Function at 0x420550
Capabilities:
Validate payment card number using luhn algorithm

Disassembly:
push ebx
push ebp
push esi
mov esi, dword [esp + 0x14]
mov al, byte [esi]
test al, al
push edi
je 0x4208eb
cmp al, 0x25
jne 0x4208d1
push 3
add esi, 1
push 0x4a0b0c
push esi
call fcn.0048838a
add esp, 0xc
test eax, eax
jne 0x420691
movsx eax, byte [esi + 3]
add esi, 3
sub eax, 0x25
add esi, 1
cmp eax, 0x4d
ja case.default.0x420870
movzx eax, byte [eax + 0x42090c]
jmp dword [eax*4 + 0x4208fc]
mov ecx, dword [esp + 0x1c]
mov al, byte [ecx + 1]
add ecx, 1
test al, al
je 0x4208e1
mov edx, dword [esp + 0x14]
nop
add ecx, 1
mov byte [edx], al
mov al, byte [ecx]
add edx, 1
test al, al
jne 0x4205c0
mov dword [esp + 0x14], edx
jmp 0x4208e1
mov cl, byte [esi]
xor eax, eax
cmp cl, 0x30
jl 0x4205f9
cmp cl, 0x39
jg 0x4205f9
lea edx, [eax + eax*4]
add esi, 1
movsx eax, cl
mov cl, byte [esi]
cmp cl, 0x30
lea eax, [eax + edx*2 - 0x30]
jge 0x4205e0
mov edx, dword [esp + 0x1c]
add edx, 1
test eax, eax
je 0x42061f
mov edi, dword [esp + 0x14]
mov cl, byte [edx]
test cl, cl
je 0x42061b
mov byte [edi], cl
add edi, 1
add edx, 1
sub eax, 1
jne 0x420608
mov dword [esp + 0x14], edi
cmp byte [esi], 0x25
je 0x4208de
pop edi
pop esi
pop ebp
xor al, al
pop ebx
ret
mov al, byte [esi]
xor edi, edi
cmp al, 0x30
jl 0x42064e
cmp al, 0x39
jg 0x42064e
add esi, 1
movsx edx, al
mov al, byte [esi]
cmp al, 0x30
lea ecx, [edi + edi*4]
lea edi, [edx + ecx*2 - 0x30]
jge 0x420637
mov ebx, dword [esp + 0x1c]
lea eax, [ebx + 1]
push eax
call dword [sym.imp.KERNEL32.dll_lstrlenA]
cmp eax, edi
jge 0x420662
mov edi, eax
sub eax, edi
test edi, edi
lea ecx, [eax + ebx + 1]
je 0x420687
mov edx, dword [esp + 0x14]
mov al, byte [ecx]
test al, al
je 0x420683
mov byte [edx], al
add edx, 1
add ecx, 1
sub edi, 1
jne 0x420670
mov dword [esp + 0x14], edx
cmp byte [esi], 0x25
jne case.default.0x420870
jmp 0x4208de
mov al, byte [esi]
cmp al, 0x70
je 0x42069b
cmp al, 0x50
jne case.default.0x420870
movsx eax, byte [esi + 1]
add esi, 1
sub eax, 0x31
js case.default.0x420870
cmp eax, 9
jg case.default.0x420870
mov ecx, dword [esp + 0x1c]
mov ebp, dword [ecx + eax*4 + 0x48]
movsx eax, byte [esi + 1]
add esi, 1
sub eax, 0x25
add esi, 1
cmp eax, 0x50
ja case.default.0x420870
movzx edx, byte [eax + 0x42096c]
jmp dword [edx*4 + 0x42095c]
mov al, byte [esi]
xor ecx, ecx
cmp al, 0x30
jl 0x4206fb
cmp al, 0x39
jg 0x4206fb
add esi, 1
movsx edx, al
mov al, byte [esi]
cmp al, 0x30
lea ecx, [ecx + ecx*4]
lea ecx, [edx + ecx*2 - 0x30]
jge 0x4206e4
lea eax, [ecx - 1]
cmp eax, 8
ja case.default.0x420870
jmp dword [eax*4 + 0x4209c0]
mov ecx, 0xa
jmp 0x42074b
mov ecx, 0x64
jmp 0x42074b
mov ecx, 0x3e8
jmp 0x42074b
mov ecx, 0x2710
jmp 0x42074b
mov ecx, 0x186a0
jmp 0x42074b
mov ecx, 0xf4240
jmp 0x42074b
mov ecx, 0x989680
jmp 0x42074b
mov ecx, 0x5f5e100
jmp 0x42074b
mov ecx, 0x3b9aca00
cmp ebp, ecx
jl 0x420756
mov eax, ebp
cdq
idiv ecx
mov ebp, edx
mov eax, 0x66666667
imul ecx
sar edx, 2
mov ecx, edx
shr ecx, 0x1f
add ecx, edx
cmp byte [esi], 0x25
jne case.default.0x420870
add esi, 1
test ecx, ecx
je 0x4208e1
jmp 0x420780
mov eax, ebp
cdq
idiv ecx
mov ebx, eax
mov eax, 0x66666667
imul ecx
sar edx, 2
mov eax, edx
shr eax, 0x1f
add bl, 0x30
add eax, edx
mov ecx, eax
jne 0x420780
mov ecx, dword [esp + 0x14]
mov byte [ecx], bl
jmp 0x4208e1
mov al, byte [esi]
xor ecx, ecx
cmp al, 0x30
jl 0x4207c9
cmp al, 0x39
jg 0x4207c9
add esi, 1
movsx edx, al
mov al, byte [esi]
cmp al, 0x30
lea ecx, [ecx + ecx*4]
lea ecx, [edx + ecx*2 - 0x30]
jge 0x4207b2
lea eax, [ecx - 1]
cmp eax, 8
ja case.default.0x420870
jmp dword [eax*4 + 0x4209e4]
mov ecx, 0xa
jmp 0x420819
mov ecx, 0x64
jmp 0x420819
mov ecx, 0x3e8
jmp 0x420819
mov ecx, 0x2710
jmp 0x420819
mov ecx, 0x186a0
jmp 0x420819
mov ecx, 0xf4240
jmp 0x420819
mov ecx, 0x989680
jmp 0x420819
mov ecx, 0x5f5e100
jmp 0x420819
mov ecx, 0x3b9aca00
cmp ebp, ecx
jl 0x420756
mov eax, 0x66666667
imul ebp
sar edx, 2
mov eax, edx
shr eax, 0x1f
add eax, edx
mov ebp, eax
cmp ebp, ecx
jge 0x420821
jmp 0x420756
test ebp, ebp
mov ecx, ebp
je 0x42085f
xor edi, edi
mov eax, 0x66666667
imul ecx
sar edx, 2
mov ecx, edx
shr ecx, 0x1f
add ecx, edx
add edi, 1
test ecx, ecx
jne 0x420845
jmp 0x420864
mov edi, 1
lea eax, [edi - 1]
cmp eax, 8
ja case.default.0x420870
jmp dword [eax*4 + 0x420a08]
mov ecx, 1
jmp 0x420780
mov ecx, 0xa
jmp 0x420780
mov ecx, 0x64
jmp 0x420780
mov ecx, 0x3e8
jmp 0x420780
mov ecx, 0x2710
jmp 0x420780
mov ecx, 0x186a0
jmp 0x420780
mov ecx, 0xf4240
jmp 0x420780
mov ecx, 0x989680
jmp 0x420780
mov ecx, 0x5f5e100
jmp 0x420780
mov ecx, dword [esp + 0x14]
mov byte [ecx], al
add ecx, 1
mov dword [esp + 0x14], ecx
add esi, 1
mov al, byte [esi]
test al, al
jne 0x420562
mov edx, dword [esp + 0x14]
pop edi
pop esi
pop ebp
mov byte [edx], 0
mov al, 1
pop ebx
ret