bc61b91 add pubkey prefix constants to include/secp256k1.h (Andrew Poelstra)
Pull request description:
In future multisig implementations we will need to pass nonces around, which are algebraically pubkeys but should not be decodable as pubkeys. The way to do this is to change the prefix byte from the ordinary 0x02/0x03 to something else. However, some forks (notably `secp256k1-zkp`) have started using some bytes for their own encodings, and if we continue to use hardcoded constants the risk of conflict is increased.
This commit puts the prefixes used by the main library into the `include/secp256k1.h` so that the constants we're using will at least be in a standard easy-to-reference place.
Tree-SHA512: 37fa25be5074b7c519a9c69421320a62f32a3818f144254eb57f96c6657b993fc01962a5c670574275d1c59b095a6c89e60736123f032d6736907284eac526d7
768514b Fix wnaf_const documentation with respect to return value and number of words set (Jonas Nick)
Pull request description:
Tree-SHA512: e2e49036c5930c74fff12626957a43000e5f86180791f2b857d279e83c609663ee5cbee4c3380f3df3d29e493f40051d63a8eff1badeea99e06652d9e72f4d29
5e95bf2 Remove residual parts from the schnorr expirement. (Gregory Maxwell)
Tree-SHA512: de1e56cc54443e29a60787996a1b1381b0b84eacb87a8f1af06b5ba3900b1771c3a04fd547c65e21979e3c08c3a45d258d699eb951a956f8e617833c5396ecfe
465159c Further shorten the addition chain for scalar inversion. (Brian Smith)
cf12fa1 Minor optimizations to _scalar_inverse to save 4M (Peter Dettman)
Tree-SHA512: b03ae53bd48435f8ef8a89ba3b45f9a35f3f3c6cfba7deb6820ab2146205656d198e4317a4cb98a986f434df244ae735313d303d0ce5a5c40519d37621238957
field_get_b32: min 0.890us / avg 0.905us / max 0.956us
field_set_b32: min 1.12us / avg 1.15us / max 1.19us
becomes
field_get_b32: min 0us / avg 0.000000119us / max 0.000000238us
field_set_b32: min 0.0532us / avg 0.0584us / max 0.0782us
field_get_b32: min 0.647us / avg 0.666us / max 0.751us
field_set_b32: min 0.551us / avg 0.571us / max 0.624us
becomes
field_get_b32: min 0us / avg 0.0000000477us / max 0.000000238us
field_set_b32: min 0us / avg 0.0000000238us / max 0.000000238us
(Patch from https://bitcointalk.org/index.php?topic=1740973.0
_get was reversed from the patch because this order appeared
somewhat faster in testing.)
Signed-off-by: Gregory Maxwell <greg@xiph.org>
5eb030c test: Use checked_alloc (Wladimir J. van der Laan)
Tree-SHA512: f0fada02664fca3b4f48795ce29a187331f86f80fc1605150fcfc451e7eb4671f7b5dff09105c9927e28af6d1dafd1edad1671dddd412110f4b5950153df499d
I think I summarized it correctly after IRC discussion with gmaxwell
and andytoshi; I didn't know it existed :(
It's regrettable to expose this level of detail, but users need to know
this to make a decision about how to use it.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
OpenSSL 1.1 makes ECDSA_SIG opaque and our tests need access
inside this object.
The comparison tests against OpenSSL aren't important for most
users, but the build failing is...
Mathematically, we always overflow when using the exhaustive tests (because our
scalar order is 13 and our field order is on the order of 2^256), but the
`overflow` variable returned when parsing a b32 as a scalar is always set
to 0, to prevent infinite (or practically infinite) loops searching for
non-overflowing scalars.
Whenever ecdsa_sig_sign is called, in the case that r == 0 or r overflows,
we want to retry with a different nonce rather than fail signing entirely.
Because of this, we always check the nonce conditions before calling
sig_sign, so these checks should always pass (and in particular, they
are inaccessible through the API and appear as uncovered code in test
coverage).
b4ceedf Add exhaustive test for verification (Andrew Poelstra)
83836a9 Add exhaustive tests for group arithmetic, signing, and ecmult on a small group (Andrew Poelstra)
20b8877 Add exhaustive test for group functions on a low-order subgroup (Andrew Poelstra)
If you compile without ./configure --enable-exhaustive-tests=no,
this will create a binary ./exhaustive_tests which will execute
every function possible on a group of small order obtained by
moving to a twist of our curve and locating a generator of small
order.
Currently defaults to order 13, though by changing some #ifdefs
you can get a couple other ones. (Currently 199, which will take
forever to run, and 14, which won't work because it's composite.)
TODO exhaustive tests for the various modules
We observe that when changing the b-value in the elliptic curve formula
`y^2 = x^3 + ax + b`, the group law is unchanged. Therefore our functions
for secp256k1 will be correct if and only if they are correct when applied
to the curve defined by `y^2 = x^3 + 4` defined over the same field. This
curve has a point P of order 199.
This commit adds a test which computes the subgroup generated by P and
exhaustively checks that addition of every pair of points gives the correct
result.
Unfortunately we cannot test const-time scalar multiplication by the same
mechanism. The reason is that these ecmult functions both compute a wNAF
representation of the scalar, and this representation is tied to the order
of the group.
Testing with the incomplete version of gej_add_ge (found in 5de4c5dff^)
shows that this detects the incompleteness when adding P - 106P, which
is exactly what we expected since 106 is a cube root of 1 mod 199.
Pieter Wuille
Jonas Nick
Dag Robole
Andrew Poelstra
Tim Ruffing
Gregory Maxwell
Brian Smith
CryptoGuru
Peter Dettman
Emil Rus
Wladimir J. van der Laan
Rusty Russell
practicalswift