Timing Attack for Password Cracking in Python: Last Digit Not Correct

Question

I'm working on a timing attack to crack a password using Python. My goal is to measure the time it takes to check each digit of the password and use this information to deduce the correct digits. The code mostly works, but I often find that the last digit is not correct. Here is the code I have so far:

import time

real_password = "7090"

def check_password(password): # Don't change
if len(password) != len(real_password):
return False
for x, y in zip(password, real_password):
time.sleep(0.1) # Simulates the wait time of the safe's mechanism
if int(x) != int(y):
return False
return True

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Complete code in comments

Answer 1

def crack_password():
password = ["0"] * len(real_password)

for i in range(len(real_password)):
max_time = 0
correct_digit = 0
for digit in range(10):
password[i] = str(digit)
start_time = time.perf_counter()
check_password("".join(password))
end_time = time.perf_counter()

elapsed_time = end_time - start_time

# Compare the elapsed time to find the maximum
if elapsed_time > max_time:
max_time = elapsed_time
correct_digit = digit

# Set the found correct digit
password[i] = str(correct_digit)

return "". join(password)

print(crack_password())

QUESTIONS:
1. Why might the last digit not be correct in this timing attack?
2. How can I improve the accuracy of my timing measurements to ensure the correct password is found?

Any help or suggestions would be greatly appreciated. Thanks!