TSIG – TSIG (Transaction SIGnature) is a computer-networking protocol defined in RFC 2845. Primarily it enables the Domain Name System (DNS) to authenticate updates to a DNS database. It was most commonly used to update Dynamic DNS or a secondary/slave DNS server. TSIG uses shared secret keys and one-way hashing to provide a cryptographically secure means of authenticating each endpoint of a connection as being allowed to make or respond to a DNS update.