1 / 10

RC5 Encryption Block for wireless Tire Pressure Monitor (wTPM)

RC5 Encryption Block for wireless Tire Pressure Monitor (wTPM). Victor Wen EE241 Project Presentation 05/09/2005. Background. Federal mandate Required for 2008 model year vehicles < 10,000lbs Indirect method inaccurate Use existing ABS sensors Only distinguish relative pressure

marsden-case
Download Presentation

RC5 Encryption Block for wireless Tire Pressure Monitor (wTPM)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. RC5 Encryption Block for wireless Tire Pressure Monitor (wTPM) Victor Wen EE241 Project Presentation 05/09/2005

  2. Background • Federal mandate • Required for 2008 model year vehicles < 10,000lbs • Indirect method inaccurate • Use existing ABS sensors • Only distinguish relative pressure • Direct method • Individual P/T sensor in each tire • data broadcasted wirelessly to onboard computer RF “Hmm..I will alert the driver” “I am flat!”

  3. Motivation/Limitations • Extreme low power requirement • ~4000J for 10 years (typical lithium coin button battery) • RF, sensor and uController consumes power! • 10uW design goal  sub/near threshold voltage? • Why RC5? • Symmetric cipher; low hardware overhead • Authentication needed; only care about my own tires • Encryption of data not needed • Parametrizable (choose w8/r8/k16) • Well-tested

  4. Grand Scheme Sensor uController Radio Raw data Data packet RC5 auth. data RC5 Setup input Intermediate value RC5 Round 16 authenticated output 8 After 8 cycles, the encryption completes and the output becomes valid addr Keytable ROM 16 16

  5. Design/Sim Flow Dataflow verilog Area: 4453 um2 Standard cells: 310 Libraries 0.13um Design Compiler RC5 C code Structure verilog Test Vectors C results Spice results Eq? Verilog2spi Spice File Hspice

  6. Encryption Cost (I) Active Encrypting Energy (8 round + 1 round setup) Power is freq. dependent; energy per operation more meaningful Given 4000J total energy, only 0.2322 yr@1.08V and 73.764 yr@0.3V cont. operation Energy (pJ) Encrypting Energy per ns 320X Red: 125C Blue: 85C Vdd (V)

  7. Encryption Cost (II) Delay (1 round) Vth ~ 0.3V; delay grows drastically near threshold @0.3V, requires 1.62us for encryption (~600kHz) Delay (ns) Vdd (V)

  8. Encryption Cost (III) Active Encrypting ED Product (for 1 round) Sweet spot near 0.6 – 0.8V Given low frequency, choose lowest possible voltage ED (1e-21 J*s) Vdd (V) Red: 125C Blue: 85C

  9. Encryption Cost (IV) *Assume 4000J of total battery energy (…) = circuits at 125C • Measured when CLK off • Non trivial static energy  need to disconnect Vdd when not in use

  10. Conclusion • Strong encryption block with low energy requirement • 320x energy difference between 1.08V and 0.3V • > 70 yrs cont. operation @0.3V Future • Varying RC5 parameters (w/r/k) • Custom design RC5 blocks

More Related