source: trunk/src/org/expeditee/auth/sharing/Actions.java@ 1260

package org.expeditee.auth.sharing;

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.Base64;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

import org.expeditee.gui.DisplayController;
import org.expeditee.gui.Frame;
import org.expeditee.gui.FrameIO;
import org.expeditee.items.Text;
import org.ngikm.cryptography.CryptographyConstants;

import com.codahale.shamir.Scheme;

public class Actions implements CryptographyConstants {
        
        public static Text GenerateSecret(String label) {
                return AuthGenerateSecret(label);
        }
        
        public static Text SplitSecret(Text key) {
                return AuthSplitSecret(key);
        }
        
        public static Text JoinSecret(Text key) {
                return AuthJoinSecret(key);
        }

        public static Text AuthGenerateSecret(String label) {
                // Generate AES Key
                Random rand = new SecureRandom();
                byte[] keyBytes = new byte[16];
                rand.nextBytes(keyBytes);
                String key = Base64.getEncoder().encodeToString(keyBytes);
                
                Text text = new Text(label);
                text.setData(key);
                text.setPosition(DisplayController.getMousePosition());
                return text;
        }

        public static Text AuthSplitSecret(Text key) {
                // Retrieve secret
                String secret = key.getData().get(0);
                byte[] secretBytes = Base64.getDecoder().decode(secret);
                
                // Obtain parameters for shamir
                String[] arguments = key.getText().split(" ");
                int totalShares = Integer.parseInt(arguments[1]);
                int requiredShares = Integer.parseInt(arguments[2]);
                
                // Create shares
                Scheme scheme = new Scheme(new SecureRandom(), totalShares, requiredShares);
                Map<Integer, byte[]> split = scheme.split(secretBytes);
                
                // Add shares to key
                List<String> data = key.getData();
                for (Integer i: split.keySet()) {
                        data.add("{" + i + "}" + Base64.getEncoder().encodeToString(split.get(i)));
                }
                key.setData(data);
                
                return key;
        }
        
        public static Text AuthJoinSecret(Text key) {
                Map<Integer, byte[]> contributingParts = new HashMap<Integer, byte[]>();
                
                // Retrieve splits
                List<String> data = key.getData();
                for (String d: data) {
                        if (d.startsWith("{")) {
                                String[] split = d.split("}");
                                Integer k = Integer.parseInt(split[0].replace("{", ""));
                                byte[] v = Base64.getDecoder().decode(split[1]);
                                contributingParts.put(k, v);
                        }
                }
                
                // Obtain parameters for shamir
                String[] arguments = key.getText().split(" ");
                int totalShares = Integer.parseInt(arguments[1]);
                int requiredShares = Integer.parseInt(arguments[2]);
                
                // Perform join
                Scheme scheme = new Scheme(new SecureRandom(), totalShares, requiredShares);
                byte[] join = scheme.join(contributingParts);
                
                data.clear();
                data.add(Base64.getEncoder().encodeToString(join));
                
                return key;
        }
        
        public static void AuthEncrypt(Text labelWithKey) {
                // Obtain encryption key
                String keyEncoded = labelWithKey.getData().get(0);
                byte[] keyDecoded = Base64.getDecoder().decode(keyEncoded);
                SecretKey key = new SecretKeySpec(keyDecoded, SymmetricAlgorithm);
                
                // Perform encryption
                Frame toEncrypt = FrameIO.LoadFrame(labelWithKey.getLink());
                Collection<Text> textItems = toEncrypt.getTextItems();
                for (Text t: textItems) {
                        byte[] encrypted = EncryptSymmetric(t.getText().getBytes(), key);
                        t.setText(Base64.getEncoder().encodeToString(encrypted));
                }
                
                // Save changes
                FrameIO.SaveFrame(toEncrypt);
        }
        
        public static void AuthDecrypt(Text labelWithKey) {
                // Obtain encryption key
                String keyEncoded = labelWithKey.getData().get(0);
                byte[] keyDecoded = Base64.getDecoder().decode(keyEncoded);
                SecretKey key = new SecretKeySpec(keyDecoded, SymmetricAlgorithm);
                
                // Perform decryption
                Frame toEncrypt = FrameIO.LoadFrame(labelWithKey.getLink());
                Collection<Text> textItems = toEncrypt.getTextItems();
                for (Text t: textItems) {
                        byte[] decrypted = DecryptSymmetric(Base64.getDecoder().decode(t.getText().getBytes()), key);
                        t.setText(new String(decrypted));
                }
        }
        
        private static byte[] EncryptSymmetric(final byte[] toEncrypt, final SecretKey key) {
                // toEncrypt = Base64.getDecoder().decode(toEncrypt);
                try {
                        final Cipher cipher = Cipher.getInstance(SymmetricAlgorithm + SymmetricAlgorithmParameters);
                        cipher.init(Cipher.ENCRYPT_MODE, key);
                        //could use modulus
                        final int length = (int) ((Math.ceil(toEncrypt.length / 16f)) * 16);
                        final byte[] toEncryptSizeAdjusted = Arrays.copyOf(toEncrypt, length);
                        //System.err.println("(" + toEncryptSizeAdjusted.length + ")" + "Before Encryption Data: "
                        //              + Arrays.toString(toEncryptSizeAdjusted));
                        final byte[] result = cipher.doFinal(toEncryptSizeAdjusted);
                        //System.err.println("(" + result.length + ")" + "Encrypted Data: " + Arrays.toString(result));
                        return result;
                } catch (final NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException
                                | IllegalBlockSizeException | BadPaddingException e) {
                        e.printStackTrace();
                        return null;
                }
        }

        private static byte[] DecryptSymmetric(final byte[] toDecrypt, final SecretKey key) {
                try {
                        final Cipher cipher = Cipher.getInstance(SymmetricAlgorithm + SymmetricAlgorithmParameters);
                        cipher.init(Cipher.DECRYPT_MODE, key);
                        final byte[] decryptedBytes = cipher.doFinal(toDecrypt);
                        int indexOfZero = decryptedBytes.length - 1;
                        for (int i = decryptedBytes.length - 1; i >= 0; i--) {
                                if (decryptedBytes[i] != (byte) 0) {
                                        indexOfZero = i + 1;
                                        break;
                                }
                        }
                        return Arrays.copyOf(decryptedBytes, indexOfZero);
                } catch (final NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException
                                | IllegalBlockSizeException | BadPaddingException e) {
                        e.printStackTrace();
                        return null;
                }
        }
}