Author
Auguste Kerckhoffs
1 reading card from 1 book · 1883.
1 card
La cryptographie militaire · 1883
Security must survive full publication of the system, except the key.
Kerckhoffs analyzes military cryptography and draws a counterintuitive conclusion: a cipher does not become safer by being kept secret. On the contrary, a system assumed to stay hidden collapses completely the moment it falls into the wrong hands. If, instead, the enemy knows the mechanism and the only variable is the key, security reduces to protecting one small object that can be replaced. A public cipher, tested by many experts, earns trust through repeated failed attempts to break it. His example: an army with thousands of users cannot keep a procedure secret, but it can keep a key. This idea underpins modern cryptography, where algorithms are public and audited, while keys are private and regularly rotated.
“The system must not require secrecy, and it must be able to fall into the hands of the enemy without inconvenience.”