Ethereum: Why do keys need both X and Y coordinates, if X can be solved for Y using the curve equation?

Understanding Ethereum Private Keys: The Role of X and Y Coordinates

The Ethereum blockchain, like other cryptocurrencies, uses public-key cryptography to secure transactions and control access to funds. A key aspect of this system is the private key, which allows users to manage their funds. However, you may wonder why both X and Y coordinates are used in the Ethereum private key generation process. In this article, we will delve into the rationale behind the use of X and Y coordinates and explore how they contribute to Ethereum’s security and efficiency.

The Importance of Public and Private Key Pairing

Ethereum’s public-key cryptography relies on a secure key pair: a public key (or address) and a private key. The public key is used to broadcast transactions, while the private key is used to sign transactions. However, if either component were compromised, the entire system would be compromised.

The Challenge of Solving X for Y

One of the limitations of the Diffie-Hellman Key Exchange (DHKE) algorithm, which is widely used in Ethereum’s private key generation process, is its ability to solve X from Y. This is called the “diffusion problem.” DHKE uses a mathematical formula to derive X from Y, but it cannot guarantee that X will always be unique. In other words, there are multiple possible values ​​of Y that can lead to the same value of X.

Why Both X and Y Are Necessary

To solve this problem, Ethereum developers introduced the concept of both X and Y coordinates into their public key cryptography. The idea is that a private key consists of two separate components: a 256-bit number (X) and another 256-bit number (Y). The relationship between these two numbers is determined by the equation of a curve used to generate the private key.

Curve Equation

The curve equation used in the Ethereum private key generation process is derived from the elliptic curve cryptography (ECC) algorithm originally developed for RSA. ECC generates a pair of large numbers (X and Y) such that the modulus of their product, N, is equal to 1, where N is the modulus.

How ​​the X and Y coordinates work together

To understand how the X and Y coordinates work together in the Ethereum private key generation process, let’s take a closer look at the curve equation:

Y = k^X mod n

where “k” is an integer, “X” is a 256-bit number from the Diffie-Hellman key exchange algorithm, and “n” is the modulus of the elliptic curve. The relationship between X and Y can be visualized using a diagram, such as the one provided by Bitcoin.org (

Why are both X and Y needed

The combination of X and Y coordinates in the Ethereum private key generation process serves several purposes:

  • Security: Using both X and Y coordinates ensures that the private key is secure against attacks, even if any component is compromised.
  • Efficiency: By using a single curve equation, the development team has made it possible to generate multiple private keys with unique values ​​for each component (X and Y), reducing the risk of collisions between different pairs.
  • Efficient key generation: Using both X and Y coordinates ensures efficient key generation, which is crucial for the operation of the Ethereum network.

Conclusion

Ethereum: Why do keys need both X and Y coordinates, if X can be solved for Y using the curve equation?

In conclusion, using both X and Y coordinates in the Ethereum private key generation process provides an additional level of security and efficiency. By combining these two components, developers have been able to create a robust public-key cryptography system that can withstand various types of attacks while being efficient enough for real-world applications.


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