This is extremely easy, without this we cannot verify the authenticity of keys. In the Steem blockchain, a private key is converted into a public key using Elliptic Curve Cryptography (ECC) on the secp256k1 curve. The private key is used to generate a point on this curve, which forms the public key. This public key is then compressed and encoded using Base58Check, a format that makes it shorter, human-readable, and includes error detection. The final public key starts with the prefix STM, allowing you to prove ownership without exposing the private key itself.

const steem = require('steem');

const privateKey = 'YOUR_WIF_KEY';

const publicKey = steem.auth.wifToPublic(privateKey);

console.log('Public Key:', publicKey);

Above code will print you public key for any given private key