Vol. I  ·  No. CCXIV  ·  MMXXVI

The Compendium of Layer the Second Being a Treatise upon the Mechanisms by Which the Ethereum Engine is Made to Bear an Increase of Traffic, with Engravings & Annotations

Published at the Sign of the Brass Burin  ·  layer2.wiki
❦ Editors’ Dispatch ❦

On the Necessity of Layer the Second, with Some Observations upon Its Several Forms

“The Engine, being prodigious in its labours, must yet be relieved of the more trivial computations, lest the whole of Christendom await the settling of a single farthing’s transfer.”

THE GREAT ENGINE

Fig. II. — The Great Engine of Settlement, with its Auxiliary Cogs, signifying the principal Layer alongside its Subordinate Mechanisms.

When, in the autumn of the year 2015, the Ethereum Engine was first set into motion, its inventors did remark with no small satisfaction upon the universality of its computation. Yet within five short years it became apparent — as it had been, in earlier ages, with the canals of Manchester and the rookeries of London — that any artery of commerce, however nobly conceived, must in the end suffer the indignities of congestion.

The mechanisms presently described — rollups, state channels, sidechain bridges, and the systems of data availability — have arisen as auxiliary engines, not unlike the donkey-engines that assist the larger steam plant of a great mill. They preserve the dignity of the principal Engine while offering passage to the multitude.

The reader is invited to peruse the entries which follow, each being a treatise upon a particular contrivance, illustrated after the manner of the better engineering periodicals.

Vol. I · Entry the First · Of Mechanisms Cryptographic

Of Rollups, both Optimistick & Zero-Knowing

A rollup is a contrivance whereby a great quantity of transactions, performed elsewhere, are gathered into a single parcel and presented to the principal Engine for its sanction. The principal Engine, being relieved of the labour of computing each transaction in turn, has merely to verify the parcel as a whole — a saving of effort which the careful Reader will at once perceive to be of the greatest moment.

Two species are commonly distinguished. The Optimistick rollup proceeds upon the assumption that the parcel is honest, and offers a window of seven days during which any vigilant party may submit a fraud-proof in objection. The Zero-Knowing rollup, by contrast, accompanies its parcel with a cryptographic certificate of correctness, called a validity-proof, which the Engine may verify in a single brief computation.

The mechanical metaphor is plain: an escapement, in a Victorian chronometer, releases the mainspring's tension by precise increments. So too does a rollup release the burden of computation by precise, sanctioned bundles, returning at last to settle accounts with the great mainspring of consensus.

Definition.

Rollup. — An auxiliary engine which performs computations off the principal chain and submits a periodic settlement, attested by either economic incentive (Optimistick) or mathematical proof (Zero-Knowing).

a. The Rollup-Wheel b. The Auxiliary Cog c. The Mainspring FIG. III
Fig. III. — The principal mechanism of an Optimistick Rollup, showing (a) the rollup-wheel of bundled transactions, (b) the auxiliary cog of the sequencer, and (c) the mainspring providing security from Layer the First.

Vol. I · Entry the Second · Of Conduits Pneumatick

Of State Channels, & their Brass Conduits

L1 SETTLEMENT L1 SETTLEMENT pressure of state FIG. IV Pneumatic conduit between two settlement-houses
Fig. IV. — A state channel, after the manner of a pneumatic dispatch tube, by which capsules of state pass between two settlement-houses without disturbing the principal Engine.

A state channel is, in essence, a private conduit, opened between two parties by the lodgement of a deposit upon the principal chain, and closed by the joint signature of a final account. Between the opening and the closing, the parties may exchange any number of intermediate states, each signed by both, — and none of these intermediate states need ever trouble the Engine.

The Reader is invited to picture, in the great Crystal Palace of finance, two adjoining counting-houses connected by a brass pneumatic tube. Capsules pass to and fro at the speed of sound, each containing a small bill of exchange, — and only at the close of business is a single, summary account dispatched to the central Bank.

  • ❦ The conduit must first be opened, by lodgement upon the chain.
  • ❦ Any number of states may pass within, — the more, the greater the economy.
  • ❦ The conduit is at length closed, & only the final account settled.
  • ❦ Should one party prove dishonest, the Engine adjudicates by the most recent signed state.

Such conduits are admirably suited to repeated commerce between known parties, — as between gaming houses, payment processors, and the more frequent customers of an exchange.

Vol. I · Entry the Third · Of Spans & Crossings

Of Sidechain Bridges, spanning the Consensus Gap

Where a sidechain has been erected upon its own consensus, — possessed of its own validators, its own block-times, and its own tariffs of gas, — the question naturally arises: by what means shall a token, residing upon the principal chain, find passage to the sidechain, and thence return?

The answer is the bridge: a contrivance of two trustees, posted upon either bank of the “Consensus Gap,” who confer upon one another the necessary attestations. Tokens are locked upon the principal chain, and minted in equivalent quantity upon the sidechain. To return, they are burnt upon the sidechain, and released upon the principal chain.

Caution.

The integrity of any bridge is determined by the integrity of its trustees. The Reader is solemnly enjoined to inquire, before any crossing, into the character & constitution of the validating parties, — for the river is deep, & the current swift.

The most considered designs employ neither a single trustee nor a fixed committee, but a light-client bridge, — in which each chain verifies the headers of the other by cryptographic means. Such a bridge requires no trust beyond the consensus rules themselves, & is the natural successor to the elder forms.

L1 toll L2 toll ~ The Consensus Gap ~ FIG. V
Fig. V. — A suspension bridge of the wrought-iron lattice form, spanning the Consensus Gap, with toll-houses (validators) at either bank, and a carriage (token transfer) mid-passage.

Vol. I · Entry the Fourth · Of Repositories & Catalogues

Of Data Availability, & the Great Library of Blobs

commitments FIG. VI
Fig. VI. — The Great Library of Blobs, with floor-to-ceiling shelves of leather-bound data, a rolling ladder bearing a librarian-validator, and the central card-catalogue of cryptographic commitments.

It avails little to compress the labour of computation, if the data upon which that labour was performed is forthwith mislaid. The principle of data availability requires that any rollup, having submitted its parcel, must also publish the underlying data — that any honest party may, in time of dispute, reconstruct the parcel and verify it for himself.

The matter is most readily understood by analogy with the great Library at Alexandria. The bookseller (the rollup) may publish a great compendium of accounts; but unless the original ledgers (the data blobs) are deposited with the librarian (the principal chain or a dedicated availability layer), no scholar may afterwards verify the bookseller's arithmetic.

Several systems of availability are now in use: the Calldata Method (in which the data is published directly upon the principal chain); the Blob Method (in which the data is published in dedicated ephemeral compartments, after the manner of EIP-4844); and the Committee Method (in which a learned committee attests to the data's existence, — though this last is held by the more rigorous to be a compromise).

  • ❦ Calldata. — Costly, but most secure.
  • ❦ Blobs. — Cheaper, & ephemeral.
  • ❦ Committees. — Cheapest, but trust-laden.