If the generator point multiplication result in Jacobian coordinates is
immediately converted to affine coordinates after and is not needed for
anything else, we can deduplicate by using the helper introduced in #1861.
Note that in a very strict sense this is not a refactor, as the Jacobian
object is now cleared out which was not done on master, but for the logic
in the tests this shouldn't matter at all.
Now that we have a function `_ecmult_gen_ge`, it makes sense to rename
the existing function `_ecmult_gen` to `_ecmult_gen_gej` for
consistency, to signal that the result is a Jacobian group element.
This diff was created by applying
```
$ sed -i s/secp256k1_ecmult_gen\(/secp256k1_ecmult_gen_gej\(/g $(git ls-files)
```
This removes printing of the "random run = " at the end of the tests. I
haven't seen a single case where this proved to be useful. And as of
48789dafc2, this is anyway printed only at
the end of the exhaustive tests and not the normal tests, so the
probability that this will be useful in the future is very low.
This introduces the signed-digit multi-comb multiplication algorithm
for constant-time G multiplications (ecmult_gen). It is based on
section 3.3 of "Fast and compact elliptic-curve cryptography" by
Mike Hamburg (see https://eprint.iacr.org/2012/309).
Original implementation by Peter Dettman, with changes by Pieter Wuille
to use scalars for recoding, and additional comments.
`random_fe_non_zero` contains a loop iteration limit that ensures that
we abort if `random_fe` ever yielded zero more than ten times in a row.
This construct was first introduced in PR #19 (commit 09ca4f32) for
random non-square field elements and was later refactored into the
non-zero helper in PR #25 (commit 6d6102fe). The copy-over to the
exhaustive tests happened recently in PR #1118 (commit 0f864207).
This case seems to be practically irrelevant and I'd argue for keeping
things simple and removing it; if there's really a worry that the test's
random generator is heavily biased towards certain values or value
ranges then there should consequently be checks at other places too
(e.g. directly in `random_fe` for 256-bit values that repeatedly
overflow, i.e. >= p).
Also, the _fe_normalize call is not needed and can be removed, as the
result of `random_fe` is already normalized.
It is not neccessary for the second argument in `secp256k1_fe_equal_var`
(or `secp256k1_fe_equal`) to have magnitude = 1.
Hence, removed the `secp256k1_fe_normalize_weak` call for those argument.
Infinity isn't currently needed here, but correctly handling it is a
little more safe against future changes.
Update docs for it to make it clear that it is not constant time in A
(the input point). It never was constant time in Q (and would be a little
complicated to make constant time in A).
If it was later made constant time in A, infinity support would be easy
to preserve, e.g. by running it on a dummy value and cmoving infinity into
the output.
8e142ca410 Move `SECP256K1_INLINE` macro definition out from `include/secp256k1.h` (Hennadii Stepanov)
77445898a5 Remove `SECP256K1_INLINE` usage from examples (Hennadii Stepanov)
Pull request description:
From [IRC](https://gnusha.org/secp256k1/2023-01-31.log):
> 06:29 \< hebasto\> What are reasons to define the `SECP256K1_INLINE` macro in user's `include/secp256k1.h` header, while it is used internally only?
> 06:32 \< hebasto\> I mean, any other (or a new dedicated) header in `src` looks more appropriate, no?
> 06:35 \< sipa\> I think it may just predate any "utility" internal headers.
> 06:42 \< sipa\> I think it makes sense to move it to util.h
Pros:
- it is a step in direction to better organized headers (in context of #924, #1039)
Cons:
- code duplication for `SECP256K1_GNUC_PREREQ` macro
ACKs for top commit:
sipa:
utACK 8e142ca410
real-or-random:
utACK https://github.com/bitcoin-core/secp256k1/pull/1231/commits/8e142ca4102ade1b90dcb06d6c78405ef3220599
Tree-SHA512: 180e0ba7c2ef242b765f20698b67d06c492b7b70866c21db27c18d8b2e85c3e11f86c6cb99ffa88bbd23891ce3ee8a24bc528f2c91167ec2fddc167463f78eac
This change eases the use of alternate build systems by moving
the variables in `src/libsecp256k1-config.h` to compiler macros
for each invocation, preventing duplication of these variables
for each build system.
Co-authored-by: Ali Sherief <ali@notatether.com>
This simplifies building without a build system.
This is in line with #925; the paths fixed here were either forgotten
there or only introduced later. This commit also makes the Makefile
stricter so that further "wrong" #include paths will lead to build
errors even in autotools builds.
This belongs to #929.
Co-authored-by: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>
If `secp256k1_ecdsa_sign` fails, the signature which is then loaded by
`secp256k1_ecdsa_signature_load` is garbage. Exit early with an error
when this occurs.
This enables testing overflow is correctly encoded in the recid, and
likely triggers more edge cases.
Also introduce a Sage script to generate the parameters.
kallal79
Sebastian Falbesoner
Tim Ruffing
Pieter Wuille
Peter Dettman
siv2r
Gregory Maxwell
Hennadii Stepanov
Jonas Nick
Russell O'Connor
Nicolas Iooss
William Bright
Dimitris Apostolou