All Writeups

Comprehensive collection of CTF challenges, solutions, and insights.

2026-03-01 Crypto Medium

DEADROP Crypto 2 - rsa_briefing.enc

RSA encrypted with e=3 and no padding. The message is small enough that m³ < n, so no modular reduction occurs and the ciphertext is simply the exact cube of the plaintext. Integer cube root recovers it directly.

rsa small-exponent cube-root no-padding

2026-02-28 JWT Medium

WHAMazon! JWT 3 - RSA Revenge

Using provided RSA private key components to manually implement PKCS#1 v1.5 signing and forge a valid RS256 JWT admin token.

jwt rs256 rsa pkcs1-v15

2026-02-23 Crypto Medium

WHAMazon! Crypto 3 - Quarantine Key Dump

Reconstructing n from p and q, diagnosing OAEP padding from garbled raw-RSA output, and decrypting with PyCryptodome's PKCS1_OAEP cipher.

rsa oaep padding pkcs1

2026-02-23 Crypto Easy

WHAMazon! Crypto 2 - You got the key to this room?

Reconstructing a truncated RSA private exponent via brute force over the missing 4 hex digits, then using it to decrypt a raw RSA ciphertext.

rsa partial-key brute-force known-plaintext