Hierarchical key management system for digital rights management and associated methods

A distributed key management system, comprising:

• a master server operable with a master key material repository for receiving key material from a vendor key management server, wherein the master key material repository is divided into at least a first vendor cache to receive vendor keys from a first vendor and a second vendor cache to receive other vendor keys from a second vendor;
• one or more local servers operable with local key material repositories to deliver both the vendor keys and the other vendor keys with content from the first vendor and the second vendor, respectively, to one or more subscriber devices;
• a plurality of intermediate servers, each operable with an intermediate key repository organized with a hash table;
• and
• a management system, the management system to pre-populate one or more intermediate key repositories with one or more digital rights management keys selected from the first vendor cache and the second vendor cache corresponding to fragments of content prior to the fragments of content being requested by a subscriber device;
• the content comprising video on demand content, the hash table configured as an array of buckets, where each element in a bucket list identifies unique key material having associated therewith a retention priority value indicating a retention priority guarding against automatic removal of the unique key material from the bucket.