IIEST • Instruo 2025

CTF Challenge Writeups

Comprehensive solutions and methodologies for steganography, reverse engineering, cryptography, and web security challenges

14
Challenges Solved
7
Categories Covered
25+
Tools Used
100%
Educational Value

Challenge Writeups

Click on any challenge to view the complete solution

Web

Welcome Everyone

Your first challenge! Find the flag in JavaScript bundle

150 pts Easy
EOF{f0und_m3_f!nally}
General

Sanity Check ⚠️

Mandatory! Find flag in rulebook PDF (disqualification if not solved)

MANDATORY Easy
EOF{h3r3_w3_90_4941n}
Steganography

Hiding in Plain Sight

PDF with hidden text after EOF marker

150 pts Easy
EOF{u_r_@_ch!ck3n}
Crypto

Wrong Number

Audio password, AES-encrypted ZIP, and ROT-20 cipher

150 pts Easy
EOF{4nd4n_w4_d1nw4v4w}
OSINT

A Noob's First Milestone

GitLab profile search and source code analysis

150 pts Easy
EOF{script_kiddie@eofool.com}
Cryptography

Timeless Melodies

Morse code in audio + Vigenère cipher with "Für Elise" key

150 pts Easy
EOF{decrypted_text}
Steganography

Like Finding a Needle in the Hay Stack

Multi-layered steganography with PNG, MP3 extraction, and Caesar cipher

500 pts Hard
EOF{b3war3_!t$_c0m!ng_f0r_u}
Reverse Engineering

Fooled

ELF binary analysis, custom encryption, and base64 decoding

600 pts Hard
EOF{not_a_foolish_person_ig}
Misc

Random Gibberish

Esoteric NGFYU language, base64 URLs, and brightness/contrast steganography

200 pts Medium
EOF{@stley}
Steganography

Recursive Hell

68 nested ZIPs and 48 base64 layers - 116 total iterations!

Expert Expert
EOF{its_a_damn_loop}
Reverse Engineering

Amen

32-bit binary, PRNG-based encryption, and data array extraction

Medium Medium
EOF{wh3r3_ar3_my_po1n+5}
Steganography

Banananana 🍌

Simple string extraction from WAV file

200 pts Medium
EOF{hidden_among_bananananananana}
OSINT

Apples 🍎

Death Note themed: YouTube → Caesar cipher → Google Drive → strings

300 pts Hard
EOF{apples_apples_everywhere_raaaah}
Web

Cannon Ball

Web recon, hidden resources, base64 URIs, and LSB steganography

Medium Medium
EOF{F0und_!t}

Essential CTF Tools

Steganography

binwalk, exiftool, zsteg, steghide, strings

Reverse Engineering

Ghidra, IDA Pro, GDB, objdump, radare2

Web Security

curl, Burp Suite, wget, DevTools

Cryptography

CyberChef, hashcat, john, openssl

Scripting

Python, Bash, Ruby, Node.js

Utilities

file, hexdump, xxd, dd, base64