Zero-knowledge proofs and fully homomorphic encryption are promising privacy solutions, but they're facing real engineering hurdles. With ZK systems, the bottleneck comes down to prover efficiency—generating proofs is computationally heavy. Meanwhile, verification costs need to stay competitive. The crypto space is actively tackling this through recursive proof approaches and hardware acceleration breakthroughs. FHE has its own challenge: encrypted computation gets slower as noise accumulates in the ciphertexts, plus managing encryption keys securely at scale remains tricky. Both technologies are maturing fast, but cracking these efficiency problems is critical before mainstream adoption becomes realistic.