Abstract: A computer-implemented system for associating digital media files with external commodities wherein a digital media file such as digital art is provided. An external commodity that is unique and has a unique identifier is provided, such as a carbon credit. Ownership of the external commodity is transferred to a buyer when the digital media file is acquired by the buyer. The digital media file is associated with the external commodity by generating a digital signature using a private key from data that includes a hash of the digital media file and the unique commodity identifier. A new, unique digital file is created containing the digital signature as metadata.