The Pairing-Based Cryptography Library

News Archive 7

Released pbc-0.4.8

Applied patch by Joe Cooley that addresses issues and fixes a bug in example/zss.c.

Fri Mar 16 01:08:52 PDT 2007

Released pbc-0.4.7

A fairly lowlevel bug had somehow escaped my attention for quite some time. Comparing zero elements previously returned the wrong result, due to a simple logic bug in montfp.c.

Simple final powering optimizations were applied to D and G pairings.

Tue Feb 6 18:36:01 PST 2007

Released pbc-0.4.6

Fortunately for me, Paul Miller tests each version extensively soon after release. In version 0.4.5 he found a bug that I had overlooked for one of the usual reasons: "the modification is so trivial that it can’t possibly cause problems!". Luckily the bug wasn’t difficult to fix.

I finally implemented what I call type G pairings, which are curves of embedding degree 10 found by David Freeman.

They’re a bit slow at the moment, but I hope to speed them up soon. Interestingly, Katherine Stange’s elliptic net algorithm for computing a type G pairing is about the same speed as Miller’s algorithm, but this is without using (signed) sliding windows for the latter.

Fri Feb 2 18:04:45 PST 2007

Released pbc-0.4.5

No big changes. I added code that generates random points by raising a generator by a random power, which is faster in some cases as it avoids finite field square root routines. This change does not affect pairing speed.

I’ve been trying to find a case where computing the pairing with elliptic nets is faster than Miller’s algorithm. I haven’t found one yet, but the type E pairing comes close. If the group order weren’t a Solinas prime then it’s possible that the Shipsey-Stange algorithm would be faster.

Wed Jan 31 16:12:51 PST 2007

Released pbc-0.4.4

Various optimizations improve A, D, E pairing times. In the type E case the optimization was trivial: simply precomputing the random point used in the pairing saved a lot of time.

For type A curves, I implemented an algorithm that computes pairings using elliptic nets: see Katherine Stange’s paper. It is not used by default since it is slower. To activate it, if p is a type A pairing, use:

pairing_option_set(p, "method", "shipsey-stange");

The above paper is accompanied by a PARI/GP script which I used to check against my implementation. I had never used PARI/GP before, and it took me some time to work out what to do. I’ll record what I did here so I won’t have to relearn it next time. First I ran gp with the script as the first argument. Then I typed something like:

Q=[Mod(-x2,q), Mod(y2,q)*a]

Thu Jan 25 05:13:34 PST 2007

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