Ethereum: Recovering the public key from a transaction

Decoding the Public Key: Understanding Ethereum Transactions

In the vast and complex world of cryptocurrencies, retrieving a recipient’s public key can be a challenge. This article will delve into the concept of recovering a public key from an Ethereum transaction and provide insights on whether it is possible to obtain this information.

What is a Transaction?

A transaction on the Ethereum network is a message sent by one user to another. It contains data such as sender’s public key, receiver’s public key, and the amount of Ether (ETH) being transferred. The transaction is verified by the Ethereum network using complex cryptographic algorithms, ensuring its integrity.

How Does a Transaction Identify a Public Key?

A transaction typically includes fields that identify its owner (sender), including their public key. However, these fields are not directly linked to the public key itself; they merely contain references to it for verification purposes. For example, in the Ethereum blockchain’s tx data structure, you’ll find a field called “from” which contains the sender’s public key.

Recovering the Public Key from a Transaction

To recover the recipient’s public key from an Ethereum transaction, we need to understand how the network identifies and verifies transactions. Here are the general steps:

• Transaction ID: Each transaction has a unique identifier (TXID) assigned by the Ethereum network. This TXID contains information about the transaction, including its sender and receiver.

• From field: As mentioned earlier, the from field in the transaction data structure contains the sender’s public key. However, this field is not directly linked to the recipient’s public key.

• Recipient’s signature: To verify a transaction, the network checks if it has been signed by the intended recipient (the person whose Ethereum balance the transaction was sent from). The recipient’s signature ensures that the transaction was indeed intended for them.

Can We Get the Public Key of a User?

Now, let’s address your question: is it possible to get the public key of a user if we have a transaction from that user in our wallet?

Unfortunately, no. In Ethereum, once a transaction has been sent and verified by the network, its sender’s public key cannot be retrieved or obtained directly. The sender’s public key is only available to verify the transaction, not to obtain it.

The from field contains the sender’s public key, but this information is intended for verification purposes only and does not provide access to the sender’s personal data, such as their public key.

Conclusion

While retrieving a recipient’s public key from an Ethereum transaction can be challenging due to its role in verifying transactions, it is not possible to obtain this information directly. The from field contains references to the sender’s public key for verification purposes only.

However, if you need to verify a transaction or send/receive funds, there are other methods available that do not require access to the recipient’s private keys or public keys. These include using the Ethereum Wallet app (if you’re on a mobile device) or interacting with third-party services that support secure and private transactions.