Consider this: the German Enigma cipher algorithm
was, for its day, essentially impregnable; yet the Poles cracked it using pencil-and-paper by exploiting weaknesses of the German keying
system. The choice of algorithm matters relatively little, esp. for civilian-grade crypto. How the algorithm is applied, though, matters much.
Use an existing
crypto system of known provenance, and learn how to use it correctly and strongly. Good examples include:
- GnuGPG / PGP
- The OpenSSL crypto library
These technologies are used all over the world. They are well-understood, professionally designed, and well maintained. They are also shared
by people with whom you will wish to communicate, most of whom you may never have met and will never meet.
There are well-understood best practices,
and these are the most vital aspect of ensuring that your information is both secure, trustworthy, and intact.