Kerckhoffs was born in Nuth, the Netherlands, and was baptised as Jean-Guillaume-Hubert-Victor-François-Alexandre-Auguste Kerckhoffs von Niuewenhof, although he later shortened his name. Kerckhoffs studied at the University of Liège. After a period of teaching in schools in the Netherlands and France, he became a professor of German at the Parisian Ecole des Hautes Etudes Commerciales and Ecole Arago.
He is best known today for a series of two essays he published in 1883 in le Journal des Sciences Militaires ("Journal of Military Science") entitled La Cryptographie Militaire ("Military Cryptography"). These articles surveyed the then state-of-the-art in military cryptography, and made a plea for considerable improvements in French practice. They also included many pieces of practical advice and rules of thumb, including six principles of practical cipher design:
- The system should be, if not theoretically unbreakable, unbreakable in practice.
- Compromise of the system should not inconvenience the correspondents.
- The key should be rememberable without notes and should be easily changeable
- The cryptograms should be transmittable by telegraph
- The apparatus or documents should be portable and operable by a single person
- The system should be easy, neither requiring knowledge of a long list of rules nor involving mental strain
The most well-known is the second of his six principles, also known as Kerckhoffs' law. It can also be understood as the idea that the security of a cryptosystem must depend only on the key", and not on the secrecy of any other part of the system.
In 1885, Dr. Kerckhoffs became interested in the constructed language Volapük, and for several years was a leading member of the Volapük movement, and Director of the Academy of Volapük. He published several books on the subject and introduced the movement to France, Spain and Scandinavia through a series of public lectures.
- La Cryptographie Militaire — French original and translations into English