Disclosed is a vehicular update system including a communication device configured to communicate between a server and a controller included in a vehicle, a memory, and a controller configured to, (i) when a public key set including a root public key for verifying a root signature is stored in the memory, acquire the root signature from the server and verify root metadata based on the acquired root signature and the root public key of the public key set pre-stored in the memory, and configured to, (ii) when the public key set is not stored in the memory, acquire, from the server, root metadata including a public key set and a root signature obtained by performing a digital signature on a hash value of the public key set using a root private key, verify the root metadata based on the root public key of the acquired root metadata and the root signature, and store the public key set.