYPT_MODE, pk);
            return rsa.doFinal(data);
        } catch (GeneralSecurityException e) {
            throw new RuntimeException(e);
        }
    }

    public static byte[] decrypt(byte[] encryptedData, byte[] privateKey) {
        try {
            PKCS8EncodedKeySpec privSpec = new PKCS8EncodedKeySpec(privateKey);
            RSAPrivateKey pk = (RSAPrivateKey) KeyFactory.getInstance("RSA")
                    .generatePrivate(privSpec);

            Cipher rsaCipher = Cipher.getInstance(TRANSFORMATION);
            rsaCipher.init(Cipher.DECRYPT_MODE, pk);
            return rsaCipher.doFinal(encryptedData);

        } catch (GeneralSecurityException e) {
            throw new RuntimeException(e);
        }
    }

}