MXMedia CipherStream. Preliminary Assessment. Copyright 2012 Farncombe 1.0. Author: T F

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1 MXMedia CipherStream Preliminary Assessment 1.0 Author: T F Copyright 2012 Farncombe Belvedere Basing View Basingstoke RG21 4HG

2 This document and the information contained herein is the subject of copyright and intellectual property rights under international convention. All rights reserved. No part of this document may be produced, stored in a retrieval system or transmitted in any form by any means, electronic, mechanical, or optical, in whole or in part, without the prior written permission of the copyright holder. This report may not be copied or issued in whole or in part without the express permission of MXMedia ( MXMedia ) subject to a confidentiality agreement between all the relevant parties. This report reflects our opinion based on the information available at the time of the review and does not offer any warranty expressed or implied as to the security of the system under review. Document History Version Date Author Comment /11/2012 Tom Thomas Initial Assessment /11/2012 Tom Thomas Updates following review proprietary information. Unauthorised reproduction or disclosure of this information in whole or in part is prohibited. 2

3 Table of Contents 1. Executive Summary System Features Threats Side channel analysis Player attack Recommendations... 7 About Farncombe Consulting Group... 8 proprietary information. Unauthorised reproduction or disclosure of this information in whole or in part is prohibited. 3

4 1. Executive Summary This preliminary review of the MXMedia CipherStream system has been carried out as a paper exercise based on responses to farncombe Minimum Security Requirements questionnaire and other ancillary information provided by MXMedia. This is no substitute for a full review of a system but is a preliminary stage that avoids moving to a full review when easily identifiable problems can be found. In this case the design is still at the stage of detailed architectural design, so we have provided guidelines that will allow the design to be completed in compliance with the minimum security requirements we have provided. MXMedia are designing a bespoke hardware device that implements a secure DRM client. The device is a USB connected stick, that is designed to have an asset uploaded to it via a kiosk and stored persistently within. Bulk storage of content material can be via memory card plugged into the device or connected PC or server HDD. Decrypted content can be rendered on WiFi n HDMI connected devices (that support the appropriate link protection mechanisms). Farncombe have reviewed the initial architectural information provided by MXMedia and find the architecture to be sound, however this is caveated by the fact that the project is still pre production, and many of farncombe s recommendations are focused on the specifics of the bespoke ASIC, which is yet to reach the final design and production stage. We can only say now that if the implementation adheres to the principles outlined in the information submitted to us and follows our recommendations, then the system would be fit for distribution for premium HD content. proprietary information. Unauthorised reproduction or disclosure of this information in whole or in part is prohibited. 4

5 2. System Features MXMedia are implementing several mechanisms in their system that farncombe would regard as sound practice. These include: Asymmetric cryptography for content license encryption, signing and acquisition using RSA 2048 Symmetric cryptography for asset encryption using AES 128 Option to encrypt each asset uniquely to each user Asymmetric signing of device firmware Option to use on board LW time signal clock reference for time bound license check Option to use bespoke WBC based mobile re encryption method, else industry standard DTCP IP or HDMI with HDCP Use of unique monolithic ASIC containing unique secrets, where security is enhanced through diversity from standard off the shelf silicon Strict one way design of decryption datapath within the device ASIC Control/ownership of content path on the device through to baseband proprietary information. Unauthorised reproduction or disclosure of this information in whole or in part is prohibited. 5

6 3. Threats Although delivery of content is direct one to one (as compared with a traditional broadcast TV system for example), the system is based around persistent offline storage of content rather than a strictly streamed model. This provides the obvious opportunity for encryption protected assets and licenses to be easily passed around freely. Many systems relinquish the final decode process to a trusted party, however MXMedia s approach owns the content path through to baseband, thereby protecting the valuable compressed content by design. This means that the robustness of the system relies on: The security of the license decryption process The trust in the player instance 3.1 Side channel analysis The custom architecture of the MXMedia ASIC contains a one way content delivery pipeline serviced by two separate processors with custom instructions extensions, dedicated hardware accelerators and containing hardware cryptography operators. The design will be implemented in a sea of gates, so as to provide additional obfuscation of functional elements. The ASIC presents a no more palatable target for power, glitch and EM analysis, than any other complex SoC might. The cryptographic functions executed are analogous to those executed in a PayTV smartcard in some respects, which is a field where advanced anti snooping mechanisms are employed, such as circuit camouflage, bus scrambling, environmental sensing and hardened cryptographic elementals. 3.2 Player attack Given that the license decryption process uses strong industry standard methods, it is unlikely that an attacker would make this area their first target. The media player/rendering instance is where decrypted decompressed content will be available (transient in memory buffers for example), so care should be taken to secure these buffers from third party attack or subversion. Whilst an HDTV would be an unlikely target for this type of attack, a mobile platform would be more attractive, due to the open nature of contemporary devices. However, here the MXMedia system intends to deploy White Box cryptography rendering code, each time dynamically generated by the player device, with one time keys, the resulting one time mobility of a narrow transient memory buffer and as close as possible direct driving of final content delivery devices. proprietary information. Unauthorised reproduction or disclosure of this information in whole or in part is prohibited. 6

7 4. Recommendations Although on initial inspection we would regard the architecture as essentially sound, there are a number of, as yet, unknown areas where we would make recommendations at this stage: Where applicable, side channel attack hardened implementations of software cryptographic functions; obfuscation of cryptographic intermediaries. These features are finding their way into PayTV SoCs now, so we would expect to see them here. Where applicable, sensible silicon design and layout to mitigate against trivial reverse engineering (e.g. physical spreading and obfuscation of private key bits, bus tracking, metallisation layering, use of circuit camouflage, etc.). These features are finding their way into PayTV SoCs now, so we would expect to see them here. Where applicable, introduction of random noise elements to hardware and software functions in order to mitigate against power analysis. Sound design of device software signature verification mechanism to mitigate against subversion (by attempting to cause hash overflow for example). Hardware random number generator (at least FIPS certified) used to generate symmetric key for WiFi reencryption step. It is recommended that the device software image be encrypted, although this may be mitigated by the verification of manufacturer signature, prior to any execution. Independent penetration testing of the device (white box recommended); including software, protocol and environmental attacks. Secure memory implementation (it is understood that exclusively on chip registers and localised memory is used for transient key material and content). HSM based generation of private key material for chip personalisation. In the full review we would expect to see how these recommendations have been met and how the detail of the design meets the system requirements identified in section 2. proprietary information. Unauthorised reproduction or disclosure of this information in whole or in part is prohibited. 7

8 About Farncombe Consulting Group The Farncombe Consulting Group is a specialised professional services firm operating in the broad digital video technology, telecoms and digital media sectors. Initially focused on pay TV and digital TV technology through founder company Farncombe Technology, it has since grown into a globally recognized television consultancy, servicing a large international client roster that includes broadcasters, operators, telcos, hardware and software suppliers and a variety of government, regulatory bodies and private equity companies. The Farncombe Consulting Group s current focus is on the increased opportunities made available by a converging market which extends from cable, satellite and terrestrial delivery to telco managed IPTV, video over Internet and mobile TV offerings. The Group comprises a number of separate practices covering a wide range of core competencies. These include: Strategy Technology Consulting Programme Management Content Security System Integration Engineering Services Test and Certification Design Practice We apply these competencies to the planning, management, transport and secure delivery of video and other new content services. Farncombe Consulting Group is a private company incorporated in the UK. 100% of our shares are owned by the management team. We are not linked to any technology vendor or service provider, enabling us always to give an honest opinion and take independent decisions solely based on our fair analysis of the situation and our clients' best interests. At Farncombe, we put our customers first; our independence and our impressive track record demonstrate our ability to work over time with any players inside a given industry. Should you require our assistance, please contact us. proprietary information. Unauthorised reproduction or disclosure of this information in whole or in part is prohibited. 8