This book explains compactly, without theoretical superstructure and
with as little mathematical formalism as possible, the essential
concepts in the encryption of messages and data worthy of protection.
The focus is on the description of the historically and practically
important cipher, signature and authentication methods. Both symmetric
encryption and public-key ciphers are discussed. In each case, the
strategies used to attack and attempt to "crack" encryption are also
discussed. Special emphasis is placed on the practical use of ciphers,
especially in the everyday environment. The book is suitable for working
groups at STEM schools and STEM teacher training, for introductory
courses at universities as well as for interested students and adults.