The Quantum Resistant Ledger (QRL) project is a public blockchain ledger specifically designed in anticipation of advancements in quantum computing (QC). Unlike existing ledgers, such as Bitcoin or Ethereum, QRL is dedicated to using a post-quantum secure signature for XMSS (eXtended Merkle Signature Scheme) transactions.

QRL also employs a low-power Proof of Stake (PoS) algorithm that again utilizes iterated hash chains and a verifiable hash-based pseudorandom function. The PoS algorithm is designed to be independent of traditional signatures, which are vulnerable to sufficiently powerful QC, and allows nodes to run on low-power devices like Raspberry Pis or laptops while passively earning rewards through staking.

Several cryptographic systems are considered quantum-resistant: hash-based cryptography, code-based cryptography, lattice-based cryptography, multivariate quadratic equations cryptography, and symmetric-key cryptography. Given a sufficient key size, all these schemes are believed to resist attacks from both classical and quantum computing.

Forward-secure hash-based digital signature schemes have minimal security requirements, relying solely on the collision-resistance of cryptographic hash functions. Changing the selected hash function generates a new hash-based digital signature scheme. Hash-based digital signatures are well-researched and are leading candidates for future post-quantum signatures. As such, they are the post-quantum signature class chosen by QRL.