From 8600253aa070f53572da992208f87f4981f81125 Mon Sep 17 00:00:00 2001
From: mjalalzai <33738574+MForensic@users.noreply.github.com>
Date: Tue, 5 Sep 2023 08:21:54 -0700
Subject: [PATCH] Update spec.md

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 carnot/spec.md | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

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  Carnot avoids the chain reorg problem, making it compatible with PoS schemes
  This enhances the robustness of the protocol, making it a valuable addition to the ecosystem of consensus protocols
 
+# The Protocol
+ The protocol in Carnot operates in two modes: the happy path and the unhappy path.
+
+ In Carnot, nodes are arranged in a binary tree overlay committee structure. Moreover, Carnot is a
+ pipelined consensus protocol where a block contains the proof of attestation of its parent. In happy path the
+ leader proposes a block that contains a quorum certificate (QC) with votes from more than two-thirds of the root
+ committee and its child committee/ committees. The voting process begins at the leaf committee where nodes verify
+ the proposal and send their votes to the parent committee. Once a node in the parent committee receives more than
+ two-thirds of the votes from its child committee members, it sends its votes to its parent. This process continues
+ recursively until the root committee members collect votes from its child committee/ committees. The root committee
+ member builds a QC from the votes and sends it to the next leader. The leader builds a QC and proposes the next block
+ upon receiving more than two-thirds of votes.
+
+
+ In the unhappy path, if a node does not receive a message within a timeout interval, it will timeout. Only nodes at
+ the root committee and its child committee/ committees send their timeout messages to the root committee. The root
+ committee builds a timeout QC from more than two-thirds of messages, recalculates the new overlay, and broadcasts it
+ to the network. Similar to the happy path, the timeout message moves from leaves to the root. Each parent waits for
+ more than two-thirds of timeout messages from its child committees and sends its timeout to the parent committee once
+ the threshold is reached. A node in the root committee builds a QC from timeout messages received from its
+ child committee/committees and forwards it to the next leader. Upon receiving more than two-thirds of timeout
+ messages, the next leader builds an aggregated QC and proposes the next block containing the aggregated QC.
+ It should be noted that while receiving timeout messages, each node also updates its high_qc (the most recent QC)
+ and passes it to its parent through the timeout message. In this way, the aggregated QC will include the high_qc seen
+ by the majority of honest nodes. Hence, after the view change, the protocol safety is preserved.
+
 # Carnot Specification
 This is the pseudocode specification of the Carnot consensus algorithm.
 In this specification we will omit any cryptographic material, block validity and proof checks. A real implementation is expected to check those before hitting this code.