Which principle of cryptography allows algorithms to be publicly disclosed?

Kerkchoff's principle is the foundational idea in cryptography that asserts the security of a cryptographic system should not depend on the secrecy of the algorithm but rather on the secrecy of the key. This principle allows cryptographic algorithms to be publicly disclosed without compromising their security. The rationale behind this is that as long as the key remains secret, even if an attacker knows the algorithm, they cannot decipher the encrypted data.

This principle fundamentally contrasts with older notions of keeping the algorithm secret to protect the system, which has been shown to be less effective. Transparency in the algorithm allows for peer review and scrutiny, helping identify weaknesses and vulnerabilities that can be addressed, ultimately strengthening the security system as a whole.