Hi Eric, As I step through this code, I'm not convinced it's a CRC anymore. CRC may be an 'Windows Myth' (similar to an Urban Myth). I presumed it was a CRC based on grepping the web and usenet.
I'm still part way through my first pass. After a few separate runs, I'll have a better handle. Below is typical of what I am seeing. Are you aware of a checksum which simply 'ADDs' dwords at a time? In the context of 'Check Digits' (not Checksums), this appears to be similar to the IBM Check Digit Scheme, without the weighting... Without source code, there's no telling where this will end up... Pehaps Microsoft Sums diffent Headers and Sections, and then feeds it inot a CRC later. Similar is discussed in ImageGetDigestStream (http://msdn2.microsoft.com/en-us/library/ms680160.aspx). But again, basically undocumented. Jeff 76c94627 0306 add eax,dword ptr [esi] 76c94629 134604 adc eax,dword ptr [esi+4] 76c9462c 134608 adc eax,dword ptr [esi+8] 76c9462f 13460c adc eax,dword ptr [esi+0Ch] 76c94632 134610 adc eax,dword ptr [esi+10h] 76c94635 134614 adc eax,dword ptr [esi+14h] 76c94638 134618 adc eax,dword ptr [esi+18h] 76c9463b 13461c adc eax,dword ptr [esi+1Ch] 76c9463e 134620 adc eax,dword ptr [esi+20h] 76c94641 134624 adc eax,dword ptr [esi+24h] 76c94644 134628 adc eax,dword ptr [esi+28h] 76c94647 13462c adc eax,dword ptr [esi+2Ch] 76c9464a 134630 adc eax,dword ptr [esi+30h] 76c9464d 134634 adc eax,dword ptr [esi+34h] 76c94650 134638 adc eax,dword ptr [esi+38h] 76c94653 13463c adc eax,dword ptr [esi+3Ch] On 6/21/07, Eric Hughes <[EMAIL PROTECTED]> wrote: > At 04:25 PM 6/21/2007, Jeffrey Walton wrote: > >Yes - I think I read elsewhere that this is ZModem and the like, but > >not my Algorithm of interest... > > It's possible to reverse engineer CRC's pretty easily if you've got a CRC > oracle. Just feed it one-word inputs. The linker is such a CRC oracle. > > Eric > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the "Crypto++ Users" Google Group. To unsubscribe, send an email to [EMAIL PROTECTED] More information about Crypto++ and this group is available at http://www.cryptopp.com. -~----------~----~----~----~------~----~------~--~---
