US Patent 9998477 Digital content access control

Access to a linked resource may be protected using a time-based transformation of links to the resource. A linked resource may be transmitted to a browser in a markup language page. Information indicative of a time-based transformation of a link may be transmitted to the browser in the markup language page, or separately from the markup language page. The time-based transformation may be applied to the transmitted link. The transformed link may be requested, and compared to a version of the link that has been transformed, using the time-based transformation with respect to the time the request is received.