Mastering Reverse Engineering

Bitwise algebra

Boolean algebra or bitwise operations are necessary in low-level programming since it can perform simple calculations by changing the bits of a number. It is commonly used in cryptography's obfuscation and decoding.

NOT

This operation reverses the bits.

Consider the following as an example: NOT AL

If AL equals 1010101b (55h), it becomes 10101010b (AAh).

AND

This operation sets bit to 1 if both are 1s, otherwise it sets bit to 0.

Consider the following as an example: AND AL, AH

If AL equals 10111010b (BAh) and AH equals 11101101b (EDh), AL becomes 10101000b (A8h).

OR

This operation sets bit to 0 if both are 0s, else it sets bit to 1.

Consider the following as an example: OR AL, AH

If AL equals 10111010b (BAh) and AH equals ...