Kerckhoffs's principle

Kerckhoffs's principle holds that a cryptosystem should remain secure even if everything about it except the key is public knowledge, a view widely embraced by cryptographers. Dutch cryptographer Auguste Kerckhoffs stated it in the 19th century, in an 1883 article, "La cryptographie militaire," published in two parts in the Journal of Military Science. Claude Shannon later phrased it as "the enemy knows the system," a form known as Shannon's maxim. The article adds that every secret creates a potential failure point, as Bruce Schneier puts it, and that secrets should be those least costly to change if disclosed.