A Digital Rights Enabled Graphics Processing System

1
A Digital Rights Enabled Graphics Processing
System

• Weidong Shi
• Hsien-Hsin Sean Lee
• Richard M. Yoo
• Alexandra Boldyreva

Motorola Labs Georgia Tech Georgia Tech Georgia
Tech
2
Why Digital Rights Management (DRM) and Content
Protection?

• id software Kevin Cloud
• "this (piracy) is whats killing
• PC games"
• but you may literally have more games being
  played illegitimately than being played
  legitimately.
• it is a very serious problem. 
• There isnt any magical solution, or else wed
  solve it.

3
Graphics As Assets

• Protect graphics apps by protecting the graphics
  assets instead of the sw.
• Avatars, in-game graphics assets sale raise
  steadily
• 10M per month in-game assets sale in Korea alone
• 880M trading in US (2004)

4
It is a non-trivial task

• If security is easy to add, it is easy to remove.
  
• Never underestimate the hackers (XBOX incidence)
• Graphics DRM
• Protect against SW attacks
• Protect against simple
• Radioshack HW attacks

5
Software-based DRM

• Disadvantages
• Insecure
• Not tamper proof
• Advantages
• Easy to change
• Flexible

3D apps
mesh
texture
shader
OpenGL/ Direct3D
DRM
SW
Frame Buffer
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DRM Design Space
DRMed Contents

• Many design choices for unlocking DRMed contents.
  
• Hackers can always go to the level below to
  defeat a DRM system.
• Typical SW DRM unlocks at App level.

Unlock at App level
Real time 3D apps
Graphics API(OpenGL/Direct3D)
Unlock at API level
Device Driver
Unlock at Driver level
Unlock at Device level
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Our Idea DRM Enabled GPU
DRM
DRM Enabled GPU

• Protect graphics assets with encryption and
  rights licenses.
• Decrypt graphics assets by a DRM enabled GPU

Protected Graphics Assets (mesh, textures,
shaders)
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DRM Enabled GPU

• Advantages
• Strong security protection, contents decrypted
• right before their consumption
• Against SW tampers/attacks
• API hijack, graphics file reverse engineering,
  etc.
• High performance
• HW decryption vs. SW decryption
• Disadvantages
• Less flexible

9
GPU with DRM Block
Graphics/Video Memory
PCI-Express
Host/Memory Interface
DRM Block
Context Information
Vertex Cache
Texture Cache
Cryptographic Unit
License Processing Unit
GPU Pipeline
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Rights License and Content Keys

• Graphics contents or assets are licensed
• Graphics contents or assets are encrypted with
  content keys. Encrypted content keys included in
  graphics content licenses.
• Content licenses are certified and distributed
• Only targeted GPU can extract/use the content
  keys from the licenses.

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Binding Context
Binding Context
Vertex Attr Decryption Key, Digest Key
Texture Decryption Key, Digest Key
Shader Digest Key

• Constraints of binding among vertex data,
  textures, and shaders
• Created based on graphics assets licenses
• Security context (protected when stored in
  exposed storage)
• Contains all information for decrypting graphics
  assets by a GPU

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Graphics API Extension

• Encrypted Data Array/Texture Types
• Encrypted234f, Encrypted_R8G8B8A8,
• Encrypt collection of vertex attributes or
  texture tile as a chunk.
• Compute a digest or hashed MAC for each encrypted
  chunk
• Protected Graphics Objects
• glVertexAttribPointerPrivateARB(
• 0, Encrypted4f, GL_FALSE, 0, vertex)
• glVertexAttribPointerPrivateARB(
• 8, Encrypted2f, GL_FALSE, 0, text_coord)

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Graphics API Extension

• API Extension
• GenBindingContext(int size, int
  ptr_to_handles)
• ConfigBindingContext(
  
  int handle, enum type, int
  graphics_object_handle, unsigned
  char license)
• type Encrypted_VERTEX_ATTR0..15
• type PRIVATE_TEXTURE0..7
• type VERTEX_SHADERFRAGMENT_SHADER
• graphics_object_handle handle
  to vertex,texture,or shader
• license license byte array
• EnableBindingContext(int handle)
• DisableBindingContext(int handle)
• DeleteBindingContext(int handle)

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Graphics Data Protection Check
Encrypted Vertex Attr/Tex Tiles
Encrypted Vertex Attr/Tex Tiles
Digest/ HMAC
Digest/ HMAC


Encrypted Vertex Attr/Tex Tiles
Digest/ HMAC
Binding Context
Vertex/Tex Cache Vertex/Tex Fetch Unit
Decryption Unit
Vertex Attr Decryption Key, Digest Key
Texture Decryption Key, Digest Key
Shader Digest Key
?
HMAC Unit
GPU Front-End
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Counter Mode Example (Encrypted Texels)

Graphics Memory
Graphics Memory
Memory Unit

Fetch Address Cal/Translation
Encrypted Texels
Decryption Pad
AES Engine
Vertex/Tex Cache Vertex/Tex Fetch Unit
XOR
Counter value
Decryption Key
GPU Front-End
Binding Context
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Division of Labor CPU-GPU Level-of-Detail
Collision detection Coarse backface culling
CPU
Transformation Lighting Animation
GPU

• CPU processes unprotected coarse level graphics
  data
• GPU processes protected fine-grained graphics
  data

17
Optional Depth Buffer Protection
Depth Buffer

Z-tile
Z-tile
Context
Depth Decryption Unit
Depth Encryption Unit
Depth Buffer Symmetric Key
Frame Buffer Operation Unit

• Depth buffer key is applied to an application.

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Evaluation
Setting
Apps Quake 3D 4 demo maps
GPU Simulator Qsilver (UVa)
AES unit 8 (400K gates each)
Decryption Throughput/Latency 40Gb/ps x 8, 2.5ns per stage x 11 27.5ns
HMAC Unit 8 (19K gates each)
HMAC Latency 74ns
Graphics Memory GDDR3 latency
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Frame Rate Impact

• Frame rate slowdown using protected assets
  against regular assets
• Reasonable impact on frame rate

20
Decryption Latency Sensitivity
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Sensitivity of Cache Miss Rate
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Conclusions

• Time to introduce DRM protection on real time
  graphics assets.
• The trend of GPU advancement enables new ways of
  protecting graphics assets.
• Graphics assets protection advocates joint
  research from DRM, Graphics, and GPU community.
• GPU-based graphics assets protection is more
  effective.
• We studied feasibility of GPU based graphics DRM.
• Further research is required.

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Thank You!
http//arch.ece.gatech.edu