tiny-secp256k1

This library is under development, and, like the secp256k1 C library (through secp256k1-sys Rust crate) it depends on, this is a research effort to determine an optimal API for end-users of the bitcoinjs ecosystem.

Installation

npm

npm install tiny-secp256k1

yarn

yarn add tiny-secp256k1

WebAssembly and Node.js version

Previous version of tiny-secp256k1 implement C++ addon through NAN (Native Abstractions for Node.js) and elliptic as fallback when addon can not be built or in browser-like environement.

Current version use Rust crate (which use C library) compiled to WebAssembly. With Wasm same code executed in any environment. Wasm is faster than elliptic but slower than node bindings (results in PR or you can run own benchmark in benches directory).

Tools like webpack, environments like React Native, and a large part of the JavaScript/TypeScript ecosystem has support for WASM based libraries. However, it usually involves special config settings which might be difficult to figure out. We have examples in the examples folder that uses webpack to create a demo website.

However, there are also alternative implementations of the interface of this library.

Alternatives

1. @bitcoinjs-lib/tiny-secp256k1-asmjs - This library uses wasm2js to convert this library into pure JS. It is about 10x ~ 20x slower than WASM and 3x ~ 10x slower than our old v1 JS implementation.
2. @bitcoinerlab/secp256k1 - This library uses noble/secp256k1, and therefore it uses JS native BigInt. If you can support BigInt it is much faster than ASM.JS, however, this is not maintained by this library's maintainers, so there's no guarantee that they will keep up with any interface changes in the future. Please check before using. It is about 1.5x ~ 5x slower than WASM.

Building

For building locally you need C/C++ toolchain, Rust version >=1.50.0 and wasm-opt from binaryen.

rustup is a recommended way to install Rust. You also will need wasm32-unknown-unknown target.

rustup toolchain install stable --target wasm32-unknown-unknown --component clippy --component rustfmt

After installing development dependencies with npm you can build Wasm:

make build-wasm

or run tests:

make test

Alternative way is to use Docker:

% docker build -t tiny-secp256k1 .
% docker run -it --rm -v `pwd`:/tiny-secp256k1 -w /tiny-secp256k1 tiny-secp256k1
# make build

Examples

tiny-secp256k1 includes two examples. First is simple script for Node.js which generate random data and print arguments and methods results. Second is React app.

React app is builded in GitHub Actions on each commit to master branch and uploaded to gh-pages branch, which is always available online: https://bitcoinjs.github.io/tiny-secp256k1/

Documentation

isPoint (A)

isPoint :: Buffer -> Bool

Returns false if

• A is not encoded with a sequence tag of 0x02, 0x03 or 0x04
• A.x is not in [1...p - 1]
• A.y is not in [1...p - 1]

isPointCompressed (A)

isPointCompressed :: Buffer -> Bool

Returns false if the pubkey is not compressed.

isXOnlyPoint (A)

isXOnlyPoint :: Buffer -> Bool

Returns false if the pubkey is not an xOnlyPubkey.

isPrivate (d)

isPrivate :: Buffer -> Bool

Returns false if

• d is not 256-bit, or
• d is not in [1..order - 1]

pointAdd (A, B[, compressed])

pointAdd :: Buffer -> Buffer [-> Bool] -> Maybe Buffer

Returns null if result is at infinity.

Throws:

• Expected Point if !isPoint(A)
• Expected Point if !isPoint(B)

pointAddScalar (A, tweak[, compressed])

pointAddScalar :: Buffer -> Buffer [-> Bool] -> Maybe Buffer

Returns null if result is at infinity.

Throws:

• Expected Point if !isPoint(A)
• Expected Tweak if tweak is not in [0...order - 1]

pointCompress (A, compressed)

pointCompress :: Buffer -> Bool -> Buffer

Throws:

• Expected Point if !isPoint(A)

pointFromScalar (d[, compressed])

pointFromScalar :: Buffer [-> Bool] -> Maybe Buffer

Returns null if result is at infinity.

Throws:

• Expected Private if !isPrivate(d)

xOnlyPointFromScalar (d)

xOnlyPointFromScalar :: Buffer -> Buffer

Returns the xOnlyPubkey for a given private key

Throws:

• Expected Private if !isPrivate(d)

xOnlyPointFromPoint (p)

xOnlyPointFromPoint :: Buffer -> Buffer

Returns the xOnlyPubkey for a given DER public key

Throws:

• Expected Point if !isPoint(p)

pointMultiply (A, tweak[, compressed])

pointMultiply :: Buffer -> Buffer [-> Bool] -> Maybe Buffer

Returns null if result is at infinity.

Throws:

• Expected Point if !isPoint(A)
• Expected Tweak if tweak is not in [0...order - 1]

privateAdd (d, tweak)

privateAdd :: Buffer -> Buffer -> Maybe Buffer

Returns null if result is equal to 0.

Throws:

• Expected Private if !isPrivate(d)
• Expected Tweak if tweak is not in [0...order - 1]

privateSub (d, tweak)

privateSub :: Buffer -> Buffer -> Maybe Buffer

Returns null if result is equal to 0.

Throws:

• Expected Private if !isPrivate(d)
• Expected Tweak if tweak is not in [0...order - 1]

privateNegate (d)

privateNegate :: Buffer -> Buffer

Returns the negation of d on the order n (n - d)

Throws:

• Expected Private if !isPrivate(d)

xOnlyPointAddTweak (p, tweak)

xOnlyPointAddTweak :: Buffer -> Buffer -> { parity: 1 | 0; xOnlyPubkey: Buffer; }

Returns the tweaked xOnlyPubkey along with the parity bit (number type of 1|0)

Throws:

• Expected Point if !isXOnlyPoint(p)
• Expected Tweak if !isXOnlyPoint(tweak)

xOnlyPointAddTweakCheck (p1, p2, tweak[, tweakParity])

xOnlyPointAddTweakCheck :: Buffer -> Buffer -> Buffer [-> 1 | 0] -> Bool

Checks the tweaked pubkey (p2) against the original pubkey (p1) and tweak. This is slightly slower if you include tweakParity, tweakParity will make it faster for aggregation later on.

Throws:

• Expected Point if !isXOnlyPoint(p1)
• Expected Point if !isXOnlyPoint(p2)
• Expected Tweak if !isXOnlyPoint(tweak)
• Expected Parity if tweakParity is not 1 or 0

sign (h, d[, e])

sign :: Buffer -> Buffer [-> Buffer] -> Buffer

Returns normalized signatures, each of (r, s) values are guaranteed to less than order / 2. Uses RFC6979. Adds e as Added Entropy to the deterministic k generation.

Throws:

• Expected Private if !isPrivate(d)
• Expected Scalar if h is not 256-bit
• Expected Extra Data (32 bytes) if e is not 256-bit

signRecoverable (h, d[, e])

signRecoverable :: Buffer -> Buffer [-> Buffer] -> { recoveryId: 0 | 1 | 2 | 3; signature: Buffer; }

Returns normalized signatures and recovery Id, each of (r, s) values are guaranteed to less than order / 2. Uses RFC6979. Adds e as Added Entropy to the deterministic k generation.

Throws:

• Expected Private if !isPrivate(d)
• Expected Scalar if h is not 256-bit
• Expected Extra Data (32 bytes) if e is not 256-bit

signSchnorr (h, d[, e])

signSchnorr :: Buffer -> Buffer [-> Buffer] -> Buffer

Returns normalized schnorr signature. Uses BIP340 nonce generation. Adds e as Added Entropy.

Throws:

• Expected Private if !isPrivate(d)
• Expected Scalar if h is not 256-bit
• Expected Extra Data (32 bytes) if e is not 256-bit

verify (h, Q, signature[, strict = false])

verify :: Buffer -> Buffer -> Buffer [-> Bool] -> Bool

Returns false if any of (r, s) values are equal to 0, or if the signature is rejected.

If strict is true, valid signatures with any of (r, s) values greater than order / 2 are rejected.

Throws:

• Expected Point if !isPoint(Q)
• Expected Signature if signature has any (r, s) values not in range [0...order - 1]
• Expected Scalar if h is not 256-bit

recover (h, signature, recoveryId[, compressed = false])

verify :: Buffer -> Buffer -> Number [-> Bool] -> Maybe Buffer

Returns the ECDSA public key from a signature if it can be recovered, null otherwise.

Throws:

• Expected Signature if signature has any (r, s) values not in range (0...order - 1]
• Bad Recovery Id if recid & 2 !== 0 and signature has any r value not in range (0...P - N - 1]
• Expected Hash if h is not 256-bit

verifySchnorr (h, Q, signature)

verifySchnorr :: Buffer -> Buffer -> Buffer -> Bool

Returns false if any of (r, s) values are equal to 0, or if the signature is rejected.

Throws:

• Expected Point if !isPoint(Q)
• Expected Signature if signature has any (r, s) values not in range [0...order - 1]
• Expected Scalar if h is not 256-bit

Credit

This library uses the native library secp256k1 by the bitcoin-core developers through Rust crate secp256k1-sys, including derivatives of its tests and test vectors.

LICENSE MIT