Major Cryptocurrencies Unprepared for Quantum Threat

Most cryptocurrencies are not prepared for the threat of quantum computers, which could potentially break their security. Almost all major chains use elliptic curve mathematics to secure transactions, and these schemes can be broken by a large quantum computer using Shor's algorithm.

The shared foundation of cryptography across most chains means that a cryptographically relevant quantum computer would not threaten one coin in isolation, but rather the signature scheme underneath most of the market at once. This is known as Q-Day.

Only one major chain, the Quantum Resistant Ledger (QRL), has implemented a genuinely quantum-resistant cryptocurrency from day one. Since its 2018 mainnet, it has signed every transaction with XMSS, a hash-based signature scheme that rests on the security of hash functions rather than elliptic curves.

Many major chains have roadmaps for post-quantum cryptography, but these are often years away from implementation. Bitcoin, Ethereum, XRP, Cardano, Hedera, and Polkadot all have plans to transition to quantum-resistant signatures, but none have implemented them yet. Some chains, like Solana and Algorand, offer opt-in tools that allow users to use quantum-resistant signatures, but these are not protocol-wide changes.

Litecoin has no funded effort to migrate to post-quantum cryptography, Monero is still in the research stage, and IOTA actually removed its original quantum resistance in 2021. The clock is ticking for all chains, with expert timelines clustering in the early 2030s.