the system

Specular is an L2 system designed to scale Ethereum securely, with minimal additional trust assumptions. Specifically, it is an EVM-native optimistic rollup, relying on existing Ethereum infrastructure both to bootstrap protocol security and to enable native compatibility for all existing Ethereum applications & tooling.

the philosophy

Optimistic rollups are generally secure under a 1-of-n honest minority assumption. The plausibility of this assumption, however, rests not only upon the diversity of the validator set, but also upon the diversity of the L2 client software stack that validators are allowed to operate—and as a corollary, the traditionally extensive privileges of client developers. An optimistic rollup protocol should therefore aim to facilitate client diversity in a trust-minimizing and credibly neutral form.

Trust minimization. A bug or exploit in one client software stack (or even several) should have no impact on the system’s overall security. To minimize software trust and provide resiliency against exploits, the security of an optimistic rollup should therefore only depend on the conformance of a single software stack to the L2 protocol specification.

Credible neutrality. The protocol should not be in the position of picking winners and losers by canonicalizing one particular software stack over another within the security mechanism. To maximize credible neutrality at the client development layer, the protocol should therefore enforce minimal constraints over L2 execution semantics (beyond as necessary to guarantee security). This means that a validator should be able to, just as in the case of Ethereum, operate permissionlessly using any client software stack—existing or new—of their choosing.

the protocol

Specular's underlying protocol is therefore designed with these properties in mind. We aim to minimize trust in any one component by enabling opportunistic 1-of-N-version programming across the entire L2 stack. This is achieved primarily through an interactive proof system designed to (1) natively target an abstract EVM-rooted protocol specification—rather than a particular concrete implementation, as is the case in state-of-the-art systems today; and (2) facilitate the application of standard techniques to provide strong formal guarantees of correctness.

references & acknowledgements

An initial manuscript describing Specular in more detail is available here (subject to change).

This work is a product of academic research conducted at RDI (UC Berkeley), and is supported by grants from the Ethereum Foundation and Gnosis.