Quantum — Where the Spinning Coin lands matters
TL;DR
This article is by our CEO and co-founder Kenneth Kinsella, where he talks about the looming reality of Quantum Day (Q-day) and why the “quantum threat” narrative is upside down. While most focus on the risks to blockchain, Ken argues that DeFi is actually better equipped to pivot via transparent protocol upgrades. In contrast, TradFi faces a much deeper crisis due to 40 years of accumulated “cryptographic debt,” fragmented legacy systems, and the “harvest now, decrypt later” threat that puts the entire authentication fabric of global finance at risk.
Richard Feynman once joked at the start of a quantum mechanics course that he was the only person who didn’t understand the subject, and that by the end, he hoped nobody would.
Quantum computing still feels like this. Our intuition lags far behind the maths. Qubits are like spinning coins, “heads and tails at once” until they land.
I use the spinning coin as a mental model for a quantum state. It’s in a condition where there is not one outcome but a superposition of possibilities that collapses only when observed. What if we applied that world of probabilities to finance, where almost all of today’s security assumptions rest on classical computers that cannot see “inside” those spinning coins?
Everyone talks about “the quantum threat to blockchain” as if Satoshi Nakamoto personally offended Schrödinger. The uncomfortable truth is that quantum computing is a far bigger problem for traditional finance than it is for blockchain. Quantum computers do not care whether a key protects a token wallet, a SWIFT message, a core banking mainframe, or a Visa HSM. They attack the mathematics under all of it, namely the public key cryptography that lets systems prove identity and the validity of a transaction. Break that, and you undermine the very authentication fabric of global finance.
Blockchain’s quantum problems are simpler. Most major chains rely on a small, well-understood set of algorithms and a relatively clean surface area of signatures, consensus, and a few key serialization formats. The path ahead is clear. You hard or soft fork to post-quantum schemes, provide migration paths for existing keys, and give users tools to move funds safely. Although politically and operationally painful, this will be a coordinated refit of a single, well-specified machine.
TradFi has a world of disparate machines and a patchwork of technology stacks. Start at the top with mobile banking apps and trading front ends, then dig down into API gateways, message buses, market data feeds, back-office systems, card switches, custody platforms, RTGS connections, SWIFT interfaces, mainframes running COBOL from the 1980s, and vendor appliances whose documentation no one has read in a decade. It just keeps going.
Each layer uses cryptography slightly differently. Each is on a different upgrade cycle, owned by a different team, often in a different legal entity and jurisdiction. Some are outsourced, others are “don’t you dare touch that” legacy boxes that only one engineer in Frankfurt still understands. If quantum breaks those public-key schemes, that entire stack becomes suspect at once.
This challenge is not only forward-looking. Sensitive financial data — payment messages, deal docs, customer records, trading strategies — is already stored in encrypted archives all over the world. A sufficiently powerful quantum adversary does not need to be inside your network on the day quantum breaks current cryptography (a.k.a. Qday). It just needs a tape backup from 2024 or 1984. The attack surface is not your shiny new cloud microservice but the last 40 years of accumulated cryptographic debt.
DeFi’s on‑chain state is public by design. There is less to “decrypt later,” and more to protect going forward. If quantum breaks signature schemes, the worst scenario is instantly visible in forged transactions, drained wallets, consensus chaos.
Because you know where the failures will show up, you can design explicit emergency responses like the recent quantum‑resistant wallet‑rescue prototypes announced by Lightning Lab’s CTO. In TradFi, no one is quite sure which systems in a global bank rely on vulnerable key‑exchange or signature schemes. You cannot patch what you cannot see, and you cannot coordinate a global cryptographic migration when your dependency graph lives in a thousand unmaintained spreadsheets.
This is exacerbated by a cultural gap. Blockchain assumes adversaries and improves and updates quickly and without requiring a full refit. Protocol changes happen in public, with explicit threat model review. When someone ships a quantum-resistant prototype, it is debated in the open, forked on GitHub, and attacked on testnets. The ecosystem expects drama around key management and consensus.
TradFi does security by process, by perimeter, by regulation, by “we passed the audit.” It doesn’t take quantum seriously as an impending failure of the mathematical guarantees that underpin every balance, trade, and payment. It’s politely regarded as an “emerging technology,” as though it won’t someday threaten the entire underlying cryptography.
The “quantum threatens blockchain” narrative is upside down. DeFi is less than a percent of global finance. If quantum breaks elliptic‑curve cryptography tomorrow, the real story will be total confusion in core banking, settlement failures, frozen payment rails, and a scramble among institutions to prove that their records and their counterparties’ can still be trusted.
Fixing blockchain is a bit like refitting a fleet of oil tankers — expensive, complex, and public, but technically contained. Fixing TradFi is like reinforcing every bridge and tunnel in the world after discovering the steel specification was wrong but without being allowed to divert traffic.
Can the 99‑plus percent of finance that falls under TradFi move with the same urgency and coherence that we expect from a protocol upgrade? Citigroup called this a “trillion dollar threat” in their January 2026 announcement. The immediate impact of Qday will be exacerbated by extended “harvest now, decrypt later” attacks, where data is stolen today and decrypted years from now.
There is serious pre-quantum work happening in standards bodies and central banks, but it’s restricted to consultation papers and research reports rather than public prototypes and high drama GitHub discussions. Still, this can be done right. The spinning quantum coin doesn’t have to land on “crisis.”
Picture that coin again — not quite heads, not quite tails, every possibility in play until it hits the table. If the coin lands the wrong way for crypto, a protocol forks and some token holders and positions get repriced. If it lands the wrong way for TradFi, the institutions that define money, credit, and trust suddenly must ask whether their own ledgers can still be believed.
Considering the years of quibbling over whether blockchain is critical infrastructure or a sideshow, it would be amusing if quantum risk was what finally pushed regulators, banks, and builders to deploy quantum-safe, blockchain based rails together. No one can afford, after all, to bet the whole system on a spinning coin.
About BABB Group
BABB Group Ltd is a UK-based fintech making on-chain finance more accessible and secure. Combining traditional finance with blockchain innovation, BABB Group provides institutionally-trusted and fully compliant digital asset management and peer-to-peer financial services. The Group encompasses two pillars: BABB, an e-money app, and ReDeFi, the underlying Layer 1 and 2 enterprise-grade blockchain infrastructure. This enables banks and financial institutions to mirror, move, and settle tokenised fiat deposits while maintaining regulatory-grade compliance, security, and auditability. BABB Group is bridging traditional finance and blockchain to make on-chain money practical at scale.
For more information, visit getbabb.com
About Kenneth Kinsella
Kenneth Kinsella is the CEO and Co-Founder of BABB Group, the UK-based fintech merging traditional finance with blockchain innovation. For the last three decades, Kinsella has worked around the world in executive-level roles, including global corporate development, transactional execution, and corporate finance for companies. He co-founded his first private equity company in 2005 and has raised over $500M+ in capital. His previous venture, Baobab Capital, focused on infrastructure development in West Africa. Kinsella has scaled multiple technology ventures and served on the executive boards and C-suites of major public and private organisations. Educated at Trinity College and a Fellow of The Institute of Chartered Accountants in England & Wales, Ken now lives and works in the UK.
