package testesignature;

import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.Signature;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

import org.apache.commons.io.IOUtils;
import org.junit.Assert;
import org.junit.Test;

public class TheTest {

    @Test
    public void shouldCreateKeys() throws Exception {
        KeyPairGenerator keyGen = KeyPairGenerator.getInstance("DSA");
        SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
        keyGen.initialize(1024, random);
        KeyPair pairSig = keyGen.generateKeyPair();
        PrivateKey privSig = pairSig.getPrivate();
        PublicKey pubSig = pairSig.getPublic();
        Files.write(Paths.get("priv.key"), privSig.getEncoded());
        Files.write(Paths.get("pub.key"), pubSig.getEncoded());

        KeyGenerator kgen = KeyGenerator.getInstance("AES");
        kgen.init(128);
        SecretKey key = kgen.generateKey();
        Files.write(Paths.get("secret.key"), key.getEncoded());
    }

    @Test
    public void shouldSignImage() throws Exception {

        Path pPrivKey = Paths.get("priv.key");
        byte[] bPriv = Files.readAllBytes(pPrivKey);
        PKCS8EncodedKeySpec xPriv = new PKCS8EncodedKeySpec(bPriv);

        KeyFactory keyFactory = KeyFactory.getInstance("DSA");
        PrivateKey priv = keyFactory.generatePrivate(xPriv);

        Path pImg = Paths.get("19244.jpg");
        byte[] bImg = Files.readAllBytes(pImg);

        Signature dsa = Signature.getInstance("SHA1withDSA");
        dsa.initSign(priv);
        dsa.update(bImg);
        Path pSigImg = Paths.get("19244.jpg.sig");
        Files.write(pSigImg, dsa.sign());

    }

    @Test
    public void shouldVerifyImageSignature() throws Exception {

        Path pPubKey = Paths.get("pub.key");
        byte[] bPub = Files.readAllBytes(pPubKey);
        X509EncodedKeySpec xPub = new X509EncodedKeySpec(bPub);

        KeyFactory keyFactory = KeyFactory.getInstance("DSA");
        PublicKey pub = keyFactory.generatePublic(xPub);

        Path pImg = Paths.get("19244.jpg");
        byte[] bImg = Files.readAllBytes(pImg);

        Path pSigImg = Paths.get("19244.jpg.sig");

        Signature dsb = Signature.getInstance("SHA1withDSA");
        dsb.initVerify(pub);
        dsb.update(bImg);
        Assert.assertTrue(dsb.verify(Files.readAllBytes(pSigImg)));
    }

    @Test
    public void shouldEncryptImage() throws Exception {

        Path pImg = Paths.get("19244.jpg");
        byte[] bImg = Files.readAllBytes(pImg);

        Path pCrypImg = Paths.get("19244.jpg.cryp");
        SecretKey key = new SecretKeySpec(Files.readAllBytes(Paths
                .get("secret.key")), "AES");

        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, key);
        try (OutputStream out = new CipherOutputStream(
                Files.newOutputStream(pCrypImg), cipher)) {
            out.write(bImg);
            out.flush();
        }
    }

    @Test
    public void shouldDecryptImage() throws Exception {

        Path pCrypImg = Paths.get("19244.jpg.cryp");

        SecretKey key = new SecretKeySpec(Files.readAllBytes(Paths
                .get("secret.key")), "AES");

        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.DECRYPT_MODE, key);

        try (InputStream in = new CipherInputStream(
                Files.newInputStream(pCrypImg), cipher)) {
            try (OutputStream out = new FileOutputStream("19244-decryp.jpg")) {
                IOUtils.copy(in, out);
            }
        }
    }
}