Kerckhoff’s Principles

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In 1883, Auguste Kerckhoff, a Dutch cryptograph, outlined six principles for all cryptographic systems.

• second rule is still in play today
  • known as Kerckhoff’s principle

Kerckhoffs’ Principle states that the security of a cryptographic algorithm depends only on the secrecy of the key.

• details of the cryptographic algorithm can be made public
• is applied to all contemporary encryption algorithms

6 Principles

1. The system must be substantially, if not mathematically, undecipherable.
2. The system must not require secrecy; even if stolen by the enemy, the system should remain secure.
3. The keys must be easy to communicate and remember without written notes, and they must be easy to change or modify to use with different participants.
4. The system ought to be compatible with communication via telegraph.
5. The system must be portable, and its use must not require more than one person.
6. Finally, the system must be easy to use, requiring neither complex thinking nor the knowledge of a long series of rules.