Is there a specific sample code of using recover_key()? I got an error with recover_key() in contract.

string msg="charlie";
checksum256 m_hash;
sha256( const_cast<char*>(msg.c_str()), msg.length(), &m_hash );
char* pub;
string sig="SIG_K1_K5cpBg7XHRfgdedEAR9w74bXQZk4TUQk9QDMfzNbttY3eZ5WhmpNuWKiRyidskkdjBH9L9pKKe29RiiELNLCNYzFtFyTqJ";

Error Information:

assert_exception: Assert Exception
w < count():
thread-0  static_variant.hpp:339 set_which
Error unpacking field _storage
thread-0  raw.hpp:368 operator()
error unpacking fc::crypto::signature
thread-0  raw.hpp:616 unpack
  • Can u give me a example about how you call ecverify action by cleos? Thanks!!
    – Vitor
    Jan 12, 2019 at 11:39

2 Answers 2


Here's one way of doing it:

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

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

  ///@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));

EOSIO_ABI( ec, (ecverify) )
void assert_recover_key2(const checksum256* digest, const signature* sig, const eosio::public_key* pub) {
     public_key pub2;
     pub2.data[0] = char(pub->type.value);
     memcpy(&pub2.data[1], pub->data.data(), 33);
     assert_recover_key(digest, (const char*)sig, sizeof(signature), (const char*)&pub2, sizeof(public_key));


that's my code, take care the public_key and eosio::public_key is not same

  • what's the format of sig? my signature is string like "SIG_K1_K5cpBg7XHRfgdedEAR9w74bXQZk4TUQk9QDMfzNbttY3eZ5WhmpNuWKiRyidskkdjBH9L9pKKe29RiiELNLCNYzFtFyTqJ",How to converto to signature type? Aug 15, 2018 at 6:00
  • @BruceLingKing just pass the string in your action, and eos will convert it to eosio::public_key directly
    – Jimmy Guo
    Aug 15, 2018 at 7:01
  • I did it as u said .But when send action,the errors occured "Error: Non-base58 character order.sig = "SIG_K1_K5cpBg7XHRfgdedEAR9w74bXQZk4TUQk9QDMfzNbttY3eZ5WhmpNuWKiRyidskkdjBH9L9pKKe29RiiELNLCNYzFtFyTqJ"" Aug 15, 2018 at 7:20
  • According to my test, assert_recover_key2 would failed!When I modify it as bellow,it success. assert_recover_key(digest, (const char*)sig, sizeof(signature), (const char*)&(pub2.data), sizeof(public_key)); Aug 15, 2018 at 10:48
  • @BruceLingKing any difference with &pub2.data and &pub2?
    – Jimmy Guo
    Aug 15, 2018 at 11:50

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