secp256k1

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Faster const-time modinv divsteps

16

Changes to _divsteps_59 (_30) that give maybe 4% speed improvement to const-time modinv on 64 bit. I see a larger gain on 32 bit but measured on 64 bit so...

peterdettman

Investigate using new algorithm for scalar multiplication

3

>This is an algorithm for EC multiplication that emulates the Montgomery Ladder double-and-add, but in a constant time way. An early version of this algorithm was published in 2017, and...

paulmillr

x-only ECDH support

10

Technically this isn't required: you can always implement an x-only hashfn yourself, and convert to a compressed pubkey to call secp256k1_ecdh(). But I'm not smart enough to figure that out...

rustyrussell

Convert `secp256k1_xonly_pubkey` to `secp256k1_pubkey`

2

Is there a way to convert a `secp256k1_xonly_pubkey` into a `secp256k1_pubkey` ? Reason: Extract `secp256k1_xonly_pubkey` from a P2TR address and use it as parameter to `secp256k1_ecdh()`. Edit: Seem related. https://github.com/bitcoin-core/secp256k1/pull/994...

w0xlt

Don't #include standard library headers unconditionally

6

We currently include for `fprintf` used in the a) tests and b) in the default error callbacks ... We should not include the header unconditionally. https://github.com/bitcoin-core/secp256k1/blob/912b7ccc4473b5c969b01d027b8d5dc515435eb5/src/util.h#L16 This is a problem...

real-or-random

ci: Optimize build matrix

2

We should try to merge #995 before this PR to avoid conflicts. This tries to get more coverage of "useful" configurations with fewer tasks. I think what I suggest here...

real-or-random

group: Save a normalize_to_zero in gej_add_ge

2

As discovered by @sipa in #1033. See commit message for reasoning but note that the infinity handling will be replaced in the second commit again.

real-or-random

cross-testing

15

In #635 I was convinced that cross-testing is a good thing. It would be nice to have cross tests for - https://github.com/elichai/ecc-secp256k1 as inspired by the discussion in #635, or...

real-or-random

WIP: Add schnorrsig batch verification

37

This was part of #558 (for 20 months) to demonstrate the advantages of batch verification (see [graph](https://github.com/sipa/bips/blob/bip-schnorr/bip-schnorr.mediawiki#design)), but then removed to simplify #558 because there are still ongoing discussions: -...

jonasnick

Document field functions assumptions and validate it using magnitude and `fe_verify` checks

18

Fixes #946 and #1061 Changes: - update docs to `_fe_equal_var` requires only the first input magnitude to be 1 - removed the `secp256k1_fe_normalize_weak` call for the second argument of `_fe_equal_var`...

siv2r