51动漫

A COMPUTER that doesn鈥檛 even exist yet is already giving cryptographers sleepless nights.

Encryption experts at Hewlett-Packard鈥檚 British research lab in Bristol are calling on colleagues around the world to develop systems that will render today鈥檚 encrypted data immune to code-breaking attacks from quantum computers.

HP researchers Keith Harrison and Bill Munro predict that quantum computers will become a reality within 10 to 15 years. These machines pose a security threat because their ability to perform many calculations at once means they will be able to uncover the encryption keys that are, for practical purposes, uncrackable by today鈥檚 鈥榗lassical鈥� conventional computers.

If that happens, people will be able to tap into private cellphone calls, and secure e-commerce will be a thing of the past. 鈥淔or ten years things are safe, but in 20 years I鈥檓 not so sure,鈥� Munro told 51动漫.

Quantum computing engineers are already on the offensive, developing algorithms that will allow quantum computers to calculate at enormous speeds. One, called Shor鈥檚 algorithm, speeds up the process of finding factors of very large numbers 鈥� a basic requirement in code breaking.

Now HP is planning workshops to develop countermeasures. 鈥淧art of the problem is that we don鈥檛 yet know which way to look,鈥� says Munro.

One solution, the HP researchers suggest, might be to develop new forms of cryptography that are impervious to the kind of attack quantum computers will be capable of.

But Harrison says that new mathematical tricks probably won鈥檛 work, because the more mathematical the function, the easier it seems to be for quantum computers to break it. But it takes a long time to develop new encryption algorithms, let alone quantum-immune ones. And once that has been achieved it can take more than a decade for a new algorithm to be adopted.

A quantum computer can represent a 0 and a 1 at the same time in a quantum bit (called a qubit), and it鈥檚 this that will allow such machines to perform many different calculations at once, and arrive at answers so fast.

These machines will need a qubit for every bit in a key they are trying to break. So one strategy to make 鈥渜uantum-proof鈥� codes might be to a use cryptographic keys that are longer than the number of qubits quantum computers will have in the foreseeable future.

The trouble is that every time you double the key size, the code takes six times as long to process on a classical computer. 鈥淓ven if it鈥檚 quantum-immune it still has to be a good classical cryptographic tool,鈥� says Munro.

Some crypto experts doubt whether HP鈥檚 call to arms is even necessary. 鈥淚t鈥檚 a fascinating research problem, but I don鈥檛 think it鈥檚 going to be pressing in my lifetime,鈥� says 35-year-old Nicko van Someren of British-based cryptography company nCipher in Cambridge. 鈥淎nd I expect to live a long time.鈥�