@hathor/ct-crypto-wasm

Browser-compatible (wasm-bindgen) build of the Hathor confidential-transaction crypto primitives.

This crate is the verifier-only sibling of @hathor/ct-crypto-node:

• ✅ deriveAssetTag, deriveTag, htrAssetTag
• ✅ createAssetCommitment (blinded asset generator for FullShielded)
• ✅ createCommitment (Pedersen value commitment)
• ✅ createTrivialCommitment

Range-proof rewind, ECDH and surjection-proof creation are not exposed — anyone holding the cleartext value / vbf / abf already has the rewound output, so those primitives would only inflate the WASM artifact for browser consumers.

The Node-side @hathor/ct-crypto-node package keeps the full surface for wallet-lib's signing / scanning paths.

Build

The crate is consumed via npm (npm install @hathor/ct-crypto-wasm); to build the artifact yourself you need:

• Rust with the wasm32-unknown-unknown target
• An unwrapped clang with the wasm32 backend (nix's wrapped clang injects host-only flags; emscripten's emcc rejects bare wasm32)
• wasm-pack

The repo ships a flake that wires all three:

nix develop --command ./scripts/build-wasm.sh

That produces a publishable artifact at pkg/. To publish:

cd pkg && npm publish --access public

Tests

cargo test                              # native unit tests (generators, pedersen)
nix develop --command wasm-pack test --node   # wasm bindings (optional)

Layout

src/
  lib.rs           # exports + module gate
  error.rs         # HathorCtError
  types.rs         # TokenUid, COMMITMENT_SIZE, GENERATOR_SIZE
  generators.rs    # asset-tag derivation + asset-commitment construction
  pedersen.rs      # Pedersen commitment math
  wasm_bindings.rs # wasm-bindgen surface
flake.nix          # dev shell (wasm-pack + clang-unwrapped + llvm-ar)
scripts/build-wasm.sh   # builds + patches pkg/package.json with the npm-scoped name

The crypto core (generators.rs, pedersen.rs) is duplicated from the sibling hathor-ct-crypto repo so the WASM crate publishes, audits and builds independently. Behavioral parity with the NAPI bindings is enforced by wallet-lib's __tests__/shielded/provider.test.ts round-trip suite.