hi everyone!
this is my encryption routine (using standard call) in x86 Assembler

__ASM{

encrypt:
push ebp
mov ebp,esp
mov eax, [ebp+8]
mov ecx, [ebp+12]

push eax
and eax,0xAA
not al
mov edx,eax
pop eax
and eax,0x55
xor ecx,edx
xor ecx,eax
rol cl,1
rol cl,1
mov eax,ecx

sub al,0x20
pop ebp
ret
}

all im trying to do now is Reverse the "encrypt" Algorithms Effect (need to create a DECRYPT routine)
if anyone can help me, it would be much appreciated!
thanks x

ps..if you need any more information, let me know .

Not sure which of the four people from hallam you are but u might wanna be more careful when asking for answers in forums

This appears to be, at first blush, a simple xor substitution/rotation algorithm. Simple stuff. You solve it... If this is from commercial software, I have to think there is more to it than this, unless they are trying for "security by obscurity" - the key is in the "key". If you have the key, and know the algorithm to transform the plain-text, decryption is (at least for symmetric keys) trivial. Read Bruce Schneier's book "Applied Cryptography" if you are interested in this stuff.