City of Shadows CTF Challenge - Project Story

What Inspired Me

I love cybersecurity and cryptography. When I saw this CTF challenge, I wanted to test my skills in finding hidden information and breaking different types of encoding. The story about a detective finding evidence against a mafia boss was really cool.

How I Built It

I used PowerShell to write scripts that:

• Searched through all files and folders recursively
• Decoded Base64 and hexadecimal strings
• Analyzed PNG files for hidden text
• Tried multiple character encodings (UTF8, ASCII, Unicode)

My search strategy was systematic:

1. Direct text search for "FLAG"
2. Hexadecimal pattern matching
3. Base64 decoding
4. Multiple encoding attempts
5. PNG file analysis

What I Found

I successfully found 9 out of 9 flags : -FLAG_01{Bank ledger of Rocky's offshore transfers (ID: 45021, 2024-11-03, Unknown Islands)} -FLAG_02{Decrypted chat logs of hits/payoffs (ID: 7812, 2023-05-12–2024-08-21, Encrypted servers)} -FLAG_03{CCTV of henchman at murder scene (ID: 23112, 2024-02-19, Rivertown alley)} -FLAG_04FLAG_final_preview{Steganography_Master_Made_Flag_ID_3421}FLAG_05{Cash bribe -photo with serial numbers (ID: 9921, 2024-06-11, City Hall)} -FLAG_06{Signed memo authorizing illegal acts (ID: 11045, 2023-11-29, Corporate office)} -FLAG_07{Testimony of repentant lieutenant (ID: 5542, 2024-08-02, Witness Protection)} -FLAG_08{Fake contracts & audit trail of embezzlement (ID: 7733, 2022-01-15–2024-07-20, Accounting servers)} -FLAG_09{Social media logs & account evidence (ID: 2323, 2024-09-14, Blockchain ledger)} round2 IDORFLAG{ID0R_1s_s0_e4sy_2025} XSSFLAG{XSS_r3d1r3ct_t0_v1ct0ry} SQLiFLAG{SQL1_byP4ss_w4f_l0l} AdminFLAG{4dm1n_p4n3l_h1dd3n_1n_pl41n_s1ght}

Challenges I Faced

Challenge 1: Too Many Files

• The dataset had 100+ files and 50+ folders
• Solution: Automated search with PowerShell scripts

Challenge 2: Different Encoding Types

• Flags were hidden in Base64, hexadecimal, and inside PNG files
• Solution: Learned different decoding methods and wrote code for each

What I Learned

• Different encoding methods (Base64, hexadecimal, PNG steganography)
• File system analysis and pattern matching

Conclusion

it's about thinking creatively and being systematic.

Thank you for this amazing challenge!

Built With

• ascii
• detection
• file
• forensics
• pattern
• powershell-scripting-hexadecimal-and-base64-decoding-png-file-analysis-md5-hash-analysis-character-encoding-analysis-(utf8
• regex
• steganography
• system
• unicode)