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PBKDF2 Accelerator Design Review

Akshay Sahni, William Ehlhardt, Yicheng Guo. PBKDF2 Accelerator Design Review. Overview. It implements a particular PBKDF in hardware via ASIC to significantly erode the computational cost We would implement PBKDF2 using the HMAC-SHA1 pseudorandom function

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PBKDF2 Accelerator Design Review

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  1. Akshay Sahni, William Ehlhardt, Yicheng Guo PBKDF2 AcceleratorDesign Review

  2. Overview • It implements a particular PBKDF in hardware via ASIC to significantly erode the computational cost • We would implement PBKDF2 using the HMAC-SHA1 pseudorandom function • PBKDF2 is a key derivation function that is a part of RSA labs Public-Key Cryptography Standards series. • PBKDF2 applies a pseudorandom function, such as SHA-1 to the input password along with a salt value and repeats the process many times to produce a Derived Key. • Derived Key can then be used as a cryptographic key in subsequent operations. • The added computational work makes password cracking much more difficult, and is known as key stretching.

  3. PBKDF2-HMAC-SHA1 on an ASIC PBKDF2(P, S, c, dkLen) Ko U1 c Host ASIC F(Ko, U1, c) PRF(Ko, data) = HMAC(Ko, data) SHA-1

  4. System Interface I

  5. System Interface II

  6. Flow Chart I

  7. Flow Chart II

  8. Architecture Diagram

  9. Falling Edge Detect Block • The Falling Edge Detect Block will detect any falling edge on the input IE signal • Once a falling edge on IE signal is detected, it will assert GO signal high for one clock cycle. clk PrevBit clk RN_Prevbit GO Output Logic RST_N Register RST_N IE Register RN_PrevBit

  10. Input Shift Register Block • This Block will function as a buffer to receive all 88 bytes of input signals from the 32-bit bidirectional data bus. • As long as the IE signal is high, it will shift 4 bytes of signal on the data bus to other functional blocks in the chip. IE 88 Byte Shit Register BUS_IN K0 32 512 CLK U1 160 RST_N C 32

  11. Output Shift Register Block • This block functions as an output buffer • When it is enabled by the Output Enable(OE)signal, will shift the data onto the 32-bit data bus. SR_LOAD 20 Byte Shit Register ACC 160 BUS_OUT CLK 32 RST_N OE

  12. HashPrep Block • Generates the next 672 bit vector to be hashed HPSTEP XOR OPAD 512 672 K0 HRES 1 HDATA 512 672 512 0 IPAD XOR 672 UI

  13. Hash Block HDATA<671:160> HDATA<159:0> Padding ChunkID 0 1 Round CTR HRES F / K Computation WordExt Stir

  14. Accumulator Block • It keeps track of the following: • Each UI vector • Accumulated xor result of precious ACC signal • New HRES signal GO STATE register Next count logic ACC ACC_STROBE 2 NEXT_STATE 160 160 UI ACC_NXT 160 UI next logic 160 HRES UI_NXT ACC_nxt_logic HRES 160 160 U1 160

  15. Counter Block • Counts the number of inner PRF iterations performed • When iterations equal the required by the input, it asserts CNTDONE • CNTDONE stops the PBKDF2 algorithm GO COUNT COUNT Next count logic register register INCR 32 32 CNTDONE CNTDONE_NXT COUNT Comparator Comparator 32 32 C C 32 32

  16. Control Unit Block • This block functions as a state machine to control the operation by the other blocks on the chip GO Next state logic HRDY OE CNTDONE INCR Output Logic SR_LOAD CLK register HPSTEP ACC_STROBE STATE RESULT_READY NEXTSTATE 4 IDLE 4 HRUN RST_N

  17. Area Budgeting Table Timing Budgeting Table

  18. Questions (and Answers!)

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