Systems and methods which may be implemented as software to control access to content streams transmitted from a service provider's server. A software solution forces each set top box (STB) to periodically uplink to the server and to receive authentication from that server. To prevent spoofing, the server periodically loads to each STB at least one unique key that is required to access the content stream or that is required for authentication. The key or keys may be periodically revoked and/or replaced by the server. The frequency of the revocation and/or replacement of the key is ideally not fixed. Also, the server may periodically upgrade the decoding and/or authentication software on the STBs via the uplink.