Cisco Systems Cisco Systems Verizon Labs TNO Limelight Networks This document describes how the concept of URI signing supports the content access control requirements of CDNI and proposes a URI signing scheme. The proposed URI signing method specifies the information needed to be included in the URI and the algorithm used to authorize and to validate access requests for the content referenced by the URI. Some of the information may be accessed by the CDN via configuration or CDNI metadata.