The 1.x Files: January call digest

January 14th tl;dc (too lengthy, did not call)

Disclaimer: It is a digest of the subjects mentioned within the recurring Eth1.x analysis call, and would not characterize finalized plans or commitments to community upgrades.

The major subjects of this call have been

  • Tough information quantifying benefits of switching to a binary trie construction
  • Transition methods and potential challenges for a swap to binary tries
  • “Merklizing” contract code for witnesses, and implications for fuel scheduling/metering
  • Chain pruning and historic chain/state information — community implications and approaches to distribution.


The weekend following EthCC (March 7-8), there will probably be a small 1.x analysis summit, with the intent of getting just a few days of stable dialogue and work on the subjects at hand. The session will probably be capped (by venue constraints) at 40 attendees, which needs to be greater than sufficient for the members anticipated.

There may also possible be some casual, ad-hoc gathering round Stanford Blockchain week and ETHDenver, however nothing explicitly deliberate.

The subsequent call is tentatively scheduled for the primary or second week in February — half-way between now and the summit in Paris.

Technical dialogue

EIP #2465

Though indirectly associated to stateless ethereum, this EIP improves the community protocol for transaction propagation, and is thus a reasonably simple enchancment that strikes issues in the correct route for what analysis is engaged on. Assist!

Binary Trie dimension financial savings

Transitioning to a binary trie construction (as an alternative of the present hexary trie construction) ought to in concept scale back the scale of witnesses by one thing like 3.75x, but in practice that reduction might only be about half, depending on how you look at it..

Witnesses are about 30% code and 70% hashes. Hashes inside the trie are decreased by 3x, however code shouldn’t be improved with a binary trie, because it all the time must be included within the witness. So switching to a binary trie format will convey witness sizes to ~300-1400kB, down from ~800-3,400kB within the hexary trie.

Making the swap

Enacting the precise transition to a binary trie is one other matter, with just a few questions that must be fleshed out. There are basically two totally different attainable methods that may very well be adopted:

progressive transition — It is a ‘ship of Theseus’ mannequin of transition whereby the whole state trie is migrated to a binary format account-by-account and storageSlot-by-storageSlot, as every a part of state is touched by EVM execution. This means that, forevermore, Ethereum’s state can be a hexary/binary hybrid, and accounts would must be “poked” with a purpose to be up to date to the brand new trie format (perhaps with a POKE opcode ;). The benefits are that this doesn’t interrupt the conventional functioning of the chain, and doesn’t require large-scale coordination for upgrading. The drawback is complexity: each hexary and binary trie codecs must be accounted for in purchasers, and the method would by no means truly “finish”, as a result of some elements of the state can’t be accessed externally, and would must be explicitly poked by their house owners which in all probability wont occur for the whole state. The progressive technique would additionally require purchasers to change their database to be a type of ‘virtualized’ binary trie inside a hexary database structure, to keep away from a sudden dramatic improve in storage necessities for all purchasers (be aware: this database enchancment can occur unbiased of the complete ‘progressive’ transition, and would nonetheless be helpful alone).

compute and clean-cut — This could be an ‘without delay’ transition achieved over a number of hard-forks, whereby a date sooner or later can be chosen for the swap, after which all members within the community would wish to recompute the state as a binary trie, after which swap to the brand new format collectively. This technique can be in some sense ‘easier’ to implement as a result of it is simple on the engineering facet. Nevertheless it’s extra advanced from a coordination perspective: The new binary trie state must be pre-computed earlier than the fork which may take an hour (or thereabouts) — throughout that window, its not clear how transactions and new blocks can be dealt with (as a result of they might must be included within the yet-un-computed binary state trie, and/or the legacy trie). This course of can be made tougher by the truth that many miners and exchanges want to improve purchasers on the final second. Alternatively we may think about halting the whole chain for a short while to re-compute the brand new state — a course of which is perhaps even trickier, and doubtlessly controversial, to coordinate.

Each choices are nonetheless ‘on the desk’, and require additional consideration and dialogue earlier than any choices are made as regards to subsequent steps. Specifically weighing the trade-offs between implementation complexity on one hand and coordination challenges on the opposite.

Code “chunking”

Addressing the code portion of witnesses, there was some prototyping work performed on code ‘merklization’, which basically permits contract code to be break up up into chunks earlier than being put right into a witness. The primary thought being that, if a way in a wise contract is named, the witness ought to solely want to incorporate the elements of the contract code that have been truly referred to as, moderately than the whole contract. That is nonetheless very early analysis, nevertheless it suggests a further ~50% discount within the code portion of a witness. Extra ambitiously, the observe of code chunking may very well be prolonged to create a single international ‘code trie’, however this isn’t a properly developed thought and certain has challenges of its personal that warrant additional investigation.

There are totally different strategies by which code might be damaged up into chunks, after which be used to generate witnesses. The first is ‘dynamic’, in that it depends on discovering JUMPDEST directions, and cleaving close to these factors, which ends up in variable chunk sizes relying on the code being damaged up. The second is ‘static’, which might break up code into fastened sizes, and add some crucial metadata specifying the place right bounce locations are inside the chunk. It looks like both of those two approaches can be legitimate, and each is perhaps suitable and may very well be left as much as customers to resolve which to make use of. Both manner, chunking allows an extra shrinking of witness sizes.


One open query is what adjustments can be crucial or fascinating in fuel scheduling with the introduction of block witnesses. Witness technology must be paid for in fuel. If the code is chunked, inside a block there can be some overlap the place a number of transactions cowl the identical code, and thus elements of a block witness can be paid for greater than as soon as by all of the included transactions within the block. It looks like a secure thought (and one that might be good for miners) can be to go away it to the poster of a transaction to pay the complete price of their very own transaction’s witness, after which let the miner maintain the overpayment. This minimizes the necessity for adjustments in fuel prices and incentivizes miners to supply witnesses, however sadly breaks the present safety mannequin of solely trusting sub-calls (in a transaction) with a portion of the overall dedicated fuel. How that change to the safety mannequin is dealt with is one thing that must be thought of totally and totally. On the finish of the day, the aim is to cost every transaction the price of producing its personal witness, proportional to the code it touches.

Wei Tang’s UNGAS proposal would possibly make any adjustments to the EVM simpler to perform. It isn’t strictly crucial for stateless Ethereum, however it’s an thought for learn how to make future breaking adjustments to fuel schedules simpler. The query to ask is “What do the changes look like both without and with UNGAS — and those things considered, does UNGAS actually make this stuff significantly easier to implement?”. To reply this, we want experiments that run issues with merklized code and new fuel guidelines appled, after which see what ought to change with regard to price and execution within the EVM.

Pruning and information supply

In a stateless mannequin, nodes that would not have some or all the state want a option to sign to the remainder of the community what information they’ve and what information they lack. This has implications for community topology — stateless purchasers that lack information want to have the ability to reliably and rapidly discover the info they want someplace on the community, in addition to broadcast up-front what information they do not have (and would possibly want). Including such a function to one of many chain-pruning EIPs is a networking (however not consensus) protocol change, and its one thing that additionally might be performed now.

The second facet of this downside is the place to retailer the historic information, and the perfect answer to date proposed is an Eth-specific distributed storage community, that may serve requested information. This might are available many flavors; the entire state is perhaps amenable to ‘chunking’, much like contract code; partial-state nodes may watch over (randomly assigned) chunks of state, and serve them by request on the sides of the community; purchasers would possibly make use of extra information routing mechanism so {that a} stateless node can nonetheless get lacking information by means of an middleman (which does not have the info it wants, however is linked to a different node that does). Nonetheless it is carried out, the final aim is that purchasers ought to be capable of be part of the community and be capable of get all the info they want, reliably, and with out jockying for place connecting to a full-state node, which is successfully what occurs with LES nodes now. Work surrounding these concepts continues to be in early phases, however the geth crew has some promising outcomes experimenting with ‘state tiling’ (chunking), and turbo-geth is engaged on information routing for gossiping elements of state.

As all the time, when you have questions on Eth1x efforts, requests for subjects, or wish to contribute, attend an occasion, come introduce your self on or attain out to @gichiba and/or @JHancock on twitter.

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