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Hash Function Performance Metrics
GMU SHA Core Interface & Hash Function Performance Metrics
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Interface
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Why Interface Matters? Pin limit Support for the maximum throughput
Total number of i/o ports ≤ Total number of an FPGA i/o pins Support for the maximum throughput Time to load the next message block ≤ Time to process current block
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Interface: Two possible solutions
msg_bitlen SHA core message end_of_msg zero_word Length of the message communicated at the beginning Dedicated end-of-message port + easy to implement passive source circuit − area overhead for the counter of message bits − more intelligent source circuit required + no need for internal message bit counter
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SHA Core: Interface & Typical Configuration
clk rst clk rst clk rst clk rst clk rst clk rst Input FIFO SHA core Output FIFO ext_idata idata odata ext_odata din dout din dout din dout w w w w fifoin_full fifoin_empty fifoout_full fifoout_empty full empty src_ready dst_ready full empty fifoin_write fifoin_read fifoout_write fifoout_read write read src_read dst_write write read SHA core is an active component; surrounding FIFOs are passive and widely available Input interface is separate from an output interface Processing a current block, reading the next block, and storing a result for the previous message can be all done in parallel
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SHA Core Interface SHA core w din dout src_ready src_read dst_ready
dst_write clk rst
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SHA Core Interface + Surrounding FIFOs
fifoin_empty fifoin_read idata w odata fifoout_full fifoout_write fifoin_full fifoin_write fifoout_empty fifoout_read Input FIFO SHA core clk rst ext_idata ext_odata din dout src_ready src_read dst_ready dst_write full empty write read Output
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Operation of FIFO
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Communication Protocol for Unpadded Messages
msg_bitlen zero_word −−−−− message w bits . seg_0_bitlen seg_0 seg_1_bitlen seg_1 seg_n-1_bitlen seg_n-1 a) b)
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SHA Core Interface with Additional Faster I/O Clock
din dout src_ready src_read dst_ready dst_write clk rst io_clk
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SHA Core Interface with Two Clocks + Surrounding FIFOs
fifoin_empty fifoin_read idata w odata fifoout_full fifoout_write fifoin_full fifoin_write fifoout_empty fifoout_read Input FIFO SHA core clk rst ext_idata ext_odata din dout src_ready src_read dst_ready dst_write full empty write read Output io_clk
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Communication Protocol for Padded Messages Without Message Splitting
w bits msg_len_ap | last = 1 msg_len_bp message msg_len_ap – message length after padding [bits] msg_len_bp – message length before padding [bits]
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Communication Protocol for Padded Messages With Message Splitting
. seg_0_len_ap | last=0 seg_0 w bits seg_1_len_ap | last=0 seg_1 seg_n-1_len_ap | last=1 seg_n-1 seg_n-1_len_bp seg_i_len_ap – segment i length after padding* [bits] seg_i_len_bp – segment i length before padding [bits] * For all i < n-1 segment i length after padding is assumed to be a multiple of the message block size, b [characteristic to each function], and thus also the word size, w. The last segment cannot consist of only padding bits. It must include at least one message bit.
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Performance Metrics
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Performance Metrics - Speed
Throughput for Long Messages [Mbit/s] Throughput for Short Messages [Mbit/s] Execution Time for Short Messages [ns] Allows for easy cross-comparison among implementations in software (microprocessors), FPGAs (various vendors), ASICs (various libraries)
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Performance Metrics - Speed
Time to hash N blocks of message [cycles] = Htime(N) The exact formula from analysis of a block diagram, confirmed by functional simulation. Minimum Clock Period [ns] = T From a place & route and/or static timing analysis report file.
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Time to Hash N Blocks of the Message [clock cycles]
![Time to Hash N Blocks of the Message [clock cycles]](http://slideplayer.com./slide/13207579/79/images/17/Time+to+Hash+N+Blocks+of+the+Message+%5Bclock+cycles%5D.jpg "Time to Hash N Blocks of the Message [clock cycles]")
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Performance Metrics - Speed
Minimum time to hash N blocks of message [ns] = Htime(N)⋅T block_size Maximum Throughput (for long messages) = T * (Htime(N+1) - Htime(N)) block_size = T * block_processing_time Effective maximum throughput for short messages:
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Performance Metrics - Speed
from specification Maximum Throughput (for long messages) block_size = T * block_processing_time from place & route report and/or static timing analysis report from analysis of block diagram and/or functional simulation
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Performance Metrics - Area
For the basic, folded, and unrolled architectures, we force these vectors to look as follows through the synthesis and implementation options: Areaa
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Choice of Optimization Target
Primary Optimization Target: Throughput to Area Ratio Features: practical: good balance between speed and cost very reliable guide through the entire design process, facilitating the choice of high-level architecture implementation of basic components choice of tool options leads to high-speed, close-to-maximum-throughput designs
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Our Design Flow Specification Interface Controller Template Datapath
Block diagram Controller ASM Chart Library of Basic Components VHDL Code Formulas for Throughput & Hash time Max. Clock Freq. Resource Utilization Throughput, Area, Throughput/Area, Hash Time for Short Messages
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How to compare hardware speed vs. software speed?
EBASH reports ( In graphs Time(n) = Time in clock cycles vs. message size in bytes for n-byte messages, with n=0,1, 2, 3, … 2048, 4096 In tables Performance in cycles/byte for n=8, 64, 576, 1536, 4096, long msg Time(4096) – Time(2048) Performance for long message = 2048
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How to compare hardware speed vs. software speed?
8 bits/byte ⋅ clock frequency [GHz] Throughput [Gbit/s] = Performance for long message [cycles/byte]
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