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Installation

npm install privacycash --save
Requires Node.js 24+. The SDK is written in TypeScript and includes type definitions.

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Deriving Encryption Key

Client need to ask user to sign an offchain message, before the user can interact with Privacy Cash. 
async function getSignedSignature(signed: Signed) {
    if (signed.signature) {
        return
    }
    const encodedMessage = new TextEncoder().encode(`Privacy Money account sign in`)
    const cacheKey = `zkcash-signature-${signed.publicKey.toBase58()}`

    // ask for sign
    let signature: Uint8Array
    try {
        signature = await signed.provider.signMessage(encodedMessage)
    } catch (err: any) {
        if (err instanceof Error && err.message?.toLowerCase().includes('user rejected')) {
            throw new Error('User rejected the signature request')
        }
        throw new Error('Failed to sign message: ' + err.message)
    }
    
    if (currentSigned.pubKeyStr != signed.publicKey.toString()) {
        throw new Error(`Don't switch account when signing in. Refresh the page and try again.`)
    }

    // If wallet.signMessage returned an object, extract `signature`
    // @ts-ignore
    if (signature.signature) {
        // @ts-ignore
        signature = signature.signature
    }

    if (!(signature instanceof Uint8Array)) {
        throw new Error('signature is not an Uint8Array type')
    }
    signed.signature = signature
}

export type Signed = {
    publicKey: PublicKey,
    signature?: Uint8Array,
    provider: any
}
Once the user signed the message, pass the resulting signature to EncryptionService of the SDK: 
export * from "privacycash/utils"

let encryptionService = new EncryptionService();
encryptionService.deriveEncryptionKeyFromSignature(signed.signature);

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Interacting with Privacy Cash

Once above steps are done, client can query balance, make deposits and withdrawals.

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Common Issues

  1. Next.js project needs to update the postinstall build scripts: 
    "scripts": {
    "postinstall": "cp node_modules/@lightprotocol/hasher.rs/dist/hasher_wasm_simd_bg.wasm node_modules/@lightprotocol/hasher.rs/dist/browser-fat/es/ && cp node_modules/@lightprotocol/hasher.rs/dist/light_wasm_hasher_bg.wasm node_modules/@lightprotocol/hasher.rs/dist/browser-fat/es/",
},..}