Belgian programmer solves MIT’s 20-year-old time capsule cryptographic puzzle

Re:Belgian programmer solves MIT’s 20-year-old time capsule ... by docbrown on Tuesday April 30, 2019 @01:52AM (#19785453)

>Although Rivest initially released the puzzle’s code in Java, Fabrot realized it could be solved faster if he used the GNU Multiple Precision Arithmetic Library, free software written in C for doing “precise arithmetic.” So Fabrot dedicated one of the CPU cores on his home desktop computer to running squaring operations in an attempt to solve the puzzle. He says his computer was running the operation 24/7, except when he would have to leave on vacation or there was a power outage.

It seems as if your 2014 comment hinted at this project. Applause for keeping this tight lipped for those years.

2014 comment: >Java is quite fast compared to most languages but for some things it is still terribly slow compared to C / C++. I had to do some big integers crunching lately and tried: Java, Go, Go with GMP, C (GMP) and Haskell (using GMP under the hood). Eventually I went for good old C with the latest GMP version for it was the fastest for my use case (with Haskell and Go with GMP coming close but still not as fast as C). Java was, for the computation I needed to do... Eight times slower than C! I know I was hitting a edge case for a very specific kind of computation but still. [0]

[0]: https://news.ycombinator.com/item?id=7979006

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Re:Belgian programmer solves MIT’s 20-year-old time capsule ... by rich-tea on Tuesday April 30, 2019 @03:20AM (#19785789)

Just want to add that GMP is not "C". The critical parts are written in assembly. It's not really possible to do fast multiple-precision arithmetic in C. You need direct access to add with carry instructions and the like.

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Re:Belgian programmer solves MIT’s 20-year-old time capsule ... by GordonS on Tuesday April 30, 2019 @03:30AM (#19785833)

Yes, access to hardware intrinsics is what can really accelerate arithmetic - C makes this pretty easy though.

As an aside, .NET Core 3.0 will deliver access to intrinsics - not sure if Java or any other managed platform already has this?

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Re:Belgian programmer solves MIT’s 20-year-old time capsule ... by TacticalCoder on Thursday May 02, 2019 @08:07AM (#19806949)

Your nick sounds familiar. "richtea" I'd say I remember but no idea from where.

Yeah I'm sorry that my comment from late 2014 gave that false impression that I said GMP was written in C. What I meant was that it was, when I did the testing, slightly faster to call GMP from C than from Haskell, Clojure, Java. I remember I tried all these back then and calling GMP for C was a bit more efficient. Now I know there are now ways to call libs like this from Java without paying the old foreign function call penalty: but I didn't know about that in 2014. So I called GMP from C because it was faster. Out of memory I'd have said GMP was C with inline assembly but I may be wrong ; )

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Re:Belgian programmer solves MIT’s 20-year-old time capsule ... by rich-tea on Thursday May 02, 2019 @01:55PM (#19810561)

Most of it is just straight up assembly. I don't think there's much inline assembly because that's hard to maintain for multiple platforms.

Rich Tea is a British biscuit. Maybe that's why you remember it?

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