- #1
Mc_Topaz
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Homework Statement
At my company we calculate a product's serial number from a MAC address provided with the unit. One of the equations is done with a bitwise AND operation of two integers. I have tried to run that equation backwards but with no result.
Variables and data:
V = The source value to do the bitwise AND operation with
C = A known constant to use in the bitwise AND operation
S = Result of bitwise AND operation
Let say: V = 10, C = 6
Homework Equations
The equation forward is: V & C = S => 10 & 6 = 2
In binary:
1010 = 10
0110 = 6
-----
0010 = 2
Now I just want to reverse that process and calculate 10 from 6 and 2 in some way.
Don't try with: C + 2S (6 + (2*2)) works just in this case.
The Attempt at a Solution
I tried the opposite way by changing V for S:
2 & 6 = 2
In binary:
0010 = 2
0110 = 6
-----
0010 = 2
The problem occurs when one of the bits in the V is 1 and the equivalent bit in C is 0. The bit in S will then be 0 and V's bit can never return to 1.
Any suggestions?
/Mc_Topaz