Exploring the Physical World

How To Write Unbreakable Secret Messages With Common Household Chemicals

Forbes

,

Between shadowy hackers and powerful government agencies, keeping electronic communication private can sometimes feel like a losing battle. Now chemists have come up with a clever alternative that's a little old-fashioned. They describe in Nature Communications a way to encrypt and send short messages on paper using everyday chemicals as keys, although they admit its usefulness probably has limits.

Scientist

Shutterstock

The system that David Margulies and colleagues at the Weizmann Institute of Science in Israel devised uses a one-time pad encryption. That means the people sending and receiving the coded message have copies of the same key that lets them encode and decode the message. Without the key the message is nearly impossible to decipher.

Because the messages can be sent on paper, Margulies' group thinks their system might even be safer from prying eyes than digital encryption for some people, like activists or journalists.

An example of a simple key could be matching the letters of the alphabet to random numbers. Margulies developed a way to use chemicals as random number generators, letting his group encrypt short messages.

It’s based on the light that molecules emit when they’re excited by energy input. Each element and molecule produces a unique spectrum of light when you hit it with a laser pulse.

The Weizmann group built a molecule they call a molecular-scale messaging sensor (m-SMS). It’s designed as a sort of skeleton key that can bind to a very broad range of common chemicals from acids to metal ions to hydrocarbons.

When m-SMS binds with one of those common compounds, the molecule this reaction produces has a unique emission spectrum. That’s the key to Margulies’ method. If both the sender and receiver have m-SMS and agree on what chemical to combine it with—and have the lab equipment to read emission spectra—they can use their identical spectral measurements as keys for encoding and decoding a message.

Because they designed m-SMS to be flexible, the added chemical can be something you'd find in the medicine cabinet, under the kitchen sink or in the refrigerator. The group experimented with baking soda, a nasal spray, lemon juice, Diet Coke and Carlsberg beer. They note that medicines are particularly well-suited because they’re held to such high quality control standards.

Encryption

The steps of Margulies' encryption method. Credit: Margulies et al. Nature Communications

Here's how it works: the encoder first matches each letter of the message to a number within an assigned range. This part of the key is public. After measuring the emission spectrum of m-SMS combined with a known chemical, each letter is matched with a wavelength along the spectrum. The intensity of the emitted light at each of those points is added to the letter’s numeric value. String together those sums and you have a coded message.

On the other end, the recipient samples the spectrum of the same combination of m-SMS and a common chemical, and measures the light intensity at the agreed-upon wavelengths. Subtracting the intensity values from the coded values produces the numbers that represent the letters of the message.

To test its usefulness, Margulies' group asked ten volunteers with no training in the method to decode a message. All of them were able to do it.

Margulies thinks paper-based cryptography like this could be useful in an age when security agencies and hackers make electronic communication feel increasingly unsafe. Encryption experts aren’t totally convinced.

“I do think there is place for non-digital encryption, for ‘fringe purposes’ such as spies, activists etc,” Vinod Vaikuntanathan, a cryptography professor at MIT, said in an email, although he adds that he’s not certain this specific encryption will prove useful for those or other applications.

Caltech quantum encryption researcher Thomas Vidick agrees. “In principle it could be useful,” he said of the Margulies’ method in an email. “‘Digital’ cryptography is often broken. I expect the kind of cryptography described in the paper to have its flaws as well; it will not be perfectly secure. But it might be adapted to some uses.”

Exploring the Physical World

How To Write Unbreakable Secret Messages With Common Household Chemicals

Forbes • TAGS: Chemistry , Technology , Computers , Sensors , Security

Between shadowy hackers and powerful government agencies, keeping electronic communication private can sometimes feel like a losing battle. Now chemists have come up with a clever alternative that's a little old-fashioned. They describe in Nature Communications a way to encrypt and send short messages on paper using everyday chemicals as keys, although they admit its usefulness probably has limits.

Scientist

Shutterstock

The system that David Margulies and colleagues at the Weizmann Institute of Science in Israel devised uses a one-time pad encryption. That means the people sending and receiving the coded message have copies of the same key that lets them encode and decode the message. Without the key the message is nearly impossible to decipher.

Because the messages can be sent on paper, Margulies' group thinks their system might even be safer from prying eyes than digital encryption for some people, like activists or journalists.

An example of a simple key could be matching the letters of the alphabet to random numbers. Margulies developed a way to use chemicals as random number generators, letting his group encrypt short messages.

It’s based on the light that molecules emit when they’re excited by energy input. Each element and molecule produces a unique spectrum of light when you hit it with a laser pulse.

The Weizmann group built a molecule they call a molecular-scale messaging sensor (m-SMS). It’s designed as a sort of skeleton key that can bind to a very broad range of common chemicals from acids to metal ions to hydrocarbons.

When m-SMS binds with one of those common compounds, the molecule this reaction produces has a unique emission spectrum. That’s the key to Margulies’ method. If both the sender and receiver have m-SMS and agree on what chemical to combine it with—and have the lab equipment to read emission spectra—they can use their identical spectral measurements as keys for encoding and decoding a message.

Because they designed m-SMS to be flexible, the added chemical can be something you'd find in the medicine cabinet, under the kitchen sink or in the refrigerator. The group experimented with baking soda, a nasal spray, lemon juice, Diet Coke and Carlsberg beer. They note that medicines are particularly well-suited because they’re held to such high quality control standards.

Encryption

The steps of Margulies' encryption method. Credit: Margulies et al. Nature Communications

Here's how it works: the encoder first matches each letter of the message to a number within an assigned range. This part of the key is public. After measuring the emission spectrum of m-SMS combined with a known chemical, each letter is matched with a wavelength along the spectrum. The intensity of the emitted light at each of those points is added to the letter’s numeric value. String together those sums and you have a coded message.

On the other end, the recipient samples the spectrum of the same combination of m-SMS and a common chemical, and measures the light intensity at the agreed-upon wavelengths. Subtracting the intensity values from the coded values produces the numbers that represent the letters of the message.

To test its usefulness, Margulies' group asked ten volunteers with no training in the method to decode a message. All of them were able to do it.

Margulies thinks paper-based cryptography like this could be useful in an age when security agencies and hackers make electronic communication feel increasingly unsafe. Encryption experts aren’t totally convinced.

“I do think there is place for non-digital encryption, for ‘fringe purposes’ such as spies, activists etc,” Vinod Vaikuntanathan, a cryptography professor at MIT, said in an email, although he adds that he’s not certain this specific encryption will prove useful for those or other applications.

Caltech quantum encryption researcher Thomas Vidick agrees. “In principle it could be useful,” he said of the Margulies’ method in an email. “‘Digital’ cryptography is often broken. I expect the kind of cryptography described in the paper to have its flaws as well; it will not be perfectly secure. But it might be adapted to some uses.”