Add EIP: General purpose execution layer requests

EIPS/eip-7685.md

@@ -0,0 +1,76 @@
+---
+eip: 7685
+title: General purpose execution layer requests
+description: A general purpose bus for sharing EL triggered requests with the CL
+author: lightclient (@lightclient)
+discussions-to: https://ethereum-magicians.org/t/eip-7685-general-purpose-execution-layer-requests/19668
+status: Draft
+type: Standards Track
+category: Core
+created: 2024-04-14
+---
+
+## Abstract
+
+This proposal defines a general purpose framework for propagating contract-triggered requests from execution layer to the consensus layer. It extends the header and body with only a single field each to store the request information.
+
+## Motivation
+
+The proliferation of smart contract controlled validators has caused there to be a demand for additional EL triggered behaviors. By allowing these systems to delegate administrative operations to their governing smart contracts, they can avoid intermediaries needing to step in and ensure certain operations occur. This creates a safer system for end users.
+
+## Specification
+
+### Execution Layer
+
+#### Request
+
+A `Request` consists of a `RequestType` prepended to an opaque byte array `RequestData`.
+
+```
+Request = RequestType ++ RequestData
+```
+
+Let `Requests` be the list of all `Request` objects in the block in ascending order by type.
+
+#### Header
+
+Extend the header with a new 32 byte value `RequestsRoot`.
+
+Let `RequestsRoot` be the root of a Merkle-Patricia trie keyed by the index in the list of `Requests`. This is equivalent to how the transaction trie root is computed.
+
+### Consensus Layer
+
+Each proposal may choose how to extend `ExecutionPayload` to include the new EL request.
+
+A additional processing step is be added to `process_execution_payload` to iterate over and process all requests.
+
+## Rationale
+
+### Opaque byte array rather than an RLP array
+
+By having the second byte on be opaque bytes, rather than an RLP (or other encoding) list, we can support different encoding formats for the transaction payload in the future such as SSZ, LEB128, or a fixed width format.
+
+### Request source and validity
+
+This EIP makes no strict requirement where a request may come from nor when/how a request must be validated. This is to provide future protocol designers maximum flexibility.
+
+The authors' recommendations on source and validity of requests are:
+
+* The source of requests should be from the execution of transactions. More specifically, transactions which make calls to designated system contracts that store the request in account. The storage would later be retrieved by a post-block system call to the contract. Alternatively, if the system call does not need to be inherently concerned with rate limiting, it could rely simply on emitting an event which is later parsed post-block by the system and converted into a request.
+* A request's validity can often not be fully verified at the execution layer. This is why they are referred to merely as "requests"; they do not carry the authority on their own unilaterally catalyze and action. We expect the system contracts to perform whatever validation is possible by the EL and then pass it on to the CL for further validation.
+
+## Backwards Compatibility
+
+No backward compatibility issues found.
+
+## Test Cases
+
+TODO
+
+## Security Considerations
+
+Needs discussion.
+
+## Copyright
+
+Copyright and related rights waived via [CC0](../LICENSE.md).