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This repository contains the reference implementation of Alephium, a sharded blockchain that makes programmable money scalable and secure. For more information, please visit the wiki.


The protocol's innovations extend battle-tested ideas from Bitcoin and Ethereum:

  • BlockFlow algorithm based on UTXO model enables sharding and scalability for today (code + algorithm paper)
    • The first sharding algorithm that supports single-step cross-shard transactions, offering the same user experience as single chain
    • Simple and elegant PoW based sharding, does not rely on beacon chain
  • Stateful UTXO model combines the advantages of both eUTXO model and account model (see code, wiki to come)
    • Tokens are first-class citizens and UTXO-based, which are owned by users directly instead of contracts
    • Offer the same expressiveness as account model. DApps can be easily built on top of it with better security
    • Support multiple participants in a single smart contract transaction. Multiple calls can be packed into a single transaction too.
  • Novel VM design resolves many critical challenges of dApp platforms (see code, wiki to come)
    • Less IO intensive
    • Flash loan is not available by design
    • Eliminate many attack vectors of EVM, including unlimited authorization, double dip issue, reentrancy attack, etc
    • UTXO style fine-grained execution model reduces risk-free arbitrage
  • PoLW algorithm reduces the energy consumption of PoW in the long term (research paper)
    • Adaptive rewards based on hashrate and timestamp are designed and implemented
    • Internal mining cost through burning will be activated when hashrate and energy consumption is significantly high



The following dependencies must be installed in order to run the JAR deliverable:

  • java (11+)


You can obtain our latest single JAR distribution from the GitHub releases and start the application using the following command:

java -jar alephium-<VERSION>.jar

Build From Source


In order to build the project from source the following dependencies must be installed on your system:

  • java (11+)
  • SBT

Single JAR

Use the following command to build a single runnable JAR :

make assembly

The resulting assembly file will appear in /app/target/scala-2.13/ directory.

Universal Zip distribution

Use the following command to build a zip distribution including launch scripts:

make package

The resulting package file will appear in the app/target/scala-2.13/universal directory.

Docker Image

Use the following command to build a docker image:

make docker


You can define user specific settings in the file $ALEPHIUM_HOME/user.conf, where by default $ALEPHIUM_HOME points to ~/.alephium.


There are two kinds of tests:

  1. Unit tests and property based tests, which can be run with the make test command.
  2. Integration tests, which can be run with the make itest command.


Have a look at our contribution guide described in


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