Avaimenvaihto

Avaimenvaihto is a Finnish term that literally means "key exchange" and can refer to two general concepts in security. In information security, avaimenvaihto describes the process by which two or more parties establish a shared cryptographic key for secure communication. In physical security, it describes changing or replacing mechanical keys or cores in locks to prevent access by former key holders.

In cryptography, key exchange protocols enable two parties to agree on a common key over an insecure channel. Classic approaches include Diffie–Hellman and its elliptic-curve variants, sometimes combined with authentication methods such as digital signatures. A successful avaimenvaihto is typically designed to provide properties such as forward secrecy (past communications remain secure if the server is compromised later) and authentication (verifying the participants). The resulting key can then be used for symmetric encryption of subsequent messages.

In physical security, avaimenvaihto refers to rekeying or replacing locks so that old keys no longer work. This is common when tenants move out, staff changes, or security policies require updated access control. Rekeying usually involves altering the lock cylinders, or replacing them, and issuing new keys to approved individuals. Some systems use master keys or key cards; the principle remains to restrict access by distributing new keys and collecting old ones.

Considerations in both domains include cost, downtime, key management, and the risk of keys being compromised during transfer. In cryptography, proper implementation and up-to-date protocols are essential; in physical security, licensed locksmiths and proper documentation minimize security gaps.

See also: public-key cryptography, Diffie-Hellman, rekeying, lock cylinder.