Parallelizing SHA256 Calculation on FPGA | Hacker News Reader

Parallelizing SHA256 Calculation on FPGA

controlpaths.com

69 pointshasheddan31 comments

So what's the overall hashrate with this approach?

I'll try to calculate it from the information given. 12 parallel instances at a clock speed of 62.5MHz, with 68 clock cycles per hash.

62.5MHz * 12 / 68 = ~11MH/s

That seems... slow? Did I do the math right? How big of an FPGA do you need before this would compete with a GPU, and how much would it cost?

For reference, an RTX 4090 can do 21975.5 MH/s according to hashcat benchmarks.

Quite slow. It's largely due to the author using FPGAs wrong. Clocking down a 7-series Artix to 62.5 MHz means the design is not pipelined correctly/enough. My friend got 1 SHA256 hash per cycle at 300 MHz on 7 series, but slightly fewer of the design fit on a chip. Thruput would easily be in the GH/s range.

Keep in mind RTX4090 is 5 nm process node and has a lot more transistors and memory than XC7A100T, which is 28 nm. That's a huge difference in terms of dynamic performance. Also, the two are also released 10 years apart. If you compare RTX4090 against a similarly modern UltraScale part from Xilinx, I believe the FPGA can be notably faster than RTX4090.

I'm assuming this space has already been heavily optimized by the Bitcoin miners on their way to ASICs.

Yes, but a designed-for-FPGA SHA256 implementation looks very different than an ASIC SHA256 implementation - the ASIC has far greater routing flexibility and density, and can therefore use far more combinatorial logic between register stages.

(ASIC simulation on an FPGA will retain the combinatorial stages but run at dramatically lower fMax)

I should have been a little clearer. I meant that the miners spent a brief period optimizing FPGAs before they abandoned them entirely for ASICs, but during that brief period I'm guessing they squeezed as many hashes/watt out of the FPGAs as they could.

Yes, hard silicon will be another magnitude more performant than FPGAs and GPUs, but ASICs properly take on negative value when they're no longer profitable to mine with. (Note that efficiency won't be much better at the same process node. You can just pump more power through each ASIC die)

Edit - I misread your comment. ASIC designers will use FPGAs to test their design but it won't be optimized for FPGAs which have a different logic-and-memory characteristic than ASICs. There aren't many great SHA256 FPGA implementations, largely because there's not that much demand for one

> but ASICs properly take on negative value when they're no longer profitable to mine with

No matmul coin where the hardware could be repurposed for AI stuff?

Modern BTC ASICs consist of 1600-3200 SHA256 cores and only output nonces for sha256(sha256(btcBlockHeader)) - there's no memory or ability to obtain other output.

always thought it might be cool to repurpose fast double sha engines for error detection in storage arrays

matmul isn't a trapdoor function

Unfortunately I think most of that innovation happened behind closed doors, because everyone wanted to maintain their competitive advantages.

Yes, ASICS are definitely very closed source for that specific reason.

SHA256 is extremely FF-heavy, you need around 200k for an optimized, unrolled, pipelined implementation.

UltraScale+ chips will run a proper design at 600MHz-800MHz, big chips might be able to fit 24 cores. The Artix chip OP used is extremely slow and too small to fit this style of implementation.

More posts like this please! How about a crypto accelerator on FPGA that's integrated with OpenSSL?

Unless you're talking about niche algorithms (and even then), the FPGA will get smoked by a CPU for most common tasks one would use OpenSSL for.

Yes--obviously modern CPUs have crypto extensions that would be faster than an FPGA,this would be for educational purposes.

Even without the extensions, by the time you've moved the workload to the FPGA and back, the CPU has already completed whatever operation your FPGA was going to complete with OpenSSL.

FPGA cryptographic acceleration is about batch task bandwidth, OpenSSL has few places where this is required.

If you want to do crypto acceleration for TLS, there's two places to do it. Handshake/signature/key agreement, which could maybe work, but hasn't been the bottleneck in a long time, eliptic curve dramatically reduces the work for the server and most clients can do it; but maybe shipping the data around for that is fine.

The other part is bulk encryption. CPUs have lots of acceleration for that, but clear text is still faster, so the win is not to ship data to an accelerator and then back to the cpu and then out to the NIC, but to ship to the accelerator and from there to the NIC without touching the CPU or often the accelerator is integrated with the NIC.

It works even better if the data never has to touch the CPU.

Yes, this is why FPGAs are used as NICs in many situations, but the folks doing this are of course not using OpenSSL.

You must be great to talk to at parties lol, I guess I shouldn't build a RISC-V CPU because Intel is faster?

You should definitely build a crypto accelerator - just don't integrate it into OpenSSL (painful codebase to work in, no speed benefit, etc.)

Great job!

For alternative design/writeup, check out http://nsa.unaligned.org

That seems to be the inverse function for SHA-1 and MD5.

If you know the inverse function for SHA-1, that’s really quite something :)

That project is indeed SHA-1 and not SHA256, but the implementation is much more clever and did a very good job utilizing some very ancient FPGAs back in the day.

True.

Now try a fully unrolled/pipelined design that emits one hash per clock cycle for actual parallelization.

Or try hardcoding a few billion trillions of premade hashes

https://en.wikipedia.org/wiki/Rainbow_table ?

It would be called galaxy table

I know why you're downvoted, but it's true, the author is not using FPGAs correctly.

Reply on news.ycombinator.com