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Network Upgrades

For details on why and how network upgrades happen, along with explanations of the various types, please see the Upgrades overview and Upgrade methods sections further down.

Upcoming upgrades

New PoW algorithm


To help ensure Quality of Service on the network by providing the ability to generate and validate PoW using a new algorithm. This algorithm will be more memory-hard causing the resources required for generating transactions to shift accordingly.

Transition details

Date Type Description
TBD Node release Nano node V20.0 released to include a new PoW server and epoch block support. These are only foundational updates and will not be configured for activation in this release.
TBD Node release Nano node VXX.X released to include new PoW algorithm in PoW server, addition of a new state block version (v2) with support for the new work values and final changes allowing transition via epoch blocks.
TBD Epoch blocks start Distribution of epoch blocks to each account which upgrades them to use the new state block version (v2). Once an account is upgraded nodes will only validate work made using the new PoW algorithm for that account.
TBD Epoch blocks end Distribution of epoch blocks ends after all accounts are upgraded.

Nodes de-peered with epoch blocks

Due to the nature of the state block changes to be included in the 2nd node release of this transition, any nodes not updated to the latest version at the time of epoch block distribution will be de-peered as part of this process.

Transition Explanation

In the above transition plan a phased node upgrade was used to provide support for some foundational elements of the new PoW algorithm while further details of the design are worked out. The epoch block distribution in this transition represents a clean switch from one PoW algorithm to the other - no block in the ledger is allowed to have work generated by either PoW, instead older block versions must use the existing PoW and new block versions must use the newer PoW.

This clean switch comes with benefits including reduction in code complexity related to handling two types of PoW generation and validation for the same block versions, and the setting of a clear point in the ledger for each account where work values changed - potentially useful for future snapshoting.

To mitigate the impacts of this approach the Nano Foundation will be communicating regularly about progress and monitoring closely the activity on the network to ensure proper conditions exist to finalize the transition.

Past upgrades

State blocks


The upgrade to state blocks involved multiple node releases and three different actions on the network including distribution of two canary blocks and the first epoch blocks.

Transition Details

Date Type Description
2018-03-23 Node release Nano node V11.0 released with support for state blocks built-in but not yet activated.
2018-04-11 Canary block Parse canary block distributed which enabled parsing of state blocks by nodes so manual generation of that block type would be accepted on the network going forward. This action was performed after a majority of the network upgraded to the required V11.0 to allow confirmations to occur on this new block type.
2018-05-20 Canary block Generation canary block distributed which forced the generation of state blocks by nodes going forward. At this point both state and legacy type (open, send, receive, change) blocks remain valid on the network.
2018-08-20 Node release Nano node V15.0 released with support for epoch blocks built-in and away distribution.
2018-10-25 Epoch blocks start Distribution of epoch blocks begins.
2019-05-24 Epoch blocks end Distribution of epoch blocks is finished. All accounts, opened and unopened, are now capped and can no longer attempt inserting legacy style blocks.



The upgrade to include the vote-by-hash feature was based on a hardcoded timestamp in the node. After this time nodes began voting using this new feature.

Transition Details

Date Type Description
2018-08-22 Node release Nano node V15.2 release with support for vote-by-hash but not yet activated.
00:00:00 UTC
Hardcoded date Nodes upgraded to V15.2 began voting using the vote-by-hash method. Nodes not yet upgraded would fail to properly interpret votes so were no longer compatible with the network.

Upgrades overview

Nano is a protocol, an agreed upon standard that allows computers to communicate with each other and agree on data. Because of these communication standards, having mechanisms that force all nodes to upgrade certain behaviors at the same time is critical to the consensus and consistency in the network.

In most blockchain networks these upgrades can be scheduled to take effect once a particular block height is hit because all nodes operate off a single, synchronous chain. Due to the Nano network being asynchronous this method doesn’t work, so instead we need methods for upgrading accounts asynchronously.

There are a couple different options for handling these upgrades and the process is currently managed primarily by the Nano Foundation. The upgrades are tested on the beta network to ensure all components are behaving as expecting before being considered for updating on the main network. If the behavior being changed involves consensus, any manual upgrade actions are triggered once a large majority of nodes and major services have upgraded.

Of course many features, including protocol changes, can be activated immediately with a new node release, so these network upgrade scenarios are only reserved for certain cases. Options for providing better agreement on capabilities between nodes has been discussed in this GitHub issue. There is also a discussion around how to potentially automate network upgrade processes in this forum topic:

Upgrade methods

There are various methods used to upgrade and a brief overview of each, along with benefits and drawbacks, are included below. Upgrades for behaviors contained and activated with a single node release are not included as they are the foundation on top of which these other methods are made capable.

Phased node upgrades

A feature is introduced in a node release but not activated for use across the network until a subsequent node release. See State block upgrade details for an example.

Trigger Uses blocks Benefits Drawbacks
Multiple node upgrades No
  • No manual intervention or automated process needed
  • Uses already established upgrade process node operators are used to
  • Longer time period to get feature activated
  • Cannot be used to perform upgrades needed simultaneously across the network

Hardcoded date

A date is hardcoded into the node release to activate a feature or behavior at a specific time in the future. See Vote-by-Hash upgrade details for an example.

Trigger Uses blocks Benefits Drawbacks
Node upgrade + specific date No
  • Simple to implement
  • No manual activity required
  • Inability to adjust timing without rushing new release out

Canary block(s)

The hash of a block is hardcoded in the node such that once that hash is seen by the node, it will activate a feature or behavior. Multiple block hashes can be used to perform different phases of a transition. See State blocks upgrade details for an example.

Trigger Uses blocks Benefits Drawbacks
Node upgrade + distribution of one block per transition phase Yes
  • Can be used for multi-phase upgrades, including in combination with other options
  • Timing flexible
  • Requires manual intervention
  • Adds additional code complexity
  • Can cause unchecked table to fill during transition

Epoch blocks

A special block type that can only be generated using a pre-determined private key. These will be accepted by nodes and be attached as the frontier blocks on each account-chain on the network. This feature was built to allow very limited controls using these blocks: they cannot change account balances or representatives, only upgrade the account versions to allow new block structures. See State block upgrade details for an example.

Trigger Uses blocks Benefits Drawbacks
Node upgrade + distribution of epoch blocks Yes
  • Provides clean upgrade markers directly within the ledger on every account-chain
  • Timing flexible
  • Ability to asynchronously upgrade block versions even for inactive/unopened account chains
  • Requires manual intervention
  • Introduces ability for non-account owner to write to account chain in a highly restricted way
  • Adds additional code complexity
  • Requires large volume of blocks