51 lines
1.8 KiB
Java
51 lines
1.8 KiB
Java
/**
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* Copyright (C) 2014 Open Whisper Systems
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package org.whispersystems.libaxolotl.ratchet;
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import org.whispersystems.libaxolotl.InvalidKeyException;
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import org.whispersystems.libaxolotl.ecc.Curve;
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import org.whispersystems.libaxolotl.ecc.ECKeyPair;
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import org.whispersystems.libaxolotl.ecc.ECPublicKey;
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import org.whispersystems.libaxolotl.kdf.DerivedSecrets;
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import org.whispersystems.libaxolotl.kdf.HKDF;
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import org.whispersystems.libaxolotl.util.Pair;
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public class RootKey {
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private final byte[] key;
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public RootKey(byte[] key) {
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this.key = key;
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}
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public byte[] getKeyBytes() {
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return key;
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}
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public Pair<RootKey, ChainKey> createChain(ECPublicKey theirEphemeral, ECKeyPair ourEphemeral)
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throws InvalidKeyException
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{
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HKDF kdf = new HKDF();
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byte[] sharedSecret = Curve.calculateAgreement(theirEphemeral, ourEphemeral.getPrivateKey());
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DerivedSecrets keys = kdf.deriveSecrets(sharedSecret, key, "WhisperRatchet".getBytes());
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RootKey newRootKey = new RootKey(keys.getCipherKey().getEncoded());
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ChainKey newChainKey = new ChainKey(keys.getMacKey().getEncoded(), 0);
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return new Pair<>(newRootKey, newChainKey);
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}
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}
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