I was bored this weekend, scrolling through feeds in twitter and found out that google’s CTF for beginners is open. So I decided to give it a try. I have attended some CTFs before but haven’t completed any challenges. Those were not beginner friendly. I was able to complete only three challenges in this CTF.
LETTER:
The file `5a0fad5699f75dee39434cc26587411b948e0574a545ef4157e5bf4700e9d62a.txt` was downloaded when I clicked the Attachment link.
When I opened it I noticed it was not a valid text file. So i guessed it would be a zip file and changed the extension and extracted the contents. there was a pdf file inside. with password hidden.
I just selected the password and it revealed. It was that easy.
OCR IS COOL:
I downloaded the attachment and again changed it to zip and extracted there was this OCR_is_cool.png file. It was a screenshot of an email with gibberish words. I spent some time to figure out what it could be. Then it strike my mind after taking a deeper look at the first word. I found out that the first word used was substitution for ‘Dear’ then I realized it is a Caesar cipher with key 19. I didn’t notice that the hint ‘Caesar’ given in the challenge description until I have found the flag.
Read the challenge description properly before proceeding to get the flag.
For those who aren’t familiar with Caesar cipher. It is a simple encryption method to convert plaintext to ciphertext. For more info watch this video
I uploaded the image to this website and got the text and i decrypted the ciphertext with key 19 with this online Caesar decryption tool and got this.
the flag was CTF{caesarcipherisasubstitutioncipher}.
FLOPPY:
I downloaded and extracted the attachment and found a foo.ico file.
There was no information to get from this ico file. I fired up the hexeditor to find out if there was any file hidden in it.
You can find the letters PK and driver.txt. PK means that there is a .zip file embedded in it.
I extracted the contents using foremost. you can also use binwalk to extract the embedded files.
and the driver.txt file had the flag CTF{qeY80sU6Ktko8BJW}.
I was able to complete only three challenges.
This is my first post. Thank you for reading till the end.
