2022-01-24 12:07:43 +00:00
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# bt\_secp256k1 (Blockchain Tools - secp256k1)
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2022-01-23 05:51:29 +00:00
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2022-01-24 12:07:43 +00:00
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A code-generated single file header for
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[bitcoin-core/secp256k1](https://github.com/bitcoin-core/secp256k1), an
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optimized C library for ECDSA signatures and secret/public key operations on
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curve secp256k1.
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2022-01-23 05:51:29 +00:00
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## Using bt\_secp256k1
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The header files are generated from a metaprogram that is included in this
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repository. To use the library you only need 1 header file of which, 3 variants
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are provided,
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- bt\_secp256k1\_i64.h (USE\_FORCE\_WIDEMUL\_INT64 is defined)
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- bt\_secp256k1\_i128.h (USE\_FORCE\_WIDEMUL\_IN128 is defined)
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- bt\_secp256k1\_i128\_x86\_64\_asm.h (USE\_FORCE\_WIDEMUL\_IN128 & USE\_ASM\_X86\_64 is defined)
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Given the 3 variants, for optimal performance choose the most featureful variant
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that your platform supports.
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In exactly one `.c` or `.cpp` file that includes `bt_secp256k1.h` define
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`BT_SECP256K1_IMPLEMENTATION` as per follows (with additional options to
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configure the library via macros, see the single file headers for more
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definitive explanations).
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```cpp
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#define BT_SECP256K1_IMPLEMENTATION
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#define ECMULT_GEN_PREC_BITS 4
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#define ECMULT_WINDOW_SIZE 15
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#include "bt_secp256k1_i64.h"
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```
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## Details
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The metaprogram provided in `bt_secp256k1_metaprogam.cpp` is responsible for
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collating code files and patching source files to ensure the project can be
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combined into a single header file, generating the output files.
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The code generated header files vendored in the repository correspond to the
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current commit hash checked out from the secp256k1 submodule.
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An example program `bt_secp256k1_example.c` is provided that implements a basic
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secp256k1 keypair generator for reference and testing the single header file
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compilation.
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2022-01-24 12:07:43 +00:00
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## Build
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The build is currently tested on Windows Visual Studio 2019's `cl` via
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`build.bat` which will build the metaprogram and generate the single header
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files.
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Examples are built using `build_examples.bat` and optionally invoke `clang-cl`
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if it's available on the path.
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2022-01-23 05:51:29 +00:00
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## License
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2022-01-24 12:07:43 +00:00
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The single file header code-generator metaprogram is provided under the
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Unlicense license.
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2022-01-23 05:51:29 +00:00
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This is free and unencumbered software released into the public domain.
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Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
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software, either in source code form or as a compiled binary, for any purpose,
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commercial or non-commercial, and by any means.
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2022-01-24 12:07:43 +00:00
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bitcoin-core/secp256k1 is provided under its original license and is embedded in
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the single-file-header.
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