Cryptopals strikes me as a very good way of scaring people from not only inventing, but also implementing their own crypto.
Now that's very useful.
The real way to learn cryptography is to go through the National Cryptologic School at the National Security Agency in Maryland. They used to start everyone out with paper and pencil cryptanalysis. They classically emphasized that most cyphers are broken because someone made an error in key management. (See Venona). That's probably still the case.
"No new cypher is worth looking at unless it comes from someone who has already broken a very hard one" - Friedman.
Now that's very useful.
The real way to learn cryptography is to go through the National Cryptologic School at the National Security Agency in Maryland. They used to start everyone out with paper and pencil cryptanalysis. They classically emphasized that most cyphers are broken because someone made an error in key management. (See Venona). That's probably still the case.
"No new cypher is worth looking at unless it comes from someone who has already broken a very hard one" - Friedman.