Starknet relies on Ethereum for bridge messaging and blob data availability using KZG commitments and elliptic-curve cryptography, which StarkWare identified as post-quantum vulnerabilities that cannot upgrade independently while remaining a Layer 2.

From the articleStarknet Moves Toward Post-Quantum Layer 1 as Voters Back Ethereum SplitAlso in Starknet community overwhelmingly backs research into becoming an independent post-quantum Layer 1, Starknet Voters Back Post-Quantum L1 Research, Starknet Opens Layer 1 Research After 93.5% Poll Vote, Targets Quantum Safety by 2027 - Unchained, Starknet Voters Back Post-Quantum L1 Research, Starknet's proposed Ethereum exit wins 93.52% support for further research, Starknet Votes to Explore Going Solo as a Post-Quantum L1