Transient Quantum Resistance, with Application to Ethereum Consensus

We introduce transient quantum resistance, an approach enabling pre-quantum cryptographic primitives to remain secure beyond the quantum computing era in scenarios requiring only temporary forgery prevention. The method binds temporary keys to permanent post-quantum identities within defined timeframes. Applied to Ethereum’s consensus layer, we propose preserving BLS signatures with aggregation capabilities while maintaining a single ~96-byte BLS signature — about three orders of magnitude smaller than alternative quantum-resistant methods. Security relies on the hardness of a modified Diffie-Hellman problem for the duration of an Ethereum epoch.