CODEWITHSUNDEEP
pythonpython-3.xbit-manipulationbitwise-operatorsbitwise-and
Michael Parkadze
Michael Parkadze

Reputation: 452

Is there a way to reverse this python function?

def function(value):
    bit = value << 1 
    movebit = bit & 255 
    if (value> 127 ):
        movebit = movebit | 1
    return (movebit)

I have got this piece of code that I am trying to reverse so for example I know that the first line is actually to multiply the user_input and save it in bit.

the thing is I can not figure out how to change the next few lines to reverse the output.

example:

test = [226, 3, 214, 111, 20, 240]
# after function => [197, 6, 173, 222, 40, 225]
# goal is to reverse them back to test
toReverse = [197, 6, 173, 222, 40, 225]

my goal is to for loop over toReverse and on each element, send it to the function and get back the number that is on the same index as testArray.

Upvotes: 1

Views: 220

Answers (2)

Tomasz Es
Tomasz Es

Reputation: 1

I created whole decryptor to this task (encryptor) - code you put is a part of it. Check out: https://github.com/sisidor69/CyWar_Decryptor

Upvotes: 0

user3431635
user3431635

Reputation: 380

It seem that function is rotl - rotate left operation. So reverse would be rotr: rotate right:

def rotr(value):
    zbit = (value & 1) << 7
    return (value >> 1) | zbit

Upvotes: 4

Related Questions