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109 lines
3.2 KiB
109 lines
3.2 KiB
/*
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This file is part of cpp-ethereum.
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cpp-ethereum 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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cpp-ethereum 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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You should have received a copy of the GNU General Public License
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along with cpp-ethereum. If not, see <http://www.gnu.org/licenses/>.
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*/
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/** @file ECDHE.h
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* @author Alex Leverington <nessence@gmail.com>
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* @date 2014
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*
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* Elliptic curve Diffie-Hellman ephemeral key exchange
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*/
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#pragma once
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#include "AES.h"
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namespace dev
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{
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namespace crypto
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{
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/// Public key of remote and corresponding shared secret.
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typedef std::pair<Public,h256> AliasSession;
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/**
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* @brief An addressable EC key pair.
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*/
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class Alias
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{
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friend class ECDHEKeyExchange; // todo: remove
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public:
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Alias(Secret _s): m_secret(_s) {};
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AliasSession session(Address _a) { return m_sessions.count(_a) ? m_sessions.find(_a)->second : AliasSession(); }
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private:
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std::map<Address,AliasSession> m_sessions;
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Secret m_secret;
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};
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/**
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* @brief Derive DH shared secret from EC keypairs.
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* As ephemeral keys are single-use, agreement is limited to a single occurence.
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*/
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class ECDHE
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{
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public:
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/// Constructor (pass public key for ingress exchange).
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ECDHE(): m_ephemeral(KeyPair::create()) {};
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/// Public key sent to remote.
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Public pubkey() { return m_ephemeral.pub(); }
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/// Input public key for dh agreement, output generated shared secret.
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void agree(Public const& _remoteEphemeral, Secret& o_sharedSecret);
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protected:
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KeyPair m_ephemeral; ///< Ephemeral keypair; generated.
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Public m_remoteEphemeral; ///< Public key of remote; parameter.
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};
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/**
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* @brief Secure exchange of static keys.
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* Key exchange is encrypted with public key of remote and then encrypted by block cipher. For a blind remote the ecdhe public key is used to encrypt exchange, and for a known remote the known public key is used. The block cipher key is derived from ecdhe shared secret.
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*
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* Usage: Agree -> Exchange -> Authenticate
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*/
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class ECDHEKeyExchange: private ECDHE
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{
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public:
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/// Exchange with unknown remote (pass public key for ingress exchange)
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ECDHEKeyExchange(Alias& _k): m_alias(_k) {};
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/// Exchange with known remote
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ECDHEKeyExchange(Alias& _k, AliasSession _known): m_alias(_k), m_known(_known) {};
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/// Provide public key for dh agreement to generate shared secret.
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void agree(Public const& _remoteEphemeral);
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/// @returns encrypted payload of key exchange
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void exchange(bytes& o_exchange);
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/// Decrypt payload, check mac, check trust, decrypt exchange, authenticate exchange, verify version, verify signature, and if no failure occurs, update or creats trust and derive session-shared-secret.
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bool authenticate(bytes _exchangeIn);
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private:
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Secret m_ephemeralSecret;
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Alias m_alias;
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AliasSession m_known;
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Secret m_sharedAliasSecret;
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FixedHash<16> m_sharedC;
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FixedHash<16> m_sharedM;
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};
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}
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}
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