ID NAME QUALITY USERS ACC % DIFFICULTY C I
288 Prime or Not   61 3919
22
21
18139 Substitution cipher   3 467
1
4

#cryptography

Cryptography is the science of secret writing, especially code and cipher systems

https://en.wikipedia.org/wiki/Cryptography https://www.khanacademy.org/computing/computer-science/cryptography https://www.coursera.org/course/crypto https://en.wikibooks.org/wiki/Cryptography http://www.garykessler.net/library/crypto.html