Posts Tagged ‘cryptography

How to encrypt a message in the afterglow of the big bang

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If you’ve got a secret to keep safe, look to the skies. Physicists have proposed using the afterglow of the big bang to make encryption keys.

The security of many encryption methods relies on generating large random numbers to act as keys to encrypt or decipher information. Computers can spawn these keys with certain algorithms, but they aren’t truly random, so another computer armed with the same algorithm could potentially duplicate the key.

An alternative is to rely on physical randomness, like the thermal noise on a chip or the timing of a user’s keystrokes.

Now Jeffrey Lee and Gerald Cleaver at Baylor University in Waco, Texas, have taken that to the ultimate extreme by looking at the cosmic microwave background (CMB), the thermal radiation left over from the big bang. Read the rest of this entry »

Written by physicsgg

November 30, 2015 at 12:44 pm

Quantum cryptography done on standard broadband fibre

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Thousands of kilometres of existing fibre may be used to carry quantum codes

By Jason Palmer
The “uncrackable codes” made by exploiting the branch of physics called quantum mechanics have been sent down kilometres of standard broadband fibre.

This “quantum key distribution” has until now needed a dedicated fibre separate from that used to carry data.

The technique, reported in Physical Review X, shows how to unpick normal data streams from the much fainter, more delicate quantum signal.

It may see the current best encryption used in many businesses and even homes.

The quantum key distribution or QKD idea is based on the sharing of a key between two parties – a small string of data that can be used as the basis for encoding much larger amounts.

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Certainly in a corporate environment it’s already affordable, and as time goes on I’m sure we’ll see the technology get cheaper”

Andrew Shields
Toshiba Cambridge Research Centre
Tiny, faint pulses of laser light are used in a bid to make single photons – the fundamental units of light – with a given alignment, or polarisation. Two different polarisations can act like the 0s and 1s of normal digital data, forming a means to share a cryptographic key.

What makes it secure is that once single photons have been observed, they are irrevocably changed. An eavesdropper trying to intercept the key would be found out.

Sending these faint, delicate quantum keys has until now been done on dedicated, so-called “dark fibres”, with no other light signals present.

That is an inherently costly prospect for users who have to install or lease a separate fibre.

So researchers have been trying to work out how to pull off the trick using standard, “lit” fibres racing with data pulses of millions of photons.

Slice of time
Now Andrew Shields of Toshiba’s Cambridge Research Laboratory and his colleagues have hit on the solution: plucking the quantum key photons out of the fibre by only looking in a tiny slice of time.

Dr Shields and his team developed detectors fit to catch just one photon at a time, as well as a “gate” that opens for just a tenth of a billionth of a second – at just the time the quantum key signal photons arrive, one by one.

The team achieved megabit-per-second quantum key data rates, all the while gathering gigabit-per-second standard data.

“Trying to use such low-level signals over ‘lit fibre’ has been rather like trying to see the stars whilst staring at the Sun,” said computer security expert Alan Woodward from the University of Surrey.

“What these researchers have developed is to use a technique that rapidly switches between the various light sources using the fibre such that one source isn’t swamping the other,” he told BBC News.
Paul Townsend of University College Cork led research published in the New Journal of Physics in 2011 aiming to do the same trick over 10km of fibre – but the new work was carried out over 90km of fibre at data rates hundreds of times higher….

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Written by physicsgg

November 20, 2012 at 1:38 pm


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Chemists devise means to use bacteria to encode secret messages

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Fluorescence images of BL21(DE3)pLysE fluorescent strains after growth and induced FP expression by IPTG

In the endless search to develop newer and cooler ways to send messages between people without other’s intercepting them, chemists from Tufts University working together have figured out a way to use a strain of bacteria to encode a message on a paper-like material that can then later be de-coded by the receiver. Manuel Palacios and David Walta, along with their team describe in their paper published in the Proceedings of the National Academy of Sciences, how they did it.

Called Steganography by Printed Arrays of Microbes (SPAM), the process is pretty simple. The team first developed seven different strains of the E. coli bacteria that grow in different colors (when bathed in ultraviolet light). They then devised a simple coding scheme based on pairings of the colors to represent letters of the alphabet (and some symbols). Next, they applied the bacteria to a plate of agar (a gelatinous substance that serves as food for the bacteria) where they grew into their respective color types. Next, a sheet of a nitrocellulose type material (that looks pretty much like paper) was pressed over the plate of agar, imprinting it with the bacteria. The result was then dried, causing the coloring attribute to disappear, making it ready for possible placement into an envelope for posting. After some time passed, the paper-like material was pressed onto an agar plate and the bacteria grew once again into their coloring, revealing the coded message…… Read the rest of this entry »

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September 27, 2011 at 4:31 pm

Quantum Cryptography

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Classical versus quantum bit. (a) lassical bit: If we put the ball in a classical box, the color of the ball that pops out is the same as the color we put in. (b) Qubit: If we put the ball in a quantum box and open the wrong door, the color of the ball that comes out is random.

When information is transmitted in microscopic systems, such as single photons (single light particles) or atoms, its information carriers obey quantum rather than classical physics. This o ers many new possibilities for information processing, since it is possible to invent novel information processes prevented by classical physics. Quantum cryptography is the most mature technology in the new eld of quantum information processing. Unlike cryptographic techniques where the security is based on unproven mathematical assumptions, the security of quantum cryptography is based on the laws of physics. Today it is developed with an eye towards a future in which cracking of classical public-key ciphers might become practically feasible. For example, a quantum computer might one day be able to crack today’s codes….
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August 9, 2011 at 7:23 am


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Hackers steal quantum code

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A suitcase full of equipment used by the Singapore/Trondheim researchers to eavesdrop on a quantum-key exchange.

While in principle unbreakable, quantum cryptography is known to have weaknesses in practice. One shortcoming has now been graphically illustrated by physicists in Singapore and Norway, who have been able to copy a secret quantum key without revealing their presence to either sender or receiver. The researchers are now working to remove the loophole they have exposed.
Quantum cryptography involves encoding messages using a key that is rendered secret by a quantum-mechanical principle – that the act of measuring affects the system being measured. In one popular scheme, the sender “Alice” sends a key in the form of a series of polarized single photons to the receiver “Bob”. Alice polarizes each photon at random using either a horizontal–vertical polarizer or a polarizer with two diagonal axes. Bob detects each photon by also randomly selecting one of the two different polarizers.
If Bob happens to pick the same polarizer as Alice, then he will definitely measure the correct polarization of a given photon. Otherwise, as the uncertainty principle dictates, there is a 50% chance he will get it wrong. Once he has made all the measurements, Bob asks Alice over an open channel which polarizers she used for each photon and he only keeps the results for those measurements where he happened to pick the correct polarizer, and this series of results becomes the secret key….. Read the rest of this entry »

Written by physicsgg

June 18, 2011 at 9:00 am