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Writeups

2023 CTF101 8 writeups

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osint

sightseeing-in-ghent

OSINT adventure in Ghent requiring landmark identification, Google Maps investigation, and decoding a hidden sequence from a YouTube video soundtrack.

by Victor Le Pochat 3 min
crypto

Substitution Ciphers

Classic cryptography overview featuring Caesar and Vigenere Ciphers. Demonstrates single-byte XOR bruteforcing and frequency analysis for multi-key XOR decryption.

by r98inver 7 min
crypto

RSA Challenges

Comprehensive walkthrough of three RSA challenges from CTF101, covering basic decryption, factoring using online tools, and exploiting totient multiples from leaked private exponents.

by r98inver 5 min
crypto

Encoding Challenges

Step-by-step guide to reversing complex data encodings. Covers nested Base64/Base16 loops and a custom bit-shifting 'magic shuffle' algorithm.

by r98inver 3 min
osint

sightseeing

OSINT challenge solve involving Leuven landmark recognition, Google Maps review scouting, and a creative hex-to-ASCII video transcription puzzle.

by Victor Le Pochat 3 min
web

poster-thief-3

Hands-on tutorial on manipulating HTTP headers using curl. Demonstrates how to bypass server-side checks for User-Agent, Referer, and custom headers.

by vikvanderlinden 3 min
web

poster-thief-2

Detailed exploration of Path Traversal vulnerabilities. Explains how to bypass non-recursive traversal filters by nesting sequences to reach sensitive system files.

by vikvanderlinden 5 min
web

poster-thief-1

Introduction to the security.txt standard (RFC 9116). Shows how to locate and use a site's security policy to find hidden contact information and flags.

by vikvanderlinden 1 min