It is a non-Libtool-specific way to explicitly specify the user's
intention to consume a static `libseck256k1`.
This change allows to get rid of MSVC linker warnings LNK4217 and
LNK4286. Also, it makes possible to merge the `SECP256K1_API` and
`SECP256K1_API_VAR` into one.
The scheme implemented is described below, and largely follows the paper
"SwiftEC: Shallue–van de Woestijne Indifferentiable Function To Elliptic Curves",
by Chavez-Saab, Rodriguez-Henriquez, and Tibouchi
(https://eprint.iacr.org/2022/759).
A new 64-byte public key format is introduced, with the property that *every*
64-byte array is an encoding for a non-infinite curve point. Each curve point
has roughly 2^256 distinct encodings. This permits disguising public keys as
uniformly random bytes.
The new API functions:
* secp256k1_ellswift_encode: convert a normal public key to an ellswift 64-byte
public key, using additional entropy to pick among the many possible
encodings.
* secp256k1_ellswift_decode: convert an ellswift 64-byte public key to a normal
public key.
* secp256k1_ellswift_create: a faster and safer equivalent to calling
secp256k1_ec_pubkey_create + secp256k1_ellswift_encode.
* secp256k1_ellswift_xdh: x-only ECDH directly on ellswift 64-byte public keys,
where the key encodings are fed to the hash function.
The scheme itself is documented in secp256k1_ellswift.h.
This warns on certain identifiers reserved by the C standard, namely
* identifiers that begin with an underscore followed by an uppercase
letter, and
* identifiers in the global namespace that begin with an underscore.
We had used such identifiers in the past for macros in include guards,
and we should make sure that we don't reintroduce such identifiers
going forward.
Note that C reserves more identifiers for "future library directions",
e.g., identifiers that begin with "str" followed by a lowercase letter.
But even the C standards committee has decided that this is somewhat
silly and adopted a proposal [1] for C23 that removes the restriction
that programs using these identifiers have UB. Instead, these
identifiers are now "potentially reserved", which is not a normative
restriction but simply an informative warning that the identifiers
may become fully reserved in the future.
[1] https://www.open-std.org/jtc1/sc22/WG14/www/docs/n2625.pdf
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>
There are plenty of unreleased variants of libsecp256k1 version 0.1.0
(libsecp256k1.so.0.0.0) in the wild. We choose a new version number to allow a
clear distinction.
There are variants of 0.1.0 that are incompatible with the initial release,
hence we increase the minor version to arrive at version number 0.2.0. For the
same reason, we increase the LIB_VERSION_CURRENT and keep AGE at 0.
The changelog for 0.2.0 consists of the relevant changes since 2021-12-25, which
is the date when the initial release process PR was merged (and the library
version was set to a pre-release, see 423b6d19d373f1224fd671a982584d7e7900bc93).
This is somewhat arbitrary but at least points readers to relevant changes.
41e8704b484652cf5bbb2b7ecc27feedc3cf0ae1 build: Enable some modules by default (Tim Ruffing)
Pull request description:
This has been discussed in https://github.com/bitcoin-core/secp256k1/issues/817#issuecomment-693198323 and I agree with the arguments brought up there.
Alternatively, we could not enable them and add a discussion to the readme why we discourage people from using the modules. I believe enabling ECDH is not very controversial. But what about recovery? Do we want to leave it off and instead give a reason?
ACKs for top commit:
sipa:
ACK 41e8704b484652cf5bbb2b7ecc27feedc3cf0ae1
jonasnick:
ACK 41e8704b484652cf5bbb2b7ecc27feedc3cf0ae1
Tree-SHA512: 1dd21037043f2b2c94a92cd2f31e69b505ba5b43119897bc0934966d9ccd84fc4fc20e7509af634f1c3a096710db1a2253090f5f1f107b9d258945a5546e9ba4
We don't enable the ECDSA recovery module, because we don't recommend
ECDSA recovery for new protocols. In particular, the recovery API is
prone to misuse: It invites the caller to forget to check the public
key (and the verification function always returns 1).
In general, we also don't recommend ordinary ECDSA for new protocols.
But disabling the ECDSA functions is not possible because they're not
in a module, and let's be honest: disabling ECDSA would mean to ignore
reality blatantly.
We had removed `PKG_PROG_PKG_CONFIG` in 21b2ebaf74222017f85123deb6f30a33c7678513
(#1090). But then then the not rebased (!) merge of 2be6ba0fedd0d2d62ba6f346d7ced7abde0d66e4
(#1084) brought that macro back at another location, without git
complaining about a conflict.
Fixes#1127.
49e2acd927ce9eb806cc10f3a1fd89a9ddd081e2 configure: Improve rationale for WERROR_CFLAGS (Tim Ruffing)
8dc4b03341c85a3be91e559d05771c51e60b0eba ci: Add a C++ job that compiles the public headers without -fpermissive (Tim Ruffing)
51f296a46c0b318b8dd572ef9ac3bb3a4140ae63 ci: Run persistent wineserver to speed up wine (Tim Ruffing)
3fb3269c22c25de3b720ad139dcf4e3cff9eda1a ci: Add 32-bit MinGW64 build (Tim Ruffing)
9efc2e5221560d19dd750e0ba32c03d4ee091227 ci: Add MSVC builds (Tim Ruffing)
2be6ba0fedd0d2d62ba6f346d7ced7abde0d66e4 configure: Convince autotools to work with MSVC's archiver lib.exe (Tim Ruffing)
bd81f4140a4228b1df3a9f631e2d207a197ae614 schnorrsig bench: Suppress a stupid warning in MSVC (Tim Ruffing)
09f3d71c51a9621653d766e2fe7e657534e57bd6 configure: Add a few CFLAGS for MSVC (Tim Ruffing)
3b4f3d0d46dd278fbe4ffa68b1b6e14e3ea3b17f build: Reject C++ compilers in the preprocessor (Tim Ruffing)
1cc09414149d0c0c6a4a500d83efc3bd66f3ebcd configure: Don't abort if the compiler does not define __STDC__ (Tim Ruffing)
cca8cbbac84624fd350efc4086af25a06dcf8090 configure: Output message when checking for valgrind (Tim Ruffing)
1a6be5745fcf9f90e4218b73712b71ea06361792 bench: Make benchmarks compile on MSVC (Tim Ruffing)
Pull request description:
ACKs for top commit:
jonasnick:
ACK 49e2acd927ce9eb806cc10f3a1fd89a9ddd081e2
Tree-SHA512: 986c498fb218231fff3519167d34a92e11dea6a4383788a9723be105c20578cd483c6b06ba5686c6669e3a02cfeebc29b8e5f1428552ebf4ec67fa7a86957548
