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Confidential Assets SDK

WASM Dependencies

This package uses a unified WebAssembly module for cryptographic operations:

  • Discrete log solver: TBSGS-k32 algorithm for decryption (~512 KiB table)
  • Range proofs: Bulletproofs for range proof generation/verification

How WASM Loading Works

The WASM binary is not bundled with the SDK. Instead, it is loaded dynamically at runtime when needed. This is intentional:

Why not bundle the WASM?

  • The .wasm binary is large (~774 KiB for the unified module)
  • Bundling would bloat every app using the SDK, even if they never use confidential assets
  • WASM binaries don't tree-shake - you'd pay the full size cost even if the feature is unused

What the npm dependency provides:

  • TypeScript type definitions
  • JavaScript glue code (thin wrappers that call into WASM)
  • These are small and get bundled normally with the SDK

What gets loaded at runtime:

  • The actual .wasm binary file
  • Loaded via fetch() + WebAssembly.instantiate() only when initializeWasm(), initializeSolver(), or range proof functions are called
  • Single initialization: Both discrete log and range proof functionality share the same WASM module, so it only needs to be loaded once

Environment-specific loading:

In browser environments, WASM is fetched from unpkg.com CDN.

In Node.js environments (e.g., running tests), the code automatically detects Node.js and loads WASM from local node_modules. This avoids network requests and ensures tests work offline.

WASM Initialization

The SDK provides unified WASM initialization:

import { initializeWasm, isWasmInitialized } from "@aptos-labs/confidential-asset";

// Initialize once - shared between discrete log and range proofs
await initializeWasm();

// Check if initialized
if (isWasmInitialized()) {
  // Both discrete log and range proof functions are ready
}

For convenience, the SDK auto-initializes when you call any function that needs WASM. Manual initialization is only needed if you want to control when the WASM download happens.

Setting Up Local WASM for Development

If you want to use locally-built WASM bindings (e.g., for development or testing changes):

  1. Clone and build the WASM bindings:

    cd ~/repos
git clone https://github.com/aptos-labs/confidential-asset-wasm-bindings
cd confidential-asset-wasm-bindings
./scripts/build-all.sh

  2. Update package.json to use the local path:

    "@aptos-labs/confidential-asset-wasm-bindings": "file:../../confidential-asset-wasm-bindings/aptos-confidential-asset-wasm-bindings"

  3. Install dependencies:

    # Use --force if you've made some local changes to the DL algorithm; otherwise the version remains the same and this does nothing
pnpm install

Now tests will use your locally-built WASM.

Testing

To test against a modified aptos-core repo:

First, run a local node from your modified aptos-core branch. (You may need to delete ~/.aptos/testnet or else it will error. Proceed with caution; not sure what sensitive stuff you may have there.)

ulimit -n unlimited
cargo run -p aptos -- node run-localnet --with-indexer-api --test-dir=~/.aptos/testnet --assume-yes --force-restart

Second, run the SDK test of your choosing; e.g.:

pnpm test tests/e2e/confidentialAsset.test.mts

pnpm test tests/e2e/

pnpm test decryption

pnpm test tests/e2e/confidentialAsset.test.mts -t "rotate Alice" --runInBand

Or, run all tests:

pnpm test

Useful tests to know about

Discrete log / decryption benchmarks

SKIP_SETUP=1 pnpm test discrete

Range proof tests

pnpm test tests/units/confidentialProofs.test.mts