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Iroha 2 Documentation

Iroha is a fully-featured blockchain ledger. With Iroha you can:

  • Create and manage custom fungible assets, such as currencies, gold, and others
  • Create and manage non-fungible assets
  • Manage user accounts with a domain hierarchy and multi-signature transactions
  • Use efficient portable smart contracts implemented either via WebAssembly or Iroha Special Instructions
  • Use both permissioned and permission-less blockchain deployments

How Iroha works

To understand how Iroha operates, let's draw parallels between a blockchain and a computer. If the blockchain is the computer, then in this metaphor of ours the client binary (for example: iroha_client_cli) is the keyboard, the blockchain is the hard drive, and the Iroha peer software is the processor. Like a processor, Iroha accepts portable instructions that modify what's written to the blockchain, allow certain users to use the network, and lock others out.

Any operation that is run on-chain is written in terms of Iroha Special Instructions (ISI), and there is no other way of modifying the world state.

Each interaction with the blockchain is done via a transaction. A transaction is a collection of instructions, which are either glued together in sequence or compiled into what we affectionately call a WASM blob. You need these instructions to register an account, remove an account, add X amount of Y currency, and so on.

To read the information encoded in the blocks of a blockchain (the current world state), you use queries. Queries are submitted like instructions, but they're not tracked and recorded in blocks, so they're much more lightweight. If you use queries as part of complicated logic (e.g. inside WASM), they have a non-negligible impact on the size of the blocks. Queries that are only used to get information leave no trace in the blockchain.

If you have previously worked with Iroha, start with our comparison of Iroha 1 and Iroha 2. That will help you understand the differences between the two versions and upgrade to the newer one.

Check the tutorial part of this documentation where you can follow one of the available language-specific guides in Bash, Rust, Kotlin, Javascript, or Python. The guides introduce you to the basic concepts and provide code snippets that you can run yourself.

In the Blockchain chapter you can find documentation for Iroha features, such as Iroha Special Instructions, triggers, queries.

The Configuration and Management section explains Iroha 2 configuration files in greater detail and covers topics such as public key cryptography, peer management, and public and private modes.

Learn More

For more information on Iroha 2, please take a look at the Iroha 2 Whitepaper, as well as the Hyperledger Iroha section within the Hyperledger Foundation Wiki.

For more information on Iroha 1, take a look at the Iroha 1 documentation.


If you want to contribute to Hyperledger Iroha, please look at our Contributing Guide.