Mar 16, 2020

Algorand Co-Chains

By: Silvio Micali


The public, permissionless blockchain enables all organizations, individuals, and governments to transact with efficiency, security, and transparency, both internally and with each other.  It also enables private enterprises to expand their addressable markets, increase revenue, generate new product opportunities, and more.  

Public permissionless blockchains, however, are not always well-suited to organizations such as finance, banking, government, health care, and others that must carefully control who can access their data, and comply with complex regulatory requirements. Instead, a private permissioned blockchain can provide the level of rigorous fine-grained control needed by such organizations. Nevertheless, private permissioned blockchains run the risk of isolating their users. By making public and private blockchains interoperable, organizations can isolate and control sensitive data on a private blockchain while still safely interacting with the world at large through an interoperable public blockchain. 

At Algorand, we have been developing our co-chain architecture to enjoy the advantages of both types of blockchain. Essentially, a co-chain 

  1. Is totally independent from the public chain, shields its transactions from all outsiders, chooses its own validators, and runs its own Algorand consensus algorithm;
  2. Interoperates with the Algorand main chain to transact with other co-chains, and everyone else, with the same ease and security with which the members of Algorand’s permissionless chain transact with each other; and  
  3. Enjoys, both in its internal and external interactions, the same atomic transactions, layer-1 smart contracts, and all other primitives and tools offered by the permissionless Algorand protocol. In fact, it automatically inherits all the improvements and upgrades that will be added to Algorand’s permissionless protocol. 


The world needs both permissionless and permissioned blockchains. Algorand provides best-of-breed implementations for both. More importantly, Algorand guarantees their synergy. No matter how scalable, distributed, and secure a permissioned chain may be, its members may not want to interact only with each other, but also with other chains and with the world at large. 

The Algorand co-chain architecture enables the members of a permissioned chain to work most securely and efficiently not only with each other, but also, while retaining maximum autonomy, with the Algorand permissionless chain and members of other chains as well. 

* The Algorand Co-Chain architecture has been developed by Sergey Gorbunov, Maurice Herlihy and Silvio Micali. Their full technical paper will be published in the near future.