Well, I would like to use DES or BASE64 which are symmetric, i.e. encryption of a plain text produces a cypher text, and description of the cypher text produce the original plain text.
However, only by reading its MAN page, it turned out to be very very very difficult to understand and use it.
Even at the OpenSSL web site, there was no good tutorial on how to use it.
I wasted almost a whole day to figure out how to use it, and fortunately I think I found it.
Well, if you download the source codes, there is a directory for testing, “test”. And there is a destest.c.