This document is one of a series of documents that specify the IPTV Security Solution (ISS). This document specifies the IPTV Security Solution/Authentication (ISS/A), which is used to authenticate downloads and messages to IPTV receiving devices. For further information, please refer to companion documents IPTV Security Solution/Certificate (ISS/C) and IPTV Security Solution/Root (ISS/R). In the future, this document is expected to include the IPTV Security Solution/Encryption (ISS/E), which would be used to encrypt downloads and messages.