@cardinal-cryptography/shielder-sdk-crypto v0.2.0-beta.4

shielder-sdk-crypto

Core cryptographic module for the Shielder SDK, defining the lower-level cryptography interface used for private transactions on the Shielder Network.

Overview

This package provides the foundational cryptographic interfaces and types required by the Shielder protocol, including:

• Field element representation
• Zero-knowledge proofs (ZKP)
• Hashing functions
• Secret derivation

The module defines interfaces that are implemented by platform-specific packages (such as shielder-sdk-crypto-wasm), allowing the main SDK to work across different environments.

Core Components

Field Element Representation

The module provides a Scalar class for representing field elements in the BN256 curve:

import { Scalar } from "@cardinal-cryptography/shielder-sdk-crypto";

// Create a scalar from a bigint
const scalar = Scalar.fromBigint(42n);

// Create a scalar from an Ethereum address
const addressScalar = Scalar.fromAddress(
  "0x7FfA893F1671600ec9b09542B5a432593720B3ee"
);

// Convert scalar back to bigint
const value = scalarToBigint(scalar);

// Compare scalars
const areEqual = scalarsEqual(scalar1, scalar2);

Zero-Knowledge Proofs

The module defines interfaces for generating and verifying zero-knowledge proofs for key operations in the Shielder protocol:

• NewAccountCircuit: For creating new private accounts
• DepositCircuit: For depositing tokens into private accounts
• WithdrawCircuit: For withdrawing tokens from private accounts

Each circuit interface provides methods for:

• Generating proofs
• Computing public inputs
• Verifying proofs

Hashing Functions

The Hasher interface provides cryptographic hashing functionality for Poseidon2 function:

// Poseidon2 hash of multiple scalar inputs
const hash = await cryptoClient.hasher.poseidonHash([scalar1, scalar2]);

// Get the maximum number of inputs supported
const rate = await cryptoClient.hasher.poseidonRate();

Secret Derivation

The SecretManager interface handles the derivation of secrets for private transactions:

// Derive account ID from private key, chain ID, and account nonce
const id = await cryptoClient.secretManager.deriveId(
  "0xprivatekey",
  1n, // chain ID
  0 // account nonce
);

// Get secrets (nullifier) for a specific account and nonce
const { nullifier } = await cryptoClient.secretManager.getSecrets(id, nonce);

Implementations

The interfaces defined in this package are implemented by:

• WebAssembly Implementation (@cardinal-cryptography/shielder-sdk-crypto-wasm)