27 lines
777 B
Python
27 lines
777 B
Python
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#!/usr/bin/env python3
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# Take each number mod 41 and find the modular inverse for the result. Then map to the following character set: 1-26 are the alphabet, 27-36 are the decimal digits, and 37 is an underscore.
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with open('message.txt') as file:
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content = file.read().strip()
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print("picoCTF{", end="")
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for n in content.split(' '):
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number = int(n)
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number %= 41
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# NOTE: modular inverse
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number = pow(number, -1, 41)
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if number >=1 and number < 27:
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print(chr(number - 1 + ord('A')), end="")
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elif number >= 27 and number < 37:
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print(number - 27, end="")
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elif number == 37:
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print('_', end="")
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else:
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print()
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print(f"Code author seems to have forgotten a number.... {number}")
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exit(1)
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print("}")
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