1. A method of accessing content according to a DRM policy using a device, comprising: operating, by the device, a DRM engine and a cryptographic services module; receiving, by the device, an encrypted content item, a first link object signed by a link object key, and a certificate comprising a constraint program for validating the link object key, wherein the first link object references a first object and a second object ; authorizing, by the device, access to the encrypted content item using the DRM engine and the cryptographic services module, authorization comprising: determining an authorization of the link object key to sign the first link object using the DRM engine by executing the constraint program using at least one of first attributes of the first object and second attributes of the second object, and based on the execution of the constraint program, determining satisfaction of usage conditions for the link object key; based on the determined authorization of the link object key to sign the first link object, verifying the certificate using the cryptographic services module; based on the verification of the certificate, constructing an authorization graph by processing two or more link objects including the first link object using the DRM engine; querying the authorization graph using the DRM engine; and based on a result of querying the authorization graph, authorizing access to the encrypted content item using the DRM engine; and based on the access authorization, decrypting, by the device, the encrypted content item and accessing, by the device, the content item.