#include <eosiolib/eosio.hpp>
#include <eosiolib/print.hpp>
#include <eosiolib/crypto.h>

using namespace eosio;

// ...

class ec: public eosio::contract {
  public:
      using contract::contract;

  ///@abi action
  void ecrecover(std::string data, const signature &sig)
  {
    std::string tmp;
    checksum256 digest;
    sha256(&data[0], data.size(), &digest);

    char pub[34]; // public key without checksum
    auto n = recover_key(&digest, (char *)&sig, sizeof(sig), pub, 34);
    assert(n == 34);

    std::string pubhex = to_hex(pub, sizeof(pub)).substr(2); // remove leading '00'
    tmp = hex_to_string(pubhex.c_str());
    strcpy(pub, tmp.c_str());

    checksum160 chksm;
    ripemd160(pub, 33, &chksm);

    tmp = hex_to_string(pubhex + to_hex(&chksm, 20).substr(0,8)); // append checksum

    unsigned char encoded[37  * 137 / 100];
    base58encode(tmp, 37, encoded);
    tmp = "EOS" + std::string(reinterpret_cast<char*>(encoded));
    assert(tmp.length() == 53);
    print(tmp);
  }

  ///@abi action
  void ecverify(std::string data, const signature &sig, const public_key &pk)
  {
    checksum256 digest;
    sha256(&data[0], data.size(), &digest);

    assert_recover_key(&digest, (const char *)&sig, sizeof(sig), (const char *)&pk, sizeof(pk));
    print("VALID");
  }
};

EOSIO_ABI( ec, (ecrecover)(ecverify) )