Fidelity Digital Assets says Bitcoin could eventually be upgraded against quantum-computing attacks, although the change would require broad coordination across the network. Bitcoin transactions generally use ECDSA or Schnorr signatures, whose underlying mathematical problem could theoretically be reversed by a sufficiently powerful quantum computer running Shor’s algorithm. Such machines do not yet exist. The report examines SHRINCS, a proposed hash-based system with stateful and stateless signature options. Its current draft specifies a 48-byte public key, stateful signatures of 548 to 4,619 bytes and a 5,777-byte stateless fallback based on NIST’s SLH-DSA standard. Larger signatures would consume more blockchain space, potentially raising fees and reducing transaction throughput during periods of high demand, although the effect may be smaller while Bitcoin’s mempool is nearly empty. Implementing the change would require new consensus rules, likely through a backward-compatible soft fork, supported by wallet makers, miners, exchanges, node operators and users. In July, Fidelity and eight other financial and crypto firms funded a $15 million Bitcoin security initiative that includes research into quantum-resistant solutions.