CODEWITHSUNDEEP
blockchainweb3jsethers.js
Stuart
Stuart

Reputation: 6780

How to create a transaction using web3 or ethers.js without setting private_key

What i am trying to do:

Building a small app that allows a user to purchase a service for a set amount of tokens. For example, 100 tokens for service A, 500 tokens for service B. This will be for a custom token on the harmony blockchain.

What i know: I already know how to connect to metamask and get the users address. Signer and provider are available to me.

What confuses me: Examples and documentation all refer to a private_key and creating a wallet, i don't need to do that, i need to use the users existing wallet.

What i need to do:

  1. Prompt a transaction in the user wallet (harmony one or metamask) for a set amount of tokens.

  2. Check if the user has required balance (seems trivial knowing i can read their balance).

  3. Make the transaction. Also seems ok after reading the docs.

  4. Get a receipt, then call a callback/my code. Again, seems ok after reading the docs.

All pretty straight forward, but again - every document i read always refers to setting a private key - surely i don't need to do this?

Upvotes: 1

Views: 2805

Answers (1)

Petr Hejda
Petr Hejda

Reputation: 43581

A transaction always needs to be signed by a private key generating the sender address. Otherwise it's rejected by the network.

Examples and documentation all refer to a private_key and creating a wallet, i don't need to do that, i need to use the users existing wallet.

every document i read always refers to setting a private key - surely i don't need to do this?

A backend approach is to import the private key to the app and use it to sign the transaction.

However, there's also a frontend approach: Send a request to a wallet browser extension to sign the transaction and broadcast it to the network. The wallet extension then pops up a window and lets the user chose whether they want to sign the transaction (with their private key, not shared with the app) and broadcast it - or not.

You can find an example of such request in the MetaMask docs page.

An advantage of this approach is that your app doesn't need to ask for the user's private key. A disadvantage is that if the user haven't installed a browser wallet compatible with your app, they can't send the transaction (or at least not so easily).

Note: I'm not familiar with the Harmony wallet, but I'm assuming it works in a similar way as MetaMask - because Harmony is an EVM-compatible network, and MetaMask only supports EVM-compatible networks.

Upvotes: 2

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