From d64b4e7d245438bd6db0617f7eee619bbf7d7eee Mon Sep 17 00:00:00 2001 From: Alex Stokes Date: Tue, 8 Jun 2021 13:44:06 -0500 Subject: [PATCH] Add `message.topic` to gossipsub `message-id` in Altair --- specs/altair/p2p-interface.md | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/specs/altair/p2p-interface.md b/specs/altair/p2p-interface.md index d6f8a0dfe..49082452f 100644 --- a/specs/altair/p2p-interface.md +++ b/specs/altair/p2p-interface.md @@ -74,6 +74,15 @@ New topics are added in Altair to support the sync committees and the beacon blo The specification around the creation, validation, and dissemination of messages has not changed from the Phase 0 document. +The derivation of the `message-id` has changed starting with Altair to incorporate the message topic along with the message data. +The `message-id` MUST be the following 20 byte value computed from the message: +* If `message.data` has a valid snappy decompression, set `message-id` to the first 20 bytes of the `SHA256` hash of + the concatenation of `MESSAGE_DOMAIN_VALID_SNAPPY` with the snappy decompressed message data and the topic name, + i.e. `SHA256(MESSAGE_DOMAIN_VALID_SNAPPY + snappy_decompress(message.data) + message.topic)[:20]`. +* Otherwise, set `message-id` to the first 20 bytes of the `SHA256` hash of + the concatenation of `MESSAGE_DOMAIN_INVALID_SNAPPY` with the raw message data and the topic name, + i.e. `SHA256(MESSAGE_DOMAIN_INVALID_SNAPPY + message.data + message.topic)[:20]`. + The new topics along with the type of the `data` field of a gossipsub message are given in this table: | Name | Message Type |