Citi issued a report this week warning that accelerating advances in quantum computing are compressing the timeline for risks to cryptocurrency and broader internet infrastructure. Bitcoin, the bank's analysts said, is seen as particularly exposed.
Quantum timeline tightens
The report does not peg a specific year when a cryptographically relevant quantum machine will arrive. But it states clearly that the window for preparing defenses is narrowing faster than many in the industry assume. Citi points to recent breakthroughs in qubit stability and error correction as evidence that the long-dreaded threat is no longer a distant hypothetical.
That changes the math for any system that relies on public-key cryptography — which is essentially all of modern internet security, and certainly Bitcoin.
Bitcoin's exposure
Bitcoin's security model depends on elliptic curve digital signatures (ECDSA) to authorize transactions and SHA-256 for mining. A sufficiently powerful quantum computer could theoretically break ECDSA, allowing an attacker to derive private keys from public ones. Citi's report singles out Bitcoin because of its enormous market value and the irreversible nature of its transactions. Once coins are stolen, there's no chargeback.
The bank also notes that Bitcoin's decentralized upgrade process makes it harder to implement a quick fix compared to centralized systems. That governance friction adds to the risk.
Beyond crypto
The report doesn't limit its warning to digital currencies. It says the same quantum advances threaten TLS encryption, VPNs, and virtually all internet infrastructure that depends on RSA or elliptic curve cryptography. A quantum computer capable of breaking Bitcoin would also break the secure sockets layer that protects online banking, email, and government communications.
Citi's analysis adds that the financial sector — including the bank itself — needs to accelerate migration to post-quantum cryptographic standards before the window slams shut.
The report arrives as global standards bodies like NIST are finalizing post-quantum algorithms, but adoption across the crypto industry remains slow. For Bitcoin and the broader internet, the clock is ticking.
