Flag in Flame

Easy
Time Spent: 10 minutes
https://play.picoctf.org/practice/challenge/523

🧠 What I Practiced/Learned/Discovered

  • Discovered tesseract which is a tool that helps extracting text on an image.
  • How to easily decode encoded strings and identify encoding algorithm applied to a text.

🔧 Tools used

Websites

Linux shell

  • base64 (decoding)
  • cat
  • tesseract (OCR)

Steps

  1. The file looked like a base64 code so I tried cat logs.txt | base64 -d but it returned me weird characters Image

  2. Those characters reminded me of when I open images as text, so I tried to give the output to an image file instead cat logs.txt | base64 -d > output.jpg and it gave me a picture

  3. Opened the picture and saw a text in the middle of the picture. The text was so long I couldn’t retype it and I couldn’t also directly copy the text using my mouse.

  4. Searched for a text-on-image extractor and found a tool called tesseract

  5. Installed the tool : sudo apt install tesseract-ocr

  6. Run the command : tesseract output.jpg result

  7. Got the text and copied it

  8. Went on dcode to try to find the encoding algorithm : https://www.dcode.fr/identification-chiffrement

  9. It gave a really positive result on ASCII Image

  10. So I tried to decode it in ASCII and got the flag : https://www.dcode.fr/code-ascii