1.3.2 Digital Rights Management Version 7

Digital Rights Management Version 7 provides the means of acquiring a license for Windows Media content. Its packets include a client request for a license and a server response that contains the license.

Figure 2: DRM version 7 license request and response

The Digital Rights Management client generates a license request and sends it to a license server. The request is in extensible markup language (XML) format, partially RC4-encrypted, and then encoded using the base64 algorithm, as specified in section 2.2.1.1. It is sent to the server by means of an HTTP POST request. For more information about RC4, see Remarks at the end of this topic.

The response is an RC4-encrypted XML packet. The first 80 bytes of the license response packet are an ECC-encrypted RC4 key. The RC4 key is generated by the server using the EncRandNum member of the CLIENTID structure, section 2.2.3.1.3.4, sent by the client within the license request. The remainder of the packet (the license data itself) is encrypted with the generated RC4 key. The packet is then encoded with the base64 algorithm, as specified in section 2.2.1.1. It can contain any number and combination of version 1 and version 7 licenses. Each version 7 license is itself RC4-encrypted using the mechanism described in this topic.

A WMDRM: License Protocol version 7 license is represented, as specified in section 2.2.3.2.4.2.

The structures that are used by both version 1 and version 7 of the WMDRM: License Protocol are specified in section 2.2.1.

This protocol uses the following packets.

Packet	Description
DRM Version 7 License Request	Contains the client's request for a license.
DRM Version 7 License Response	Contains the server's response to the client's request for a license.
DRM Version 7 License Format	Contains an XML-formatted license.

RC4 is a proprietary encryption algorithm available under license from RSA Security, as specified in [RSAFAQ].