symmetric key

The advent of quantum computing poses a threat which could break open the security systems protecting the world’s financial data and transactions. 

Professor Michele Mosca

Protecting financial data has always been a cat-and-mouse game. What is different now is that the cat could be de-clawed. Quantum computing, a new form of computer processing, promises to break open the security systems that safeguard much of the world’s financial data and transactions.

Quantum computing is expected to be much more powerful than anything currently available because it does not rely on the binary digits 1 or 0 to represent data but exploits the fact that subatomic particles can exist in more than one state at once.

Experts cannot say with certainty when a fully-fledged quantum computer will exist but, once it does, public key encryption schemes in use today will be breakable. Quantum computer algorithms that can crack such schemes have already been put through their paces.

The good news is that cryptographic techniques resilient to quantum computers exist. And while such “quantum-safe” technologies still need to be constructed, security experts agree that financial institutions must prepare now for a quantum-computer world.

 

Experts cannot say with certainty when a fully-fledged quantum computer will exist but, once it does, public key encryption schemes in use today will be breakable

 

Ticking clock

There is a 50 percent chance that a quantum computer will exist by 2031, according to Professor Michele Mosca, co-founder of the Institute for Quantum Computing at the University of Waterloo, Canada, and of security company evolutionQ.

A one-in-two chance of a fully working quantum computer by 2031 suggests financial institutions have time to prepare, but that is not the case. Since financial companies are required to keep data confidential for many years, quantum-safe protocols need to be in place for the same length of time that confidentiality is mandated prior to quantum computing. So, for example, if data must be kept confidential for seven years, quantum-safe techniques need to be in place by 2024 at the latest. Otherwise, cyber criminals need only intercept and store RSA-encrypted data after 2024 and wait until 2031 to have a 50-50 chance of access to sensitive information.

Unsurprisingly, replacing public key infrastructure with quantum-safe technology is itself a multi-year project. First, the new systems must be tested and verified to ensure they meet existing requirements – not just that their implementation is secure but that their execution times for various applications are satisfactory. Then, all the public key infrastructure needs to be revamped – a considerable undertaking. This means that, if upgrading infrastructure takes five years, companies should be preparing if quantum computers arrive by 2031.

Professor Renato Renner, the head of the quantum information theory research group at ETH Zurich, the Swiss science and technology university, sees the potential for even more immediate risk. “Having a full-blown quantum computer is not necessarily what you need to break cryptosystems,” he says. In his view, financial companies should be worried that there are already early examples of quantum computers that are stronger than current computers. “It could well be that in five years we have already sufficiently powerful devices that can break RSA cryptosystems,” says Renner. 

Quantum-safe approaches

Quantum-safe technologies comprise two approaches, one based on maths and another that exploits the laws of physics.

The maths approach delivers new public key algorithms that are designed to be invulnerable to quantum computing, known as post-quantum or quantum-resistant techniques.

The US National Institute of Science and Technology is taking submissions for post-quantum algorithms with the goal of standardising a suite of protocols by the early to mid-2020s. These include lattice-based, coding-based, isogenies-based and hash-function-based schemes. The maths behind these schemes is complex but the key is that none of them is based on the multiplication of prime numbers and hence susceptible to factoring, which is what quantum computers excel at.

 

It could well be that in five years we have already sufficiently powerful devices that can break RSA cryptosystems

Nigel Smart, co-founder of Dyadic Security, a software-defined cryptography company, points out that companies are already experimenting with post-quantum lattice schemes. Earlier this year, Google used it in experimental versions of its Chrome browser when talking to its sites. “My betting is that lattice-based systems will win,” says Smart.

The other quantum-safe approach exploits the physics of the very small – quantum mechanics – to secure links so that an eavesdropper on the link cannot steal data. Here particles of light – photons – are used to send the key used to encrypt data (see Cryptosystems – two ways to secure data below) where each photon carries a digital bit of the key.

Financial and other companies that secure data should already be assessing the vulnerabilities of their security systems

Should an adversary eavesdrop with a photodetector and steal the photon, the photon will not arrive at the other end. Should the hacker be more sophisticated and try to measure the photon before sending it on, here they come up against the laws of physics where measuring a photon changes its parameters.

Given these physical properties of photons, the sender and receiver typically reserve at random a number of the key’s photons to detect a potential eavesdropper. If the receiver detects an altered photon, the change suggests the link is compromised.

But quantum key distribution only solves a particular class of problem – for example, protecting data sent across links such as a bank sending information to a data centre for back-up. Moreover, the distances a single photon can travel is a few tens of kilometres. If longer links are needed, intermediate trusted sites are required to regenerate the key, which is expensive and cumbersome.

The technique is also dependent on light and so is not as widely applicable as quantum-resistant techniques. “People are more interested in post-quantum cryptography,” claims Smart.

 

What now?

BT, working with Toshiba and ADVA Optical Networking, the optical transport equipment maker, has demonstrated a quantum-protected link operating at 100 gigabits-per-second.

What is missing still is a little bit more industrialisation,” says Andrew Lord, head of optical communications at BT. “Quantum physics is pretty sound but we still need to check that the way this is implemented, there are no ways of breaching it.”

Kelly Richdale

ID Quantique, the Swiss quantum-safe crypto technology company, supplied one early-adopter bank with its quantum key distribution system as far back as 2007. The bank uses a symmetric key scheme coupled with a quantum key.

“You can think of it as adding an additional layer of quantum security on top of everything you already have,” says Kelly Richdale, ID Quantique’s vice-president of quantum-safe security.

“Quantum key distribution has provable security. You know it will be safe against a quantum computer if implemented correctly,” she says. “With post-quantum algorithms, it is a race against time, since in the future there may be new quantum attacks that could render them as vulnerable as RSA.”

Andersen Cheng, chief executive of start-up PQ Solutions, a security company with products including secure communication using post-quantum technology, argues that both quantum- resistant and quantum key distribution will be needed. “You can use both but quantum key distribution on its own is not enough and it is expensive,” he says.

 

Most organisations do not have a detailed map of where all their information assets are and which business functions rely on which crypto algorithms

 

What next?

Mosca says that leading financial services companies are aware of the threat posed by quantum computing but their strategies vary: some point to more pressing priorities while others want to know what they can buy now to solve the problem.

He disagrees with both extreme approaches. Financial companies should, in his view, already be assessing the vulnerabilities of their systems. “Most organisations do not have a detailed map of where all their information assets are and which business functions rely on which crypto algorithms,” he says.

Companies should also plan for their systems to change a lot over the next decade. That is why it is premature to settle on a solution now since it will probably need upgrading. And they must test quantum-resistant algorithms. “We don’t have a winner yet,” says Mosca.

Most importantly, financial institutions cannot afford to delay. “Do you really want to be in the catch-up game and hope someone else will solve the problem for you?” asks Mosca.

The article first appeared in the June-July issue of the Financial World, the journal of The London Institute of Banking & Finance, published six times per year in association with the Centre for The Study of Financial Innovation (CSFI).

 

Cryptosystems – two ways to secure data

To secure data, special digital “keys” are used to scramble the information. Two encryption schemes are used – based on asymmetric and symmetric keys.

Public key cryptography that uses a public and private key pair is an example of an asymmetric scheme. The public key, as implied by the name, is published with the user’s name. Any party wanting to send data securely to the user employs the published public key to scramble the data. Only the recipient, with the associated private key, can decode the sent data. The RSA algorithm is a widely used example. (RSA stands for the initials of the developers: Ron Rivest, Adi Shamir and Leonard Adleman.) A benefit of public key cryptography is that it can be used as a digital signature scheme as well as for protecting data. The downside is that it requires a lot of processing power and is slow even then.

Symmetric schemes, in contrast, are much less demanding to run and use the same key at both link ends to lock and unlock the data. A well-known symmetric key algorithm is the Advanced Encryption Standard, which uses keys up to 256-bits long (AES-256); the more bits, the more secure the encryption.

The issue with the symmetrical scheme is getting the secret key to the recipient without it being compromised. One way is to send a security guard handcuffed to a locked case. A more digital-age approach is to send the secret key over a secure link. Here, public key cryptography can be used; the asymmetric key scheme can be employed to protect the symmetric key transmission prior to secure symmetric communication.

Quantum computing is a potent threat because it undermines both schemes when existing public key cryptography is involved.