Challenges

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Crypto Easy

Ancient Secrets (ROT13)

A ciphertext encrypted with the classic ROT13 (Caesar cipher with shift 13). Decode to reveal the flag.

100 pts
5 solves 🩸
Crypto Easy

Classic Caesar Cipher

A secret message was encrypted using a Caesar cipher with an unknown shift. Can you decrypt it and find the flag? Encrypted message: nFRP{p43f4e_p1cu3e_3m_oe34x}

50 pts
13 solves 🩸
Crypto Easy

Small RSA Exponent Attack

RSA was used with a very small public exponent (e=3). The ciphertext is small enough that m^3 < n, so you can just take the cube root without needing the key!

100 pts
10 solves 🩸
Crypto Medium

XOR Secrets

A repeating-key XOR cipher. The key is 4 characters and a common hacker word. Use known-plaintext attack.

250 pts
4 solves 🩸
Crypto Hard

Tiny RSA

RSA with small 32-bit primes. Factor n to recover d, then decrypt the ciphertext.

400 pts
Crypto Insane

ECC Discrete Log

Elliptic curve discrete logarithm on a weak curve. The curve has small subgroup order, enabling Pohlig-Hellman attack.

500 pts
3 solves 🩸
Crypto Insane

Padding Oracle

AES-CBC padding oracle attack. The server reveals whether decryption has valid PKCS7 padding. Use this oracle to decrypt the flag byte-by-byte.

500 pts
4 solves 🩸