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Chapter 1
Espresso Confirmation Layer

Contents



1.1 Overview
1.2 Architecture


1.1 # Overview

Espresso’s global confirmation layer (GCL) provides agreement on the inputs to a collection of composable blockchains. The key properties provided by the GCL are:

# Globally trusted: All blockchains which wish to compose trust Espresso GCL. Ultimately, this trust is a convention taken by each individual chain, by enshrining some assumption about the GCL into their state transition function (STF). However, the GCL aims to be trustworthy via cryptoeconomic security: once some input has been confirmed by the GCL, it cannot be rolled back without mass collusion and a large amount of economic collateral being burned.

Warning: 

this requirement is lacking acceptance criteria and should be refined.


# Fast: The GCL confirms sequences of blockchain inputs much faster than they would be confirmed by the settlement layer .

Warning: 

this requirement is lacking acceptance criteria and should be refined.


# Verifiable: Once the GCL has confirmed an input, anybody can quickly and efficiently verify that that input has been confirmed, by means of a succinct cryptographic proof.

Warning: 

this requirement is lacking acceptance criteria and should be refined.


Together, these properties mean that inputs to any chain using the GCL can be quickly confirmed and verified by any other chain trusting the GCL. Since the chain state is derivable or verifiable (and in some cases provable) from the inputs (by applying an STF), this makes it possible and fast for chains to mutually verify each other’s state. Thus, the Espresso GCL forms the foundation for a composable multi-chain world.

1.2 # Architecture

TODO give a somewhat detailed overview of the architecture; not merely listing the components but describing briefly what they are for and how they interact. Include a top level architecture diagram. For now, the links listed here demonstrate how you would use this overview page to navigate the rest of the book.

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