This also makes the order in which module options are processed
consistent between CMake and autotools (the reverse order of the listing
printed to stdout).
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.
71f746c057a66d5ae0dfdb5d439bc49592c0d16e cmake: Include `include` directory for subtree builds (Hennadii Stepanov)
5431b9decdbbdf30c5c5f2aed4b59662f5c681a2 cmake: Make `SECP256K1_INSTALL` default depend on `PROJECT_IS_TOP_LEVEL` (Hennadii Stepanov)
162608cc982538906e775d0c549aff2de5dee413 cmake: Emulate `PROJECT_IS_TOP_LEVEL` for CMake<3.21 (Hennadii Stepanov)
Pull request description:
This PR:
1. Emulates [`PROJECT_IS_TOP_LEVEL`](https://cmake.org/cmake/help/latest/variable/PROJECT_IS_TOP_LEVEL.html) variable for CMake versions where it is not available.
2. Makes the `SECP256K1_INSTALL` option dependent on `PROJECT_IS_TOP_LEVEL` (a [follow up](https://github.com/bitcoin-core/secp256k1/pull/1263#issuecomment-1516564300) of https://github.com/bitcoin-core/secp256k1/pull/1263).
3. Makes integration of this project as a subtree easier. A top project can `#include <secp256k1.h>` with no additional `target_include_directories()` commands. For example, see https://github.com/hebasto/secp256k1-CMake-example/tree/subtree.
ACKs for top commit:
theuni:
utACK 71f746c057a66d5ae0dfdb5d439bc49592c0d16e.
Tree-SHA512: 8ccdbcc94b26f36e772611ebaab0f2846debd6ad20f9e361be31a8d2128a14273acb692b0631026e12cc6cdef6d445dce0fd3beb4f71af47b46dfcf840a18879
ef49a11d29601e09e94134975c968e92c0214102 build: allow static or shared but not both (Cory Fields)
36b0adf1b90139a41fdcb94390d0bb06e9224795 build: remove warning until it's reproducible (Cory Fields)
Pull request description:
Continuing from here: https://github.com/bitcoin-core/secp256k1/issues/1224#issuecomment-1460438227
Unfortunately it wasn't really possible to keep a clean diff here because of the nature of the change. I suggest reviewing the lib creation stuff in its entirety, sorry about that :\
Rather than allowing for shared and static libs to be built at the same time like autotools, this PR switches to the CMake convention of allowing only 1.
A new `BUILD_SHARED_LIBS` option is added to match CMake convention, as well as a `SECP256K1_DISABLE_SHARED` option which overrides it. That way even projects which have `BUILD_SHARED_LIBS=1` can opt-into a static libsecp in particular.
Details:
Two object libraries are created: `secp256k1_asm` and `secp256k1_precomputed_objs`. Some tests/benchmarks use the object libraries directly, some link against the real lib: `secp256k1`.
Because the objs don't know what they're going to be linked into, they need to be told how to deal with PIC.
The `DEFINE_SYMBOL` property sets the `DLL_EXPORT` define as necessary (when building a shared lib)
ACKs for top commit:
hebasto:
re-ACK ef49a11d29601e09e94134975c968e92c0214102, only [suggested](https://github.com/bitcoin-core/secp256k1/pull/1230#pullrequestreview-1388191165) changes since my recent [review](https://github.com/bitcoin-core/secp256k1/pull/1230#pullrequestreview-1352125381).
real-or-random:
ACK ef49a11d29601e09e94134975c968e92c0214102
Tree-SHA512: 8870de305176fdb677caff0fdfc6f8c59c0e906489cb72bc9980e551002812685e59e20d731f2a82e33628bdfbb7261eafd6f228038cad3ec83bd74335959600
5bb03c29116409ace8855e64bf2e2b2d45871469 Replace `SECP256K1_ECMULT_TABLE_VERIFY` macro by a function (Hennadii Stepanov)
4429a8c218d7bf7bc6de1de88bc31c834f771385 Suppress `-Wunused-parameter` when building for coverage analysis (Hennadii Stepanov)
Pull request description:
ACKs for top commit:
real-or-random:
utACK 5bb03c29116409ace8855e64bf2e2b2d45871469
jonasnick:
ACK 5bb03c29116409ace8855e64bf2e2b2d45871469
Tree-SHA512: 19a395434ecefea201a03fc45b3f0b88f1520908926ac1207bbc6570034b1141b49c3c98e66819dcd9069dfdd28c7c6fbe957f13fb6bd178fd57ce65bfbb8fbd
