Well, the criptos can use 256bits, so BINARY(32) resolves to store, the same c++ code do to store on LevelDB blockchain. But.. if the problem is only to store this is OK. The real problem is to do the calcs (SUM p example) inside SQL. If you use a program, so there are libraries do work with large numeric data types as uint256. Study if DECIMAL(27,18) will be OK to your case. I dont know an easy way to proccess the calcs inside SQL with number with 256b at the moment. On SQL Server is possible to create programs on .NET so you can program some aritmetic works inside SQL SERVER, to your BINARY(32) data, the same is possible on Firebird with external FUNCTIONS. Maybe the easiest way is to do by program.