rust-secp256k1-unsafe-fast/secp256k1-sys/depend/secp256k1/README.md

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libsecp256k1
============
[![Build Status](https://api.cirrus-ci.com/github/bitcoin-core/secp256k1.svg?branch=master)](https://cirrus-ci.com/github/bitcoin-core/secp256k1)
Upgrade the vendored libsecp256k1 code `libsecp256k1` v0.2.0 was just released. Update the vendored code using `./vendor-libsecp.sh depend 0_8_0 21ffe4b` ``` git show 21ffe4b commit 21ffe4b22a9683cf24ae0763359e401d1284cc7a (tag: v0.2.0) Merge: 8c949f5 e025ccd Author: Pieter Wuille <pieter@wuille.net> Date: Mon Dec 12 17:00:52 2022 -0500 Merge bitcoin-core/secp256k1#1055: Prepare initial release e025ccdf7473702a76bb13d763dc096548ffefba release: prepare for initial release 0.2.0 (Jonas Nick) 6d1784a2e2c1c5a8d89ffb08a7f76fa15e84fff5 build: add missing files to EXTRA_DIST (Jonas Nick) 13bf1b6b324f2ed1c1fb4c8d17a4febd3556839e changelog: make order of change types match keepachangelog.com (Jonas Nick) b1f992a552785395d2e60b10862626fd11f66f84 doc: improve release process (Jonas Nick) ad39e2dc417f85c1577a6a6a9c519f5c60453def build: change package version to 0.1.0-dev (Jonas Nick) 90618e9263ebc2a0d73d487d6d94fd3af96b973c doc: move CHANGELOG from doc/ to root directory (Jonas Nick) Pull request description: Based on #964 ACKs for top commit: sipa: ACK e025ccdf7473702a76bb13d763dc096548ffefba Tree-SHA512: b9ab71d7362537d383a32b5e321ef44069f00e3e92340375bcd662267bc5a60c2bad60222998e6602cfac24ad65efb23d772eac37c86065036b90ef090b54c49 ``` Requires a new version of `secp256k1-sys`, use v0.8.0 - Update the `secp256k1-sys` manifest (including links field) - Update symbols to use 0_8_0 - Add a changelog entry - depend on the new version in `secp256k1` Which in turn requires a new version of `secp256k1`, use v0.26.0
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![Dependencies: None](https://img.shields.io/badge/dependencies-none-success)
[![irc.libera.chat #secp256k1](https://img.shields.io/badge/irc.libera.chat-%23secp256k1-success)](https://web.libera.chat/#secp256k1)
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Optimized C library for ECDSA signatures and secret/public key operations on curve secp256k1.
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This library is intended to be the highest quality publicly available library for cryptography on the secp256k1 curve. However, the primary focus of its development has been for usage in the Bitcoin system and usage unlike Bitcoin's may be less well tested, verified, or suffer from a less well thought out interface. Correct usage requires some care and consideration that the library is fit for your application's purpose.
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Features:
* secp256k1 ECDSA signing/verification and key generation.
* Additive and multiplicative tweaking of secret/public keys.
* Serialization/parsing of secret keys, public keys, signatures.
* Constant time, constant memory access signing and public key generation.
* Derandomized ECDSA (via RFC6979 or with a caller provided function.)
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* Very efficient implementation.
* Suitable for embedded systems.
Upgrade the vendored libsecp256k1 code `libsecp256k1` v0.2.0 was just released. Update the vendored code using `./vendor-libsecp.sh depend 0_8_0 21ffe4b` ``` git show 21ffe4b commit 21ffe4b22a9683cf24ae0763359e401d1284cc7a (tag: v0.2.0) Merge: 8c949f5 e025ccd Author: Pieter Wuille <pieter@wuille.net> Date: Mon Dec 12 17:00:52 2022 -0500 Merge bitcoin-core/secp256k1#1055: Prepare initial release e025ccdf7473702a76bb13d763dc096548ffefba release: prepare for initial release 0.2.0 (Jonas Nick) 6d1784a2e2c1c5a8d89ffb08a7f76fa15e84fff5 build: add missing files to EXTRA_DIST (Jonas Nick) 13bf1b6b324f2ed1c1fb4c8d17a4febd3556839e changelog: make order of change types match keepachangelog.com (Jonas Nick) b1f992a552785395d2e60b10862626fd11f66f84 doc: improve release process (Jonas Nick) ad39e2dc417f85c1577a6a6a9c519f5c60453def build: change package version to 0.1.0-dev (Jonas Nick) 90618e9263ebc2a0d73d487d6d94fd3af96b973c doc: move CHANGELOG from doc/ to root directory (Jonas Nick) Pull request description: Based on #964 ACKs for top commit: sipa: ACK e025ccdf7473702a76bb13d763dc096548ffefba Tree-SHA512: b9ab71d7362537d383a32b5e321ef44069f00e3e92340375bcd662267bc5a60c2bad60222998e6602cfac24ad65efb23d772eac37c86065036b90ef090b54c49 ``` Requires a new version of `secp256k1-sys`, use v0.8.0 - Update the `secp256k1-sys` manifest (including links field) - Update symbols to use 0_8_0 - Add a changelog entry - depend on the new version in `secp256k1` Which in turn requires a new version of `secp256k1`, use v0.26.0
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* No runtime dependencies.
* Optional module for public key recovery.
* Optional module for ECDH key exchange.
Upgrade the vendored libsecp256k1 code `libsecp256k1` v0.2.0 was just released. Update the vendored code using `./vendor-libsecp.sh depend 0_8_0 21ffe4b` ``` git show 21ffe4b commit 21ffe4b22a9683cf24ae0763359e401d1284cc7a (tag: v0.2.0) Merge: 8c949f5 e025ccd Author: Pieter Wuille <pieter@wuille.net> Date: Mon Dec 12 17:00:52 2022 -0500 Merge bitcoin-core/secp256k1#1055: Prepare initial release e025ccdf7473702a76bb13d763dc096548ffefba release: prepare for initial release 0.2.0 (Jonas Nick) 6d1784a2e2c1c5a8d89ffb08a7f76fa15e84fff5 build: add missing files to EXTRA_DIST (Jonas Nick) 13bf1b6b324f2ed1c1fb4c8d17a4febd3556839e changelog: make order of change types match keepachangelog.com (Jonas Nick) b1f992a552785395d2e60b10862626fd11f66f84 doc: improve release process (Jonas Nick) ad39e2dc417f85c1577a6a6a9c519f5c60453def build: change package version to 0.1.0-dev (Jonas Nick) 90618e9263ebc2a0d73d487d6d94fd3af96b973c doc: move CHANGELOG from doc/ to root directory (Jonas Nick) Pull request description: Based on #964 ACKs for top commit: sipa: ACK e025ccdf7473702a76bb13d763dc096548ffefba Tree-SHA512: b9ab71d7362537d383a32b5e321ef44069f00e3e92340375bcd662267bc5a60c2bad60222998e6602cfac24ad65efb23d772eac37c86065036b90ef090b54c49 ``` Requires a new version of `secp256k1-sys`, use v0.8.0 - Update the `secp256k1-sys` manifest (including links field) - Update symbols to use 0_8_0 - Add a changelog entry - depend on the new version in `secp256k1` Which in turn requires a new version of `secp256k1`, use v0.26.0
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* Optional module for Schnorr signatures according to [BIP-340](https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki).
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Implementation details
----------------------
* General
* No runtime heap allocation.
* Extensive testing infrastructure.
* Structured to facilitate review and analysis.
* Intended to be portable to any system with a C89 compiler and uint64_t support.
* No use of floating types.
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* Expose only higher level interfaces to minimize the API surface and improve application security. ("Be difficult to use insecurely.")
* Field operations
* Optimized implementation of arithmetic modulo the curve's field size (2^256 - 0x1000003D1).
* Using 5 52-bit limbs (including hand-optimized assembly for x86_64, by Diederik Huys).
* Using 10 26-bit limbs (including hand-optimized assembly for 32-bit ARM, by Wladimir J. van der Laan).
Upgrade the vendored libsecp256k1 code `libsecp256k1` v0.2.0 was just released. Update the vendored code using `./vendor-libsecp.sh depend 0_8_0 21ffe4b` ``` git show 21ffe4b commit 21ffe4b22a9683cf24ae0763359e401d1284cc7a (tag: v0.2.0) Merge: 8c949f5 e025ccd Author: Pieter Wuille <pieter@wuille.net> Date: Mon Dec 12 17:00:52 2022 -0500 Merge bitcoin-core/secp256k1#1055: Prepare initial release e025ccdf7473702a76bb13d763dc096548ffefba release: prepare for initial release 0.2.0 (Jonas Nick) 6d1784a2e2c1c5a8d89ffb08a7f76fa15e84fff5 build: add missing files to EXTRA_DIST (Jonas Nick) 13bf1b6b324f2ed1c1fb4c8d17a4febd3556839e changelog: make order of change types match keepachangelog.com (Jonas Nick) b1f992a552785395d2e60b10862626fd11f66f84 doc: improve release process (Jonas Nick) ad39e2dc417f85c1577a6a6a9c519f5c60453def build: change package version to 0.1.0-dev (Jonas Nick) 90618e9263ebc2a0d73d487d6d94fd3af96b973c doc: move CHANGELOG from doc/ to root directory (Jonas Nick) Pull request description: Based on #964 ACKs for top commit: sipa: ACK e025ccdf7473702a76bb13d763dc096548ffefba Tree-SHA512: b9ab71d7362537d383a32b5e321ef44069f00e3e92340375bcd662267bc5a60c2bad60222998e6602cfac24ad65efb23d772eac37c86065036b90ef090b54c49 ``` Requires a new version of `secp256k1-sys`, use v0.8.0 - Update the `secp256k1-sys` manifest (including links field) - Update symbols to use 0_8_0 - Add a changelog entry - depend on the new version in `secp256k1` Which in turn requires a new version of `secp256k1`, use v0.26.0
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* This is an experimental feature that has not received enough scrutiny to satisfy the standard of quality of this library but is made available for testing and review by the community.
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* Scalar operations
* Optimized implementation without data-dependent branches of arithmetic modulo the curve's order.
* Using 4 64-bit limbs (relying on __int128 support in the compiler).
* Using 8 32-bit limbs.
* Modular inverses (both field elements and scalars) based on [safegcd](https://gcd.cr.yp.to/index.html) with some modifications, and a variable-time variant (by Peter Dettman).
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* Group operations
* Point addition formula specifically simplified for the curve equation (y^2 = x^3 + 7).
* Use addition between points in Jacobian and affine coordinates where possible.
* Use a unified addition/doubling formula where necessary to avoid data-dependent branches.
* Point/x comparison without a field inversion by comparison in the Jacobian coordinate space.
* Point multiplication for verification (a*P + b*G).
* Use wNAF notation for point multiplicands.
* Use a much larger window for multiples of G, using precomputed multiples.
* Use Shamir's trick to do the multiplication with the public key and the generator simultaneously.
* Use secp256k1's efficiently-computable endomorphism to split the P multiplicand into 2 half-sized ones.
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* Point multiplication for signing
* Use a precomputed table of multiples of powers of 16 multiplied with the generator, so general multiplication becomes a series of additions.
* Intended to be completely free of timing sidechannels for secret-key operations (on reasonable hardware/toolchains)
* Access the table with branch-free conditional moves so memory access is uniform.
* No data-dependent branches
* Optional runtime blinding which attempts to frustrate differential power analysis.
* The precomputed tables add and eventually subtract points for which no known scalar (secret key) is known, preventing even an attacker with control over the secret key used to control the data internally.
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Build steps
-----------
libsecp256k1 is built using autotools:
$ ./autogen.sh
$ ./configure
$ make
$ make check # run the test suite
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$ sudo make install # optional
Upgrade the vendored libsecp256k1 code `libsecp256k1` v0.2.0 was just released. Update the vendored code using `./vendor-libsecp.sh depend 0_8_0 21ffe4b` ``` git show 21ffe4b commit 21ffe4b22a9683cf24ae0763359e401d1284cc7a (tag: v0.2.0) Merge: 8c949f5 e025ccd Author: Pieter Wuille <pieter@wuille.net> Date: Mon Dec 12 17:00:52 2022 -0500 Merge bitcoin-core/secp256k1#1055: Prepare initial release e025ccdf7473702a76bb13d763dc096548ffefba release: prepare for initial release 0.2.0 (Jonas Nick) 6d1784a2e2c1c5a8d89ffb08a7f76fa15e84fff5 build: add missing files to EXTRA_DIST (Jonas Nick) 13bf1b6b324f2ed1c1fb4c8d17a4febd3556839e changelog: make order of change types match keepachangelog.com (Jonas Nick) b1f992a552785395d2e60b10862626fd11f66f84 doc: improve release process (Jonas Nick) ad39e2dc417f85c1577a6a6a9c519f5c60453def build: change package version to 0.1.0-dev (Jonas Nick) 90618e9263ebc2a0d73d487d6d94fd3af96b973c doc: move CHANGELOG from doc/ to root directory (Jonas Nick) Pull request description: Based on #964 ACKs for top commit: sipa: ACK e025ccdf7473702a76bb13d763dc096548ffefba Tree-SHA512: b9ab71d7362537d383a32b5e321ef44069f00e3e92340375bcd662267bc5a60c2bad60222998e6602cfac24ad65efb23d772eac37c86065036b90ef090b54c49 ``` Requires a new version of `secp256k1-sys`, use v0.8.0 - Update the `secp256k1-sys` manifest (including links field) - Update symbols to use 0_8_0 - Add a changelog entry - depend on the new version in `secp256k1` Which in turn requires a new version of `secp256k1`, use v0.26.0
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To compile optional modules (such as Schnorr signatures), you need to run `./configure` with additional flags (such as `--enable-module-schnorrsig`). Run `./configure --help` to see the full list of available flags.
Usage examples
-----------
Usage examples can be found in the [examples](examples) directory. To compile them you need to configure with `--enable-examples`.
* [ECDSA example](examples/ecdsa.c)
* [Schnorr signatures example](examples/schnorr.c)
* [Deriving a shared secret (ECDH) example](examples/ecdh.c)
To compile the Schnorr signature and ECDH examples, you also need to configure with `--enable-module-schnorrsig` and `--enable-module-ecdh`.
Test coverage
-----------
This library aims to have full coverage of the reachable lines and branches.
To create a test coverage report, configure with `--enable-coverage` (use of GCC is necessary):
$ ./configure --enable-coverage
Run the tests:
$ make check
To create a report, `gcovr` is recommended, as it includes branch coverage reporting:
$ gcovr --exclude 'src/bench*' --print-summary
To create a HTML report with coloured and annotated source code:
$ mkdir -p coverage
$ gcovr --exclude 'src/bench*' --html --html-details -o coverage/coverage.html
Benchmark
------------
If configured with `--enable-benchmark` (which is the default), binaries for benchmarking the libsecp256k1 functions will be present in the root directory after the build.
To print the benchmark result to the command line:
$ ./bench_name
To create a CSV file for the benchmark result :
$ ./bench_name | sed '2d;s/ \{1,\}//g' > bench_name.csv
Reporting a vulnerability
------------
See [SECURITY.md](SECURITY.md)