How to find reverse of pow(a,b,c) in python?

Question

pow(a,b,c) operator in python returns (a**b)%c . If I have values of b, c, and the result of this operation (res=pow(a,

Answer 1

The best you can do is something like this:

a = 12
b = 5
c = 125

def is_int(a):
    return a - int(a) <= 1e-5

# ============= Without C ========== #
print("Process without c")
rslt = pow(a, b)

print("a**b:", rslt)

print("a:", pow(rslt, (1.0 / b)))

# ============= With C ========== #
print("\nProcess with c")
rslt = pow(a, b, c)

i = 0
while True:

    a = pow(rslt + i*c, (1.0 / b))

    if is_int(a):
        break
    else:
        i += 1

print("a**b % c:", rslt)
print("a:", a)

You can never be sure that you have found the correct modulo value, it is the first value that is compatible with your settings. The algorithm is based on the fact that a, b and c are integers. If they are not you have no solution a likely combination that was the original one.

Outputs:

Process without c
a**b: 248832
a: 12.000000000000002

Process with c
a**b % c: 82
a: 12.000000000000002