You're right! That's perfectly normal and extremely common. People are skittish about this in the realm of cryptography because the costs of getting it wrong c

You're right! That's perfectly normal and extremely common. People are skittish about this in the realm of cryptography because the costs of getting it wrong can be very high. Further, programmers have a culture where experimenting by writing something yourself is perfectly reasonable and extremely common. When these two meet in the context of crypto, I know just enough to get worried that someone's going to get overconfident from a primer and do something they believe to be very clever. History has a nasty tendency to validate fear this as well-intentioned clever people do things that they believe are good enough.