org.fdroid.enigtext.crypto.MasterSecret.java Source code

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Here is the source code for org.fdroid.enigtext.crypto.MasterSecret.java

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/**
 * Copyright (C) 2011 Whisper Systems
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.fdroid.enigtext.crypto;

import android.os.Parcel;
import android.os.Parcelable;

import org.bouncycastle.util.Arrays;

import javax.crypto.spec.SecretKeySpec;

/**
 * When a user first initializes TextSecure, a few secrets
 * are generated.  These are:
 *
 * 1) A 128bit symmetric encryption key.
 * 2) A 160bit symmetric MAC key.
 * 3) An ECC keypair.
 *
 * The first two, along with the ECC keypair's private key, are
 * then encrypted on disk using PBE.
 *
 * This class represents 1 and 2.
 *
 * @author Moxie Marlinspike
 */

public class MasterSecret implements Parcelable {

    private final SecretKeySpec encryptionKey;
    private final SecretKeySpec macKey;

    public static final Parcelable.Creator<MasterSecret> CREATOR = new Parcelable.Creator<MasterSecret>() {
        @Override
        public MasterSecret createFromParcel(Parcel in) {
            return new MasterSecret(in);
        }

        @Override
        public MasterSecret[] newArray(int size) {
            return new MasterSecret[size];
        }
    };

    public MasterSecret(SecretKeySpec encryptionKey, SecretKeySpec macKey) {
        this.encryptionKey = encryptionKey;
        this.macKey = macKey;
    }

    private MasterSecret(Parcel in) {
        byte[] encryptionKeyBytes = new byte[in.readInt()];
        in.readByteArray(encryptionKeyBytes);

        byte[] macKeyBytes = new byte[in.readInt()];
        in.readByteArray(macKeyBytes);

        this.encryptionKey = new SecretKeySpec(encryptionKeyBytes, "AES");
        this.macKey = new SecretKeySpec(macKeyBytes, "HmacSHA1");

        // SecretKeySpec does an internal copy in its constructor.
        Arrays.fill(encryptionKeyBytes, (byte) 0x00);
        Arrays.fill(macKeyBytes, (byte) 0x00);
    }

    public SecretKeySpec getEncryptionKey() {
        return this.encryptionKey;
    }

    public SecretKeySpec getMacKey() {
        return this.macKey;
    }

    @Override
    public void writeToParcel(Parcel out, int flags) {
        out.writeInt(encryptionKey.getEncoded().length);
        out.writeByteArray(encryptionKey.getEncoded());
        out.writeInt(macKey.getEncoded().length);
        out.writeByteArray(macKey.getEncoded());
    }

    @Override
    public int describeContents() {
        return 0;
    }

    public MasterSecret parcelClone() {
        Parcel thisParcel = Parcel.obtain();
        Parcel thatParcel = Parcel.obtain();
        byte[] bytes = null;

        thisParcel.writeValue(this);
        bytes = thisParcel.marshall();

        thatParcel.unmarshall(bytes, 0, bytes.length);
        thatParcel.setDataPosition(0);

        MasterSecret that = (MasterSecret) thatParcel.readValue(MasterSecret.class.getClassLoader());

        thisParcel.recycle();
        thatParcel.recycle();

        return that;
    }

}