  This paper describes the work carried out by the Inter-American Development
Bank, the IDB Lab, LACChain, Cambridge Quantum Computing (CQC), and Tecnologico
de Monterrey to identify and eliminate quantum threats in blockchain networks.
  The advent of quantum computing threatens internet protocols and blockchain
networks because they utilize non-quantum resistant cryptographic algorithms.
When quantum computers become robust enough to run Shor's algorithm on a large
scale, the most used asymmetric algorithms, utilized for digital signatures and
message encryption, such as RSA, (EC)DSA, and (EC)DH, will be no longer secure.
Quantum computers will be able to break them within a short period of time.
Similarly, Grover's algorithm concedes a quadratic advantage for mining blocks
in certain consensus protocols such as proof of work.
  Today, there are hundreds of billions of dollars denominated in
cryptocurrencies that rely on blockchain ledgers as well as the thousands of
blockchain-based applications storing value in blockchain networks.
Cryptocurrencies and blockchain-based applications require solutions that
guarantee quantum resistance in order to preserve the integrity of data and
assets in their public and immutable ledgers. We have designed and developed a
layer-two solution to secure the exchange of information between blockchain
nodes over the internet and introduced a second signature in transactions using
post-quantum keys. Our versatile solution can be applied to any blockchain
network. In our implementation, quantum entropy was provided via the IronBridge
Platform from CQC and we used LACChain Besu as the blockchain network.
