Patent ID: 8255684

Claim:
A method for authentication of a plurality of sites in a land mobile radio (LMR) system and for encryption of messages exchanged by the sites, the plurality of sites being connected by a data network, comprising: transmitting by a first site its certificate, wherein the certificate is created by a trusted authority by encrypting the public key, the ID and other relevant information of the first site with the trusted authority's private key; receiving, by the other sites in the LMR system, the certificate transmitted by the first site; decrypting, by the other sites, the certificate transmitted by the first site and authenticating the first site, wherein the certificate is decrypted using the trusted authority's public key; generating a session key that is a shared session key that is valid across a multicast group of which the sites in the LMR system are members; encrypting the session key with the public key of the first site and transmitting the encrypted session key to the first site; decrypting, by the first site, the encrypted session key with the first site's private key; and multicasting to the multicast group, by the first site, a message encrypted with the session key.