Cloakware Corporation, 260 Hearst Way, Suite 311, Kanata, Ontario, Canada K2L 3H1 Spencer Cheng Trusting DRM Software Presentation to W3C Workshop on DRM January 22-23, 2001 Sophia-Antipolis, France

Cloakware Corporation2 Outline The DRM security model Cryptography’s role The need for trusted agents Hardware Solutions Trusted Software Agents Tamper-resistant software Summary

Cloakware Corporation3 DRM Security Model Trusting the Untrustworthy Past and present R&D focused on hostile S/W u Anti-virus S/W & Java sandbox protects users against dangerous S/W and hostile hosts u Trust only occurs with S/W from well known sources DRM users are assumed to be hostile u All you need is one untrusted user/attacker n Attacker have legitimate access to protected content n Attacker have infinite time and resources n Attacker has complete access to S/W and H/W

Cloakware Corporation4 Cryptography is part of the solution Store/stream data in encrypted form to prevent direct access Use a “key” to access content u Where do you store the key? u What if Alice can’t trust Bob with the key? u Who/what checks the integrity checker? u How do you protect the executable? DeCSS and Steven King’s ebook crack were made possible by cryptographic solutions implemented in unprotected software Tamper-resistant S/W complements cryptography in hostile environment n Provides a “Trusted Agent” on client/player to protect decryption key and enforce access control

Cloakware Corporation5 Hardware Solutions Hardware solutions are used for key hiding & tamper resistance Hardware has several drawbacks u Incompatible with installed base of PCs, players u Time and expense to build installed base u Long lifecycle means devices must remain secure for years u Field Upgrades – difficult & costly to replace hardware when it is compromised

Cloakware Corporation6 Trusted Software Agents Reduced manufacturing and distribution costs Compatible with installed base Faster time-to-market Renewable and flexible u Attacks continue to improve/evolve u Replaceable tamper resistant components are essential Easy to manufacture unique agents u Prevents a single crack from compromising a DRM system The Chain of Trust u Content providers may want trusted components on distributors’ servers u Distributors may want trusted components on commerce service providers servers

Cloakware Corporation7 Tamper Resistant Software Tamper resistant libraries & current code obfuscators are inadequate u Offer weak obfuscation and little protection against tampering Portability is key for trusted software agents u Heterogeneous environments are here to stay u Binary-based tamper-resistant software solutions are not portable u Source level tamper resistant solutions are desirable to support multiple platforms and O/S’s

Cloakware Corporation8 Summary DRM Trust model very different u Broad distribution means some users will be malicious Cryptography is part of the solution Trusted Software Agents are required fo u Key hiding u Protecting the rights enforcement engine against tampering u Should be renewable and flexible Cloakware’s TRS technology u Portable source level technology u Protects against tampering and reverse engineering u Enables the manufacture of unique trusted software agents