Before You Paste That Wallet Address: Sanity-Checking Crypto Addresses in Python
Every crypto transfer ends with the same scary moment: you paste a long string into a "recipient" box and press send. There's no chargeback and no support line that can reverse it. If the string is wrong, or right but on the wrong network, the money is usually gone. As developers we can make that moment a lot less scary. This post walks through what a wallet address actually is and a few cheap…
Transferring cryptocurrency involves a final, critical step: entering the recipient's address into the designated field and confirming the transaction. There is no recourse if an error is made, as the funds are irretrievable. Developers can alleviate the anxiety associated with this moment by implementing simple validation checks in their code.
A wallet address is a public identifier that allows coins to be received. It is at the end of a one-way chain, with the private key being a secret number that signs transactions. The public key is derived from the private key and is used by the network to confirm signatures. The address is a condensed encoding, typically a hash of the public key, designed for sharing. Since each step only works in one direction, sharing the address is secure, but sharing the private key or seed phrase is not.
Several formats exist for wallet addresses, each associated with a specific blockchain and incorporating a checksum to help detect errors before the transaction is broadcast to the network. For instance, Bitcoin addresses follow a Bech32 or Base58Check encoding and include a checksum, while Ethereum addresses use an EIP-55 encoding with mixed-case letters.
Ethereum addresses have a built-in checksum in the capitalization of their letters, which can be validated using a simple function in Python that checks for proper format and encoding.
However, a checksum only verifies the integrity of the address and not the network it belongs to. Sending assets on one blockchain to an address intended for another can result in the loss of funds. Therefore, it is essential to specify the network explicitly when sending cryptocurrencies. Additionally, hardware wallets offer an extra layer of security by allowing users to confirm the receiving address directly on the device itself.
Before sending larger amounts, it is advisable to perform test transactions on new routes and pay close attention to any small transfers sent from look-alike addresses, known as address poisoning scams. Privacy considerations are also crucial, as public addresses can reveal transaction histories, making it important to use an address book or allowlist to avoid accidentally sending funds to the wrong destination.
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