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@ -44,62 +44,3 @@ void ECDHE::agree(Public const& _remote, Secret& o_sharedSecret) const |
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s_secp256k1.agree(m_ephemeral.sec(), m_remoteEphemeral, o_sharedSecret); |
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} |
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void ECDHEKeyExchange::agree(Public const& _remoteEphemeral) |
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{ |
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s_secp256k1.agree(m_ephemeral.sec(), _remoteEphemeral, m_ephemeralSecret); |
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} |
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void ECDHEKeyExchange::exchange(bytes& o_exchange) |
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{ |
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if (!m_ephemeralSecret) |
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// didn't agree on public remote
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BOOST_THROW_EXCEPTION(InvalidState()); |
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// The key exchange payload is in two parts and is encrypted
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// using ephemeral keypair.
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//
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// The first part is the 'prefix' which is a zero-knowledge proof
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// allowing the remote to resume or emplace a previous session.
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// If a session previously exists:
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// prefix is sha3(token) // todo: ephemeral entropy from both sides
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// If a session doesn't exist:
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// prefix is sha3(m_ephemeralSecret)
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//
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// The second part is encrypted using the public key which relates to the prefix.
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Public encpk = m_known.first ? m_known.first : m_remoteEphemeral; |
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bytes exchange(encpk.asBytes()); |
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// This is the public key which we would like the remote to use,
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// which maybe different than the previously-known public key.
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//
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// Here we should pick an appropriate alias or generate a new one,
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// but for now, we use static alias passed to constructor.
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//
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Public p = toPublic(m_alias.m_secret); |
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exchange.resize(exchange.size() + sizeof(p)); |
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memcpy(&exchange[exchange.size() - sizeof(p)], p.data(), sizeof(p)); |
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// protocol parameters; should be fixed size
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bytes v(1, 0x80); |
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exchange.resize(exchange.size() + v.size()); |
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memcpy(&exchange[exchange.size() - v.size()], v.data(), v.size()); |
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h256 auth; |
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sha3mac(m_alias.m_secret.ref(), m_ephemeralSecret.ref(), auth.ref()); |
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Signature sig = s_secp256k1.sign(m_alias.m_secret, auth); |
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exchange.resize(exchange.size() + sizeof(sig)); |
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memcpy(&exchange[exchange.size() - sizeof(sig)], sig.data(), sizeof(sig)); |
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aes::AuthenticatedStream aes(aes::Encrypt, m_ephemeralSecret, 0); |
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h256 prefix(sha3(m_known.second ? m_known.second : (h256)m_remoteEphemeral)); |
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aes.update(prefix.ref()); |
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s_secp256k1.encrypt(encpk, exchange); |
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aes.update(&exchange); |
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aes.streamOut(o_exchange); |
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} |
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