RFR(L): 8069539: RSA acceleration

[Christian Thalinger]

> On May 8, 2015, at 8:59 AM, Andrew Haley <aph at redhat.com> wrote:
> 
> Here is a prototype of what I propose:
> 
> http://cr.openjdk.java.net/~aph/rsa-1/ <http://cr.openjdk.java.net/~aph/rsa-1/>
> It is a JNI version of the fast algorithm I think we should use for
> RSA.  It doesn't use any intrinsics.  But with it, RSA is already twice
> as fast as the code we have now for 1024-bit keys, and almost three
> times as fast for 2048-bit keys!
> 
> This code (montgomery_multiply) is designed to be as easy as I can
> possibly make it to translate into a hand-coded intrinsic.

I’m curious:  did you try to implement this in Java?

>  It will
> then offer better performance still, with the JNI overhead gone and
> with some carefully hand-tweaked memory accesses.  It has a very
> regular structure which should make it fairly easy to turn into a
> software pipeline with overlapped fetching and multiplication,
> although this will perhaps be difficult on register-starved machines
> like the x86.
> 
> The JNI version can still be used for those machines where people
> don't yet want to write a hand-coded intrinsic.
> 
> I haven't yet done anything about Montgomery squaring: it's
> asymptotically 25% faster than Montgomery multiplication.
> 
> I have only written it for x86_64.  Systems without a 64-bit multiply
> won't benefit very much from this idea, but they are pretty much
> legacy anyway: I want to concentrate on 64-bit systems.
> 
> So, shall we go with this?  I don't think you will find any faster way
> to do it.
> 
> Andrew.

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