Trusto Hybrid Biometric Blockchain Protocol
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Trusto Hybrid Biometric Blockcain (HBB) Protocol

The core library for running the Trusto transactions blockchain.

Trusto technology is a 2 layers block chain:

  • a transactions blockchain implemented by the HBB Protocol
  • a document blockchain implemented by the BDB Protocol

The structure of dual blockchains enables highspeed transactions (we aim at least 1500 trasactions per second) combined with high blockchain storage for documents. The 2 blockchains will be intimately linked with eachother, one will provice high speed transactions and the other high database storage in the blockchain.

The HBB Protocol library implements the basic low level functionality of the Trusto transactions block chain, like creating a block, creating a transaction, broadcasting a transaction into the network, connecting with other peers. It is independent from the document block chain (BDB) protocol. Also, provides functions for consensus protocol in the transactions blockchain.

The transactions validation is not a function of the HBB Protocol. The process of transactions validation is a function of the Hybrid Biomentrics Smart Contracts (HBS) library, because transactions are valid or not in terms of a smart contract execution. HBS library links together the two blockchains, the transactions and document blockchains.


The only supported installation method, right now, is from source files, stack.

Building from source


You will need to download and install stack.

You also need git to get the latest source code.

Get the source

git clone


To build the project, you need first to run stack setup. This command will make sure you have the correct haskell compiler, and, if you don't have it, it will download and install one in a separate location in such a way to not interract with your existing haskell environment (if you have one):

#> cd /the/location/of/trusto/hbb
#> stack setup

After the setup (you only need to run setup once) you may build, test or install the software. To build, simply issue:

#> stack build

To run the tests:

#> stack test

To install it in the stack's install directory, type:

#> stack install


Trusto hybrid bolckchain is a high speed blockchain aiming to provide more than 1500 transactions per second. To do this wee need to address 2 kind of problems:

  • the consensus validation speed
  • the block size

We address the consensus validation speed by using a mixed PoW-PoS consensus protocol. The miners will mine blocks using a classic proof of work algorithm. For each mined block, the network will generate and sign 100 PoS blocks.

So, there will be 2 kind of blocks:

  • mined blocks obtained by a classic PoW system
  • generated blocks, generated and signed by a PoS system

Mined blocks will not contain transactions. They will contain and, thus, sign the previously generated blocks. The generated blocks will contain transactions. Generated blocks, to be valid, must be included in a mined block. The generated blocks are broadcast to the network. Other nodes sign the generated block. They also can generate a new block with linking to the signed block and broadcast both into the network. This will form a generated chain. The longest generated chain is the winner chain and will be used for the next mined block.

When a new block is mined, the generated chain will start from zero. Since the root of generated chains is always a mined block, only the chains having as root the newest mined block are valid for generation, the others should be dropped by the network.

The size of blocks is an important issue, because we need the blocks to move fast between the nodes in order to achieve highe speed transactions. For this reason, transactions will only contain hashes for the actual transaction data. The transaction data will be stored in the docuement blockchain, and will be able to contain complex validation rules, discussed in the trusto hybrid biometric smart contract (HBS) library.