The best way to reach me for professional reasons is to send an email to Stefan.Dziembowski@crypto.edu.pl.
Please avoid calling my phone on non-urgent matters.
Also, please refrain from texting my phone, sending messages via apps such as Signal, Telegram, WhatsApp, etc., or social media messengers (LinkedIn, Facebook, Twitter, etc.). I may not notice them, and even if I do, I may easily forget to reply to them (sorry!). Email is the only channel of communication that I regularly check and where I put a vacation responder when I am away.
I generally do not respond to messages from publishers known for sending spam (such as MDPI). I also ignore review requests if they concern papers that are clearly out of the scope of my research interest.