Ancient Foreign Communications

Challenge We got word from a friend of ours lost in the depths of the Andorran jungles! Help us figure out what he is trying to tell us before its too late!

Note: The flag here is non-standard, in the result you should end up with some words! The flag is IceCTF{<words, lowercase, including spaces>}

Solution We’re given a file with hex bytes, we can use xxd to covnert that into the appropriate characters/bytes:

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xxd -r -p comms.txt > out.txt

Which is full of some fun symbols?

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⨅]]⌞⌞⌟[⨆]⌟]]]⨆⨆⨆⌜[[[⌝⌝⌝⌞⌝⌝⌝⌝⨆⌝⌝⌝⌞⌞⌝⌝⌝⌝⌟⌝⌝⨅⨅⌞⌞⨆[]]]⌝⌝⌝⌝]]⌟[[[⌝⌝⌝⌝⌟⌝⌝⌝⌝]]]⌞⌞⌞⌝⌝⌝⨆]⌞⌞

combining pigpen cipher with T9 we translate this to:

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⨅ ]] ⌞⌞ ⌟ [ ⨆ ] ⌟ ]]] ⨆⨆⨆ ⌜ [[[ ⌝⌝⌝ ⌞ ⌝⌝⌝⌝ ⨆ ⌝⌝⌝ ⌞⌞ ⌝⌝⌝⌝ ⌟ ⌝⌝ ⨅⨅ ⌞⌞ ⨆ [ ]]] ⌝⌝⌝⌝ ]] ⌟ [[[ ⌝⌝⌝⌝ ⌟ ⌝⌝⌝⌝ ]]] ⌞⌞⌞ ⌝⌝⌝ ⨆ ] ⌞⌞
t h  e  _ m a g _ i   c   w o   r   d s    a r   e  s    _ q  u  e  a m i   s    h  _ o   s    _ s    i   f   r   a g e

method explained:

• ⨅ in pigpen would signify H, when we instead combine this with T9, it would mean the letter t (one press on the number 8)
• ]] would be the dd in classic pigpen, but now signifies 2 presses on the number 4, which would be an h
• ⌞⌞ is two presses on the 3, so a letter e
• etc

This gives us the sentence

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the magic words are squeamish ossifrage

Which was the solution to a challenge ciphertext set by the inventor of RSA in 1977 (link)

Flag

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IceCTF{squeamish ossifrage}

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