A flexible framework for generating “scalable layered access” codestreams allows a bitstream architect to select the number of access types and the number of access layers within each access type. At least some of the access layers are encrypted (or scrambled). Some of the access layers may be left unencrypted or unscrambled to allow free access to those layers. The framework facilitates simultaneous access of multimedia content by different users enjoying selective decryption of different access types and different access layers. An exemplary key schema for the framework sends only one or only a few keys to an end user for a given access layer, from which decryption keys for the content can be derived by hashing and then combining under a Group Diffie-Hellman key agreement. In one implementation, only one key is sent in a license to an end user and other partial key information for Group Diffie-Hellman combination with the licensed key is included in the publicly distributed codestream.