Hello, Paul. Here i send you test message. Also i send you two different messages, one with .zip file and one with .rar. Actually, here i want to say few things i thought about after i finished coding. I made my class working with uint8_t type - byte arrays. But then i thought it should be working the same way with any int type actually.. And even with any data if we think of it as a simple sequence of bytes. But here i came to the problem: 1. i can replace uint8_t by template class and then use cast in process() method to get data in byte representation: byte *bytes = reinterpet_cast<byte*>(&in_data) and then just deal with byte sequence. 2. or remove vector from member and treat any structure as sequence of bytes. But the thing is - we need checksum for data stored in structure of checksum for structure itself? Because if we take complex structure(something like map<pair<set<int>,pair<int,string> > >) what checksum are we calculating actually? Thank you! -- Alexandr mailto:daywalker@mail333.com