Description
This challenge promises that nothing is hidden: the flag is 'in-the-clear.' Your only task is to retrieve the file from the challenge server and read it.
Setup
Download the file from the challenge page.
wget <challenge_url>/nothing_up_my_sleeveSolution
Want to try it yourself first?
The guided walkthrough reveals hints one step at a time.
Step 1
Download and read the fileObservationThe challenge description explicitly stated the flag is 'in-the-clear,' which meant no encoding or obfuscation was involved and suggested that simply downloading the file and printing it with cat would be sufficient.Use wget (or curl) to download the file from the URL provided on the challenge page, then print its contents with cat. The flag is stored as plain ASCII text with no encoding, encryption, or steganography.bashwget <challenge_url>/nothing_up_my_sleevebashcat nothing_up_my_sleeveWhat didn't work first
Tried: Run 'strings nothing_up_my_sleeve' expecting to extract hidden text from a binary.
The file is plain ASCII, so strings produces the same output as cat - but the real trap is assuming the file is binary in the first place. The challenge description says the flag is in-the-clear, meaning cat is sufficient and no extraction tool is needed.
Tried: Open the downloaded file in a hex editor looking for encoded or obfuscated content.
A hex editor shows raw bytes, which for a plain ASCII file just mirrors what cat already displayed. Nothing is encoded or hidden in the byte stream. The title 'nothing up my sleeve' is literal - there is no steganography, encoding, or obfuscation to reverse.
Learn more
The challenge title is a reference to the cryptographic concept of "nothing-up-my-sleeve numbers" - constants chosen in a transparent way to assure users that no hidden backdoors or biases were built in. Here it is used literally: there is genuinely nothing hidden. The flag is sitting in the file as readable text.
wget downloads a file from a URL and saves it to disk. curl -O is an equivalent alternative. After saving, cat prints the file contents to the terminal. These two commands are the entire solution.
This style of challenge is sometimes called a "sanity check" - it verifies that you can connect to the challenge server and run basic command-line tools, rather than testing a specific vulnerability class.
Interactive tools
- Cipher Identifier & Auto-DecoderPaste any ciphertext and the tool auto-runs every common decoder (base64, hex, Morse, ROT, Atbash, Bacon, binary, decimal, URL) and ranks the results by English-likeness.
- Frequency AnalysisAnalyze letter frequencies in a substitution cipher and interactively build the decryption mapping with auto-filled guesses.
Flag
Reveal flag
picoCTF{...}
The flag is stored in plaintext in the downloaded file - no decoding or extra tools required.