Hi, to respond to your questions:
We have a mix of public and private servers in Europe. Our platform does not run on top of a blockchain, we leverage on the blockchain using IPFS and Smart Contract for our identity service using the Binance Smart Chain. FortKnoxster is not the average message/calling app, we guarantee the privacy of our users by applying zero knowledge technology in addition to our encryption at transit and at rest. You can find more information about our security on our security page.