How ERC721 Enumerable Works An Enumerable ERC721 is an ERC721 with added functionality that enables a smart contract to list all the NFTs an address owns. This article describes how ERC721Enumerable functions and how we can integrate it into an existing ERC721 project. We’ll use Open Zeppelin’s popular implementation of ERC721Enumerable for our explanation. Prerequisites […]
Checklist for Technical Writing Fluff Are fluff transitions removed? (” It is important to note,” Why did they do this?”, “Here’s how we can solve this problem.”) Sometimes, they are necessary for flow, but most can be removed. “It is important to note” is the most overused phrase in technical writing. Don’t use it. If […]
Hacking Underconstrained Circom Circuits With Fake Proofs The <-- operator in Circom can be dangerous because it assigns values to signals but does not constrain them. But how do you actually exploit write a POC (proof of concept) for this vulnerability? We will be hacking the following circuit: pragma circom 2.1.8; template Mul3() { signal […]
Modifying accounts using different signers In our Solana tutorials thus far, we’ve only had one account initialize and write to the account. In practice, this is very restrictive. For example, if user Alice is transferring points to Bob, Alice must be able to write to an account initialized by user Bob. In this tutorial we […]
Deleting and Closing Accounts and Programs in Solana In the Anchor framework for Solana, close is the opposite of init (initializing an account in Anchor) — it reduces the lamport balance to zero, sending the lamports to a target address, and changes the owner of the account to be the system program. Here is an […]
PDA (Program Derived Address) vs Keypair Account in Solana A program derived address (PDA) is an account whose address is derived from the address of the program that created it and the seeds passed in to the init transaction. Up until this point, we’ve only used PDAs. It is also possible to create an account […]
Owner vs Authority in Solana Newcomers to Solana are frequently confused by the distinction between an “owner” and an “authority.” This article attempts to clear up the confusion as succinctly as possible. Owner vs Authority Only programs can write data to accounts — specifically, only to accounts they own. A program cannot write data to […]
Multicall in Solana: Batching Transactions and Transaction Size Limit Solana has multicall built in In Ethereum, we use the multicall pattern if we want to batch multiple transactions together atomically. If one fails, the rest fails. Solana has this built into the runtime, so we don’t need to implement a multicall. In the example below, […]
Init_if_needed in Anchor and the Reinitialization Attack In previous tutorials, we’ve had to initialize an account in a separate transaction before we can write data to it. We may wish to be able to initialize an account and write data to it in one transaction to simplify things for the user. Anchor provides a handy […]