Optimistic access lists


#1

Access list incentives mean transactions should rarely throw an ACCESS_LIST_EXCEPTION by accessing state outside of the access list. By having users provide two transaction signatures (only one of which is included onchain) we can save from having onchain access lists whenever an ACCESS_LIST_EXCEPTION is not thrown. This reduces onchain transaction sizes, saves gas, and possibly improves privacy.

Construction

Let T be an unsigned transaction (without the access list) and let A be the corresponding unsigned access list. Currently a user sends T, A and sig([T, A]) to validators. We suggest instead that the user sends the following:

  • Unsigned transaction: T
  • Unsigned access list: A
  • Optimistic signature: sig(T)
  • Exceptional signature: sig([T, A])

Validators execute T relative to A. Two cases may arise:

  1. Optimistic: No ACCESS_LIST_EXCEPTION is thrown, in which case only T and sig(T) must be included onchain.
  2. Exceptional: An ACCESS_LIST_EXCEPTION is thrown, in which case T, A and sig([T, A]) must be included onchain.

#2

Makes a lot of sense, though it’s important to note that this only saves ~20 * len(A) bytes, whereas we can expect the witness to be ~800 * len(A). I’d rather burn protocol complexity points on multi-state roots or partial statelessness than this.