Messages have been encrypted for millennia. Successfully hiding the plaintext has required increasingly sophisticated algorithms to defeat advances in crypto-analysis.
Claude Shannon proved information theoretic security of the Vernam scheme, a.k.a. one-time pad. Since a one-time pad must be as long as the plaintext and can only be used once, the method is not widely used.
Complexity theoretic security provides less strong but more practical security guarantees.
Encryption provides confidentiality. In order to also ensure data authenticity, additional techniques are needed, such as Message Authentication Codes (MAC) or hashing. Alternatively, authenticated encryption combines confidentiality and data authenticity.
Users of symmetric cryptography need to share a key between communicating parties. This is hard to do securely. Public key cryptology addresses this key distribution problem. Moreover, it affords digital signatures.
In practice, public key cryptography is too slow to encrypt large amounts of data. Hence it is used for key agreement.
A lecture by Bart Preneel at SecAppDev 2015 in Leuven, Belgium.
Professor Bart Preneel of KU Leuven heads the COSIC (COmputer Security and Industrial Cryptography) research group. His main research area is information security with a focus on cryptographic algorithms and protocols as well as their applications to both computer and network security, and mobile communications.
He teaches cryptology, network security and coding theory at the K.U.Leuven and was visiting professor at the Ruhr Universitaet Bochum (Germany), the T.U.Graz (Austria), the University of Bergen (Norway), and the Universiteit Gent (Belgium). In '93-'94 he was a research fellow at the University of California at Berkeley. He has taught intensive courses around the world.
He undertakes industrial consulting (Mastercard International, S.W.I.F.T., Proton World International,...), and participates in the work of ISO/IEC JTC1/SC27/WG2.
Professor Preneel is Vice President of the International Association for Cryptologic Research (IACR) and co-founder and chairman of LSEC vzw (Leuven Security Excellence Consortium).