PicoCTF-2022 Writeup
  • README
  • Binary Exploitation
    • buffer overflow 1
    • buffer overflow 2
    • buffer overflow 3
    • flag leak
    • function overwrite
    • ropfu
    • stack cache
    • x-sixty-what
  • Cryptography
    • basic-mod1
    • basic-mod2
    • diffie-hellman
    • morse-code
    • NSA Backdoor
    • Sequences
    • substitution
    • Sum-O-Primes
    • Very Smooth
  • Forensics
    • Operation Oni
    • Operation Orchid
    • SideChannel
    • St3g0
    • Torrent Analyze
  • Reverse Engineering
    • Bbbbloat
    • Keygenme
    • unpackme
    • Wizardlike
  • Web Exploitation
    • Forbidden Paths
    • noted
    • Roboto Sans
    • SQLiLite
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  1. Cryptography

basic-mod2

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Last updated 3 years ago

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Challenge

A new modular challenge! Download the message . 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. Wrap your decrypted message in the picoCTF flag format (i.e. picoCTF{decrypted_message})

Solution

Run the solution , which directly applies the operations as per the challenge description.

Flag

picoCTF{1NV3R53LY_H4RD_C680BDC1}

here
script.py