#420 - recover function for sign transaction

libraries/plugins/peerplays_sidechain/ethereum/transaction.cpp

@@ -129,6 +129,40 @@ void raw_transaction::deserialize(const std::string &raw_tx) {
 
 //! signed_transaction
 
+std::string signed_transaction::recover(const std::string &chain_id) const {
+   fc::ecc::compact_signature input64;
+   fc::from_hex(r, (char *)&input64.at(1), 32);
+   fc::from_hex(v, (char *)&input64.at(0), 1);
+   int recid = input64.at(0) - from_hex<int>(chain_id) * 2 - 35;
+   fc::from_hex(s, (char *)&input64.at(33), 32);
+
+   secp256k1_ecdsa_recoverable_signature sig;
+   FC_ASSERT(secp256k1_ecdsa_recoverable_signature_parse_compact(eth_context(), &sig, (const unsigned char *)&input64.data[1], recid));
+
+   raw_transaction tr;
+   tr.nonce = nonce;
+   tr.gas_price = gas_price;
+   tr.gas_limit = gas_limit;
+   tr.to = to;
+   tr.value = value;
+   tr.data = data;
+   tr.chain_id = chain_id;
+
+   secp256k1_pubkey rawPubkey;
+   FC_ASSERT(secp256k1_ecdsa_recover(eth_context(), &rawPubkey, &sig, (const unsigned char *)tr.hash().data()));
+
+   std::array<uint8_t, 65> pubkey;
+   size_t biglen = 65;
+   FC_ASSERT(secp256k1_ec_pubkey_serialize(eth_context(), pubkey.data(), &biglen, &rawPubkey, SECP256K1_EC_UNCOMPRESSED));
+
+   const std::string out = std::string(pubkey.begin(), pubkey.end()).substr(1);
+   bytes hash;
+   hash.resize(32);
+   keccak_256((const unsigned char *)out.data(), out.size(), (unsigned char *)hash.data());
+
+   return add_0x(fc::to_hex((char *)&hash[0], hash.size()).substr(24));
+}
+
 std::string signed_transaction::serialize() const {
    rlp_encoder encoder;
    const std::string serialized = encoder.encode(remove_0x(nonce)) +

libraries/plugins/peerplays_sidechain/include/graphene/peerplays_sidechain/ethereum/transaction.hpp

@@ -55,6 +55,8 @@ public:
    std::string r;
    std::string s;
 
+   std::string recover(const std::string &chain_id) const;
+
    virtual std::string serialize() const override;
    virtual void deserialize(const std::string &raw_tx) override;
 };