Data Protection and Security

I

Introduction To Cryptography

I.I

Cryptography and Its Applications

History of Cryptography

Cryptography has a fascinating history and dates as far back to 4000 years ago. The earliest example of an attempt to obscure the meaning of an inscription was found in Egypt. The first notable personality in the history of cryptography is probably Julius Caesar (100 – 44 BC), who used the “Substitution Cipher” for government communication. In these early days, encryption was mainly performed using “pen and paper”, therefore the methods were ad hoc, simple and inefficient. Only in 1900’s, the invention of mechanical devices called “rotors” allowed more sophisticated and systematic techniques for cryptography.

As written by Whitfield Diffie in the foreword of the book “Applied Cryptography” (written by Bruce Schneier), until the First World War, important developments did not appear timely and the science of cryptography moved forward in the same way as most other specialized disciplines. Starting in 1918, the milestones of cryptography are as follows (detailed introduction of earlier history can be found in David Kahn’s book.):

1918: William F. Friedman’s monograph “The Index of Coincidence and Its Applications in Cryptography” appeared as a research report.

1918: Edward H. Hebern filed the first patent for a rotor machine.

1933: The Enigma machine, used by Germany in WW2, was broken by Marian Rejewski.

1949: Claude Shannon’s paper “The Communication Theory of Secrecy Systems” appeared in the Bell Systems technical journal.

1967: David Kahn’s book on the history of cryptography, “Codebreakers” was published.

1970: At IBM, Horst Feistel began the development of what was to become the U.S. DES (Data Encryption Standard).

1976: Whitfield Diffie and Martin Hellman published “New Directions in Cryptography”, introducing the idea of public key cryptography.

1978: The first realization of public key cryptography, RSA algorithm was published in Communications of ACM.

1991: Phil Zimmermann releases the public key encryption program PGP along with its source code, which quickly appears on the Internet. Zimmermann spent years under investigation because of his release of PGP.

2001: After a competition, Rjindael algorithm was chosen as AES (Advanced Encryption Standard).

2005: SHA-1, one of FIPS (Federal Information Processing Standards) approved hash functions, was broken.