Specify Granite protocol upgrade (#321)

* Specify Granite protocol upgrade

* Update specs/protocol/granite/derivation.md

Co-authored-by: clabby <[email protected]>

* clarify activation timestamp for channel frames

---------

Co-authored-by: clabby <[email protected]>
Co-authored-by: Mark Tyneway <[email protected]>

specs/protocol/granite/derivation.md

@@ -0,0 +1,23 @@
+# Granite L2 Chain Derivation Changes
+
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+**Table of Contents**
+
+- [Protocol Parameter Changes](#protocol-parameter-changes)
+- [Reduce Channel Timeout](#reduce-channel-timeout)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+
+## Protocol Parameter Changes
+
+The following table gives an overview of the changes in parameters.
+
+| Parameter | Pre-Granite (default) value | Granite value | Notes |
+| --------- | ------------------------- | ----------- | ----- |
+| `CHANNEL_TIMEOUT` | 300 | 50 | Protocol Constant is reduced. |
+
+## Reduce Channel Timeout
+
+With Granite, the `CHANNEL_TIMEOUT` is reduced from 300 to 50 L1 Blocks.
+The new rule activation timestamp is based on the blocktime of the L1 block that the channel frame is included.

specs/protocol/granite/exec-engine.md

@@ -0,0 +1,18 @@
+# L2 Execution Engine
+
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+**Table of Contents**
+
+- [EVM Changes](#evm-changes)
+  - [`bn256Pairing` precompile input restriction](#bn256pairing-precompile-input-restriction)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+
+## EVM Changes
+
+### `bn256Pairing` precompile input restriction
+
+The `bn256Pairing` precompile execution has additional validation on its input.
+The precompile reverts if its input is larger than `112687` bytes.
+This is the input size that consumes approximately 20 M gas given the latest `bn256Pairing` gas schedule on L2.

specs/protocol/granite/overview.md

@@ -6,17 +6,15 @@
 
 - [Execution Layer](#execution-layer)
 - [Consensus Layer](#consensus-layer)
-- [Smart Contracts](#smart-contracts)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 
 This document is not finalized and should be considered experimental.
 
 ## Execution Layer
 
-## Consensus Layer
+- [Limit `bn256Pairing` precompile input size](./exec-engine.md#bn256pairing-precompile-input-restriction)
 
-## Smart Contracts
+## Consensus Layer
 
-- [Custom Gas Token](./custom-gas-token.md)
-- [Predeploys](./predeploys.md)
+- [Reduce Channel Timeout to 50](./derivation.md#reduce-channel-timeout)