elliptic_em_common.cpp

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#include <fc/crypto/base58.hpp>
#include <fc/crypto/elliptic.hpp>
#include <fc/crypto/elliptic_em.hpp>
#include <fc/io/raw.hpp>
#include <fc/crypto/hmac.hpp>
#include <fc/crypto/openssl.hpp>
#include <fc/crypto/ripemd160.hpp>
 
#ifdef _WIN32
# include <malloc.h>
#elif defined(__FreeBSD__)
# include <stdlib.h>
#else
# include <alloca.h>
#endif
 
/* stuff common to all ecc implementations */
 
#define BTC_EXT_PUB_MAGIC   (0x0488B21E)
#define BTC_EXT_PRIV_MAGIC  (0x0488ADE4)
 
namespace fc { namespace em {
 
    namespace detail {
        typedef fc::array<char,37> chr37;
 
        fc::sha256 _left( const fc::sha512& v )
        {
            fc::sha256 result;
            memcpy( result.data(), v.data(), 32 );
            return result;
        }
 
        fc::sha256 _right( const fc::sha512& v )
        {
            fc::sha256 result;
            memcpy( result.data(), v.data() + 32, 32 );
            return result;
        }
 
        static void _put( unsigned char** dest, unsigned int i)
        {
            *(*dest)++ = (i >> 24) & 0xff;
            *(*dest)++ = (i >> 16) & 0xff;
            *(*dest)++ = (i >>  8) & 0xff;
            *(*dest)++ =  i        & 0xff;
        }
 
 
        static chr37 _derive_message( char first, const char* key32, int i )
        {
            chr37 result;
            unsigned char* dest = (unsigned char*) result.begin();
            *dest++ = first;
            memcpy( dest, key32, 32 ); dest += 32;
            _put( &dest, i );
            return result;
        }
 
        chr37 _derive_message( const public_key_data& key, int i )
        {
            return _derive_message( *key.begin(), key.begin() + 1, i );
        }
 
 
        const ec_group& get_curve()
        {
            static const ec_group secp256k1( EC_GROUP_new_by_curve_name( NID_secp256k1 ) );
            return secp256k1;
        }
 
        static private_key_secret _get_curve_order()
        {
            const ec_group& group = get_curve();
            bn_ctx ctx(BN_CTX_new());
            ssl_bignum order;
            FC_ASSERT( EC_GROUP_get_order( group, order, ctx ) );
            private_key_secret bin;
            FC_ASSERT( BN_num_bytes( order ) == static_cast<int>(bin.data_size()) );
            FC_ASSERT( BN_bn2bin( order, (unsigned char*) bin.data() ) == static_cast<int>(bin.data_size()) );
            return bin;
        }
 
        const private_key_secret& get_curve_order()
        {
            static private_key_secret order = _get_curve_order();
            return order;
        }
 
        static private_key_secret _get_half_curve_order()
        {
            const ec_group& group = get_curve();
            bn_ctx ctx(BN_CTX_new());
            ssl_bignum order;
            FC_ASSERT( EC_GROUP_get_order( group, order, ctx ) );
            BN_rshift1( order, order );
            private_key_secret bin;
            FC_ASSERT( BN_num_bytes( order ) == static_cast<int>(bin.data_size()) );
            FC_ASSERT( BN_bn2bin( order, (unsigned char*) bin.data() ) == static_cast<int>(bin.data_size()) );
            return bin;
        }
 
        const private_key_secret& get_half_curve_order()
        {
            static private_key_secret half_order = _get_half_curve_order();
            return half_order;
        }
    }
 
    public_key public_key::from_key_data( const public_key_data &data ) {
        return public_key(data);
    }
 
    private_key private_key::child( const fc::sha256& offset )const
    {
       fc::sha256::encoder enc;
       fc::raw::pack( enc, get_public_key() );
       fc::raw::pack( enc, offset );
       return generate_from_seed( get_secret(), enc.result() );
    }
 
    std::string public_key::to_base58( const public_key_data &key )
    {
      uint32_t check = (uint32_t)sha256::hash(key.data, sizeof(key))._hash[0];
      static_assert(sizeof(key) + sizeof(check) == 37, ""); // hack around gcc bug: key.size() should be constexpr, but isn't
      array<char, 37> data;
      memcpy(data.data, key.begin(), key.size());
      memcpy(data.begin() + key.size(), (const char*)&check, sizeof(check));
      return fc::to_base58(data.begin(), data.size(), fc::yield_function_t());
    }
 
    public_key public_key::from_base58( const std::string& b58 )
    {
        array<char, 37> data;
        size_t s = fc::from_base58(b58, (char*)&data, sizeof(data) );
        FC_ASSERT( s == sizeof(data) );
 
        public_key_data key;
        uint32_t check = (uint32_t)sha256::hash(data.data, sizeof(key))._hash[0];
        FC_ASSERT( memcmp( (char*)&check, data.data + sizeof(key), sizeof(check) ) == 0 );
        memcpy( (char*)key.data, data.data, sizeof(key) );
        return from_key_data(key);
    }
 
    unsigned int public_key::fingerprint() const
    {
        public_key_data key = serialize();
        ripemd160 hash = ripemd160::hash( sha256::hash( key.begin(), key.size() ) );
        unsigned char* fp = (unsigned char*) hash._hash;
        return (fp[0] << 24) | (fp[1] << 16) | (fp[2] << 8) | fp[3];
    }
 
    bool public_key::is_canonical( const compact_signature& c ) {
        return !(c.data[1] & 0x80)
               && !(c.data[1] == 0 && !(c.data[2] & 0x80))
               && !(c.data[33] & 0x80)
               && !(c.data[33] == 0 && !(c.data[34] & 0x80));
    }
 
    private_key private_key::generate_from_seed( const fc::sha256& seed, const fc::sha256& offset )
    {
        ssl_bignum z;
        BN_bin2bn((unsigned char*)&offset, sizeof(offset), z);
 
        ec_group group(EC_GROUP_new_by_curve_name(NID_secp256k1));
        bn_ctx ctx(BN_CTX_new());
        ssl_bignum order;
        EC_GROUP_get_order(group, order, ctx);
 
        // secexp = (seed + z) % order
        ssl_bignum secexp;
        BN_bin2bn((unsigned char*)&seed, sizeof(seed), secexp);
        BN_add(secexp, secexp, z);
        BN_mod(secexp, secexp, order, ctx);
 
        fc::sha256 secret;
        FC_ASSERT(BN_num_bytes(secexp) <= int64_t(sizeof(secret)));
        auto shift = sizeof(secret) - BN_num_bytes(secexp);
        BN_bn2bin(secexp, ((unsigned char*)&secret)+shift);
        return regenerate( secret );
    }
 
    fc::sha256 private_key::get_secret( const EC_KEY * const k )
    {
       if( !k )
       {
          return fc::sha256();
       }
 
       fc::sha256 sec;
       const BIGNUM* bn = EC_KEY_get0_private_key(k);
       if( bn == NULL )
       {
         FC_THROW_EXCEPTION( exception, "get private key failed" );
       }
       int nbytes = BN_num_bytes(bn);
       BN_bn2bin(bn, &((unsigned char*)&sec)[32-nbytes] );
       return sec;
    }
 
    private_key private_key::generate()
    {
       EC_KEY* k = EC_KEY_new_by_curve_name( NID_secp256k1 );
       if( !k ) FC_THROW_EXCEPTION( exception, "Unable to generate EC key" );
       if( !EC_KEY_generate_key( k ) )
       {
          FC_THROW_EXCEPTION( exception, "ecc key generation error" );
 
       }
 
       return private_key( k );
    }
 
 
}
 
void to_variant( const em::private_key& var,  variant& vo )
{
    vo = var.get_secret();
}
 
void from_variant( const variant& var,  em::private_key& vo )
{
    fc::sha256 sec;
    from_variant( var, sec );
    vo = em::private_key::regenerate(sec);
}
 
void to_variant( const em::public_key& var,  variant& vo )
{
    vo = var.serialize();
}
 
void from_variant( const variant& var,  em::public_key& vo )
{
    em::public_key_data dat;
    from_variant( var, dat );
    vo = em::public_key(dat);
}
 
}