The Poem of Knowledge

Description

CTF: Whitehacks 2022

Author: xbowery

Difficulty: Easy

Our knowledgeable alien friend named Beale left us with a purported “Poem of Knowledge” before he went back to his universe.

He also dropped a message behind. Can you decipher what he was trying to say?

17-73-24-55-84-101-141-44-54-49-10-123-62-131-114-67-47-46-60-83-84

Note: Please wrap the flag with WH2022{...} The flag is case-sensitive!

Poem

Solution

Pwned by @skytect

We get a text:

The Road Not Taken
By Robert Frost

Two roads diverged in a yellow wood,
And sorry I could not travel both
And be one traveler, long I stood
And looked down one as far as I could
To where it bent in the undergrowth;

Then took the other, as just as fair,
And having perhaps the better claim,
Because it was grassy and wanted wear;
Though as for that the passing there
Had worn them really about the same,

And both that morning equally lay
In leaves no step had trodden black.
Oh, I kept the first for another day!
Yet knowing how way leads on to way,
I doubted if I should ever come back.

I shall be telling this with a sigh
Somewhere ages and ages hence:
Two roads diverged in a wood, and I—
I took the one less traveled by,
And that has made all the difference.

And something that looks like a ciphertext:

17-73-24-55-84-101-141-44-54-49-10-123-62-131-114-67-47-46-60-83-84

Our knowledgeable alien friend named Beale

This gives us a hint. If we google beale crypto, we’ll find the Beale ciphers, which use the numbers to lookup words in the text and uses the first letter of each word accordingly.

We can write a simple script to help us decode this:

import re

key = """The Road Not Taken
By Robert Frost

Two roads diverged in a yellow wood,
And sorry I could not travel both
And be one traveler, long I stood
And looked down one as far as I could
To where it bent in the undergrowth;

Then took the other, as just as fair,
And having perhaps the better claim,
Because it was grassy and wanted wear;
Though as for that the passing there
Had worn them really about the same,

And both that morning equally lay
In leaves no step had trodden black.
Oh, I kept the first for another day!
Yet knowing how way leads on to way,
I doubted if I should ever come back.

I shall be telling this with a sigh
Somewhere ages and ages hence:
Two roads diverged in a wood, and I—
I took the one less traveled by,
And that has made all the difference."""
ciphertext = "17-73-24-55-84-101-141-44-54-49-10-123-62-131-114-67-47-46-60-83-84"

key = re.sub(r'[^a-zA-Z\s\n]', '', key)  # remove everything that's not a letter, space, or newline
key = re.sub(r'[\s\n]+', ' ', key)  # replace multiple spaces and newlines with single spaces
key = key.split(' ')

ciphertext = [int(i) for i in ciphertext.split('-')]  # 17 73 24 55 84 101 141 44 54 49 10 123 62 131 114 67 47 46 60 83 84
ciphertext = [key[i-1][0] for i in ciphertext]
print(''.join(ciphertext))  # WH2022{IHopeYouhadagreattime}

WH2022{IHopeYouhadagreattime}