Sairam Jalakam Devarajulu, Blockchain Technology Expert, writes a special article for DM about the security challenges posed to Blockchain technology by the evolution of Quantum Computing.
Quantum computing, once considered theoretical, is rapidly becoming a real-world force. These machines leverage principles like superposition and entanglement to solve problems far beyond the reach of classical computers. One of the most critical vulnerabilities this technology exposes lies at the core of Bitcoin’s architecture: its reliance on elliptic-curve cryptography (ECDSA).
A sufficiently advanced quantum computer, equipped with Shor’s algorithm, could feasibly extract private keys from public ones, rendering Bitcoin wallets vulnerable to unauthorized access. While the technology is not yet at that level, experts caution that this threat is no longer speculative.
Cybersecurity researchers and analysts warn that ‘Q-Day’—the point when quantum computers can compromise widely used cryptographic algorithms—could arrive within the next decade. Forecasts from firms like Gartner suggest this could happen as early as 2029, with full compromise possible by 2034. Industry voices, including cybersecurity strategist David Carvalho, are urging immediate action, stressing that the window for preparation is narrowing.
Currently, an estimated 4 million bitcoins—about 25 to 30 percent of the total in circulation—are stored in addresses where public keys have already been exposed. These assets are particularly susceptible to a strategy known as “harvest now, decrypt later,” in which adversaries collect encrypted data today in hopes of breaking it with future quantum tools. Even dormant wallets from Bitcoin’s early days could be reactivated through quantum decryption, flooding the market and potentially destabilizing prices.
A successful quantum attack could unfold in real time. An attacker might intercept a transaction before it is confirmed on the blockchain, use quantum computing to extract the private key, and reroute the funds—all within seconds. Such a breach would not only result in direct theft but also shake the foundational trust in Bitcoin’s security, potentially sparking widespread panic and sell-offs.
To defend against this looming threat, Bitcoin must transition from ECDSA to quantum-resistant cryptographic algorithms. The U.S. National Institute of Standards and Technology (NIST) has identified viable post-quantum alternatives, including CRYSTALS-Dilithium, SPHINCS+, and Classic McEliece. However, implementing such changes requires a hard fork—a significant and coordinated upgrade to the Bitcoin network. Some models suggest up to 76 days of dual-protocol operation would be needed, demanding collaboration across developers, miners, exchanges, and wallet providers.
A concept known as ‘crypto-agility’ is also gaining traction. This approach emphasizes building systems capable of quickly adapting to new cryptographic methods in response to emerging threats. It is now viewed as a necessity rather than a theoretical safeguard.
Individual users can take steps to minimize risk. Avoiding address reuse, upgrading to modern wallets, and transitioning away from legacy formats such as Pay-to-PubKey (P2PK) or reused Pay-to-PubKey-Hash (P2PKH) can help safeguard holdings. Institutions have also taken notice—investment giants like BlackRock have formally acknowledged quantum computing as a material risk in Bitcoin-related regulatory filings.
Although a full-blown quantum threat may still be years away, the time to act is now. Data encrypted today may retain value for decades, making it an appealing target for future decryption. Governments and organizations are responding with policy and standards. For example, U.S. Executive Order 14144 mandates federal agencies to begin the shift toward quantum-safe cryptography.
Bitcoin’s cryptographic defenses remain intact today, but that security will not last indefinitely. The evolution of quantum technology is accelerating, and without a proactive transition to post-quantum cryptography, the risk to Bitcoin’s trust and value will only grow. The crypto community must act with urgency and coordination to secure the future of decentralized finance.