CryptoHack
A free, fun platform for learning modern cryptography
Learn By Doing
Learn about modern cryptography by solving a series of interactive puzzles and challenges. Get to know the ciphers and protocols that secure the digital world by breaking them.
Level Up
Earn points by solving challenges. Finish categories to earn trophies and gain levels to track your progress. Can you reach the top of the scoreboard?
Fresh Challenges
We are constantly creating new challenges to keep your crypto knowledge up to date. Expect exciting brainteasers and whole new categories as the site continues to grow.
New Challenges
| Origami (NNS CTF 2025) | CTF Archive | 0 |
| Common Ground | Mathematics | 75 |
| Rhetorical Oracle | Symmetric Ciphers | 100 |
| Rhetorical Oracle 2 | Symmetric Ciphers | 150 |
| Long Story Short | Hash Functions | 60 |
Weekly Top Users
| #1 | divyanshu_dt | 5540 |
| #2 | NoBirdWasHam | 4915 |
| #3 | VuiVe | 4825 |
| #4 | surajs2007 | 4635 |
| #5 | Pkv123 | 4620 |
Recent Solves
| No Leaks | LACiA | |
| Moving Problems | Marchet_91 | |
| Great Snakes | rusmi | |
| Finding Flags | Lossy4 | |
| Favourite byte | ajia008 |
Recent Solutions
| Modular Exponentiation | WildanAliAkbar | 0 |
| The j-invariant | dXNlcm5hbWU_ | 0 |
| XOR Properties | MORIS_0101 | 0 |
| Bytes and Big Integers | Beeair19 | 0 |
| Flipping Cookie | OutOfTheWell | 0 |