Does Kaspa's GHOSTDAG protocol have a formal security proof?

Yes — GHOSTDAG's security has been formally proven in a peer-reviewed paper (IACR ePrint 2018/104). A formal security proof means the protocol's safety properties are not just claimed but mathematically demonstrated and independently reviewed by researchers. Because GHOSTDAG is a mathematical generalization of Bitcoin's Nakamoto Consensus, it inherits the same security guarantees that have protected Bitcoin since 2009. For a beginner, this matters because it distinguishes Kaspa from projects whose security rests on informal arguments — GHOSTDAG's guarantees are written in math, not marketing.