Kulcscserét

Kulcscserét is a Hungarian term that denotes the exchange or rotation of keys, used in both physical security and cryptography contexts. It is formed from kulcs (key) and csere (exchange) and functions as a general label for processes that establish or update access keys.

In physical security and access management, kulcscserét refers to the reissuance and distribution of physical keys or access credentials. This includes revoking old keys, issuing new ones when personnel change, updating access permissions, and maintaining records of who holds which keys. The practice aims to control entry to buildings or secure areas and to reduce the risk of unauthorized access through key fatigue, loss, or theft.

In cryptography, kulcscserét commonly means a key exchange or key establishment protocol. Here, two or more parties establish a shared cryptographic key over an insecure channel, enabling confidential communication. Key exchange is typically distinguished from key transport: in the former, the parties derive a common key (key agreement), while in the latter, one party generates a key and securely delivers it to the other. Well-known examples include Diffie–Hellman and its elliptic-curve variants (ECDH), as well as RSA-based key exchange methods. Good practices emphasize authentication, forward secrecy, appropriate key lengths, and protection against key compromise.

Historically, the concept of key exchange emerged in modern cryptography in the 1970s, revolutionizing secure communications by enabling secret keys to be established without a prior secure channel. Today, kulcscserét remains central to both physical access policies and digital security architectures.