What major threat does Quantum Computing pose to blockchain technology?

The major threat that quantum computing poses to blockchain technology primarily stems from its potential to break current cryptographic algorithms. Most blockchains rely on cryptographic techniques such as public-key cryptography to secure transactions and ensure the integrity and confidentiality of data. Algorithms like RSA and ECC (Elliptic Curve Cryptography) are foundational to this security model.

Quantum computers utilize the principles of quantum mechanics to process information in ways that classical computers cannot. Specifically, they can execute certain algorithms, such as Shor's algorithm, much more efficiently than classical computers. This capability allows quantum computers to factor large integers and compute discrete logarithms dramatically faster, potentially compromising the security of widely used cryptographic systems. If these algorithms are broken, it could lead to unauthorized access to private keys and the manipulation of blockchain data, thereby undermining the trust and security on which blockchain technology depends.

In contrast, the other choices do not align with the implications of quantum computing for blockchain. Quantum computing does not inherently increase transaction speeds, enhance security, or allow for greater scalability; rather, its primary concern is the risk it poses to established cryptographic methods that secure blockchain networks.