Recently, I’m reading pediy’s book: Encryption and Decryption. This is a really good book with many practical technologies and skills, and it’s also very interesting. In Chapter 2, I met a problem, so I cracked the demo crack-me program with ollydbg, but I’m not satisfied with that, so I studied the encrytion algorithm and wrote a keygen program.

The main algorithm is very simple, but it took me a lot of time to deal with the multi-byte characters problems, and I found there is another defination of unicode on Microsoft’s platform! I can’t figure out why Micro$oft didn’t use UTF-8 to build his system just like Macintosh, because with UTF-8, we programmers don’t have to deal with these troubles at all. Anyway, Windows is such a snorty that most people still have to use it.

Here is the main code:

cpp My First Keygen void CCrackMeKeygenDlg::OnOK() { USES_CONVERSION; UpdateData(TRUE); WCHAR *user_name; user_name = T2W((LPCTSTR)m_username); int m[8] = {0x0C, 0x0A, 0x13, 0x09, 0x0C, 0x0B, 0x0A, 0x08}; unsigned i = 3, j = 0; int ans = 0; if (wcslen(user_name) < 5) { MessageBox(_T("Username should be at least 5 characters.")); return; } for (; i < wcslen(user_name); ++i, ++j) { if (j > 7) { j = 0; } ans += m[j] * ((BYTE)user_name[i]); } TCHAR res[1000]; wsprintf(res, _T("%ld"), ans); m_serialnumber = res; m_author = _T("Created by Leon.\nhttp://leons.im"); UpdateData(FALSE); //CDialog::OnOK(); }