Cheat Engine

[dick_traced]

Assume i want to change some opcodes in a program
the program has a crc check which i can't find
how can i change the eip to redirect to a memory region that isn't monitorised, and there put my modified instructions? and how to change back the eip to allow the program to continue from where i modified the opcode
or how's the trick of changing the eip?
how can this be accomplished with cheatengine?

practical example:

401234: sub eax,ecx

I want to patch to 'add eax,ecx' without failing the crc check

[Dark Byte]

you allocate some memory
there you write:

[sullx]

Ok I have been experimenting all evening trying to change the eip to point to some code I have injected in to memory 'outside' the game memory. I believe I am understanding how to change eip (right click the memory address -> Change register at this location -> enter memory address where I allocated some memory for my code. But what I don't understand is how to allocate memory outside the game memory region (in other words, outside the space monitored by the crc/integrity check). I tried using cheat engine to allocate memory while attached to a different application, and then used the memory address for the eip when attached to the program of interest, but that did not work.

So, how does one allocate memory outside of the game's memory region in cheat engine and add code to that region for use with a change of the eip register? Thanks

[Dark Byte]

You just use cheat engine to allocate the memory, but did you initialize the memory you allocated and jump back to the instruction AFTER your hook ?

Else it will be executing random code or will never return and crash then

e.g:

[sullx]

Thank you so much. This worked excellently. For whatever reason, the game has a CRC, but does not have a debugger check. Well I believe that it may, but for whatever reason, CE is not detected on 64 bit by this games anticheat protection.