Public key cryptography uses a pair: one secret, one shareable. The public key can be published freely; deriving the private-key from it is computationally infeasible with current technology.
Chains usually hash the public key to produce a shorter crypto-address, which is what you hand out to receive funds. Verifiers use the public key to confirm a signature really came from the key holder.
The commonly cited quantum-computing concern targets exactly this step. It is a long-horizon research risk rather than a present trading risk, and chains have credible migration paths, but it is honest to say the assumption is "infeasible today", not "impossible forever".
Related: private-key, crypto-address, cryptographic-hash, seed-phrase