Reverse Engineering for Beginners

CHAPTER 19. MANIPULATING SPECIFIC BIT(S) CHAPTER 19. MANIPULATING SPECIFIC BIT(S)

OllyDbg

Let’s try this example in OllyDbg. First, let’s see the binary form of the constants we are going to use:

0x200(0000000000000000000 1 000000000) (i.e., the 10th bit (counting from 1st)).

Inverted0x200is0xFFFFFDFF(1111111111111111111 0 111111111).

0x4000(00000000000000 1 00000000000000) (i.e., the 15th bit).

The input value is:0x12340678(10010001101000000011001111000). We see how it’s loaded:

Figure 19.1:OllyDbg: value is loaded intoECX