You are on the wrong path!
there are no COBOL related basics of cryptography
You should learn to distinguish between logic/algorithm and implementation
the cryptography core is the algorithm
the implementation is just a useless detail
Your approach is leading You to the wrong path,
it would be good to read
and lurk thru the content of
here is another sample of what You might find by googling yourself
the first characteristics of a cryptographer is the curiosity, an imaginative mind and a strong mathematical background
asking people to do the research for You is a proof the You do not have the <imprinting> for it and You are just wasting time!
and as all the security experts tell
cryptography, authentications, <security thru tools and devices> are almost <irrelevant> in the implementation of a secure system
there are lots of weaker points ...
You can break a system secured with cryptography, authentications, <tools and devices> with time and the proper skills
but if a system is worth to be broken into it ... much cheaper to do it with MONEY
( systems worth breaking into I said, not just a silly bank robbery )