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/**
* Copyright (C) 2014 Open 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.whispersystems.libaxolotl.ratchet;
import org.whispersystems.libaxolotl.InvalidKeyException;
import org.whispersystems.libaxolotl.ecc.Curve;
import org.whispersystems.libaxolotl.ecc.ECKeyPair;
import org.whispersystems.libaxolotl.ecc.ECPublicKey;
import org.whispersystems.libaxolotl.kdf.DerivedRootSecrets;
import org.whispersystems.libaxolotl.kdf.HKDF;
import org.whispersystems.libaxolotl.util.ByteUtil;
import org.whispersystems.libaxolotl.util.Pair;
public class RootKey {
private final HKDF kdf;
private final byte[] key;
public RootKey(HKDF kdf, byte[] key) {
this.kdf = kdf;
this.key = key;
}
public byte[] getKeyBytes() {
return key;
}
public Pair<RootKey, ChainKey> createChain(ECPublicKey theirRatchetKey, ECKeyPair ourRatchetKey)
throws InvalidKeyException
{
byte[] sharedSecret = Curve.calculateAgreement(theirRatchetKey, ourRatchetKey.getPrivateKey());
byte[] derivedSecretBytes = kdf.deriveSecrets(sharedSecret, key, "WhisperRatchet".getBytes(), DerivedRootSecrets.SIZE);
DerivedRootSecrets derivedSecrets = new DerivedRootSecrets(derivedSecretBytes);
RootKey newRootKey = new RootKey(kdf, derivedSecrets.getRootKey());
ChainKey newChainKey = new ChainKey(kdf, derivedSecrets.getChainKey(), 0);
return new Pair<>(newRootKey, newChainKey);
}
}
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