• https://cryptohack.org/challenges/
• https://cr.yp.toc.tf/
• http://ctf.usv.ro/
• https://rough.ro/
• https://hackout.ro/
• http://captf.com/practice-ctf/
• https://overthewire.org/wargames/
• https://www.cybersecuritychallenge.ro/
• https://europeancybersecuritychallenge.eu/
• International Olympiad in Cryptography: https://nsucrypto.nsu.ru/
• https://unbreakable.ro/

FULL Cryptography challenges:

• https://cryptohack.org/challenges/
• https://cr.yp.toc.tf/