Analog : The Next-Gen Layer 1 for Cross-Chain Interoperability 🚀

Key Highlights
1. Introduction
2. Date of TGE

Thanks to @OneAnalog for reviewing our technical summary.

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In this thread, we explore the Analog blockchain, an interoperability layer that facilitates communication between connected blockchain networks. Analog not only enables General Message Passing (GMP), allowing the transfer of arbitrary messages between heterogeneous blockchains, but it also supports native smart contracts, enabling users and developers to interact with any chain directly from the Analog network.

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High-Level Overview of Analog Architecture
Analog is an externally verified bridge type, using its blockchain called Timechain to verify cross-chain messages. Analog's architecture is divided into three layers:

1.Chain Layer: This is where the blockchains connected to Analog reside.

2.Connector Layer: This layer includes connectors (also known as relayers) and chronicle workers who fetch data from source chains to the Timechain and push data from the Timechain to destination chains. Simply put, the Connector Layer facilitates communication between the Timechain and the Chain Layer.

3.Timechain: This is where the Analog network resides. The Analog network is maintained by a decentralized set of validator nodes called time nodes. Data fetched from the Chain Layer goes through the Timechain consensus before becoming available for use. The Timechain also supports smart contracts, called Continuum smart contracts, which allow users and dApps to manipulate assets on different chains or initiate cross-chain interactions directly from the Timechain.

A Simplified Explanation of How Analog Works
Based on the previous infographic, here is how Analog enables communication between connected chains:

1.Connectors monitor connected chains for cross-chain requests. They fetch data from these chains and relay it to the relevant chronicle workers, who sign to attest to the validity of the data before passing it to the Timechain.

2.A time elector (a block proposer) proposes a block containing the signed data from step 1.

3.A set of chosen time nodes then cooperates and votes on the proposed block. If the block is accepted by a quorum of time nodes (two-thirds), it can be forwarded to the destination chains.

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Diving Deeper into Analog
The previous explanation provides a simplified version of how Analog works. In fact, there are more details and steps, like shards and threshold signatures, that we have not covered yet in the above explanation. Let's dive deeper into each layer and its components to truly understand the Analog network.

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Chain Layer
We will start from the outermost layer, the Chain Layer. The Analog network acts as an interoperability layer, allowing heterogeneous blockchains to connect and communicate with each other. The Chain Layer is where these blockchains reside.

To establish connectivity between these chains and Analog, an Analog gateway smart contract is deployed on each connected chain, where connectors are assigned to monitor the gateways for incoming cross-chain requests. Analog plans to support EVM-based, Cosmos-based, and Polkadot chains.

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Connector Layer
In this layer, there are three important components: connectors, chronicle workers, and collector workers.

- Connectors: Connectors interact with external chains, relaying cross-chain requests to chronicle workers and executing transactions on external chains.

- Chronicle Workers: Chronicle workers cooperate to attest to the validity of data received from connectors before submitting it to the Timechain.

- Collector Workers: A collector worker is a selected chronicle worker from each shard. It acts as a leader, coordinating threshold signing processes for chronicle workers within its shard.

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Connector Layer: Connectors
Each time node runs one or more connectors and one chronicle worker. The connectors are responsible for observing gateway smart contracts on external chains and relaying relevant messages to their corresponding chronicle worker. Connectors receive a share of block rewards and the transaction fees paid to Analog for their services.

Another responsibility of connectors is to relay cross-chain messages to external chains so that the gateway smart contracts on the destination chains can execute cross-chain requests. A gateway smart contract can execute an action only if it receives a valid signed transaction generated from more than two-thirds of chronicle workers using a Threshold Signature Scheme (TSS), which will be explained next.

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Connector Layer: Chronicle Workers
A chronicle worker, maintained by each time node, cooperates with other chronicle workers and reaches consensus on the validity of the data received from its connectors using a Threshold Signature Scheme (TSS) before forwarding it to the Timechain. Chronicle workers essentially form an oracle network for Analog, deciding whether to accept or reject data from connectors.

For scalability, the network of chronicle workers is partitioned into shards, where each shard consists of a set of independent chronicle workers tasked with signing messages from a specific set of chains. For example, shard 1 consists of chronicle workers 1, 2, and 3, who only sign messages from chains A, B, and C. Meanwhile, shard 2 consists of chronicle workers 4, 5, and 6, who sign messages from chains D, E, and F. Within each shard, there is one specially assigned chronicle worker called a collector worker.

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Connector Layer: Collector Workers
A collector worker acts as a leader in TSS processes, coordinating the KEYGEN and KEYSIGN processes. Roughly speaking, assume there are “k” chronicle workers in a shard. The KEYGEN process generates a private key, divides it into “k” fragments, and distributes each key fragment to an independent chronicle worker. This means that fragment f_1 goes to chronicle worker 1, fragment f_2 goes to chronicle worker 2, and so on, ensuring that no individual party in the shard, including the collector, has knowledge of the full private key. To reconstruct the original private key, only “t” out of k key fragments are required, and in Analog, t is set to be two-thirds of the number of chronicle workers in a shard.

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During the KEYSIGN step, when a chronicle worker wants to attest to a cross-chain message received from its corresponding connector, each chronicle worker signs the message using its key fragment and sends the signed message to the collector worker. If the collector worker can collect more than two-thirds (a super majority or a quorum) of the signed messages from chronicle workers in its shard, it can use the received messages signed with partial keys to reconstruct the same message but signed with the complete key. The collector worker can then forward this message with the valid signature to the Timechain.

***Note that this scheme can be used to create transactions to update the state on connected chains.