New breakthrough enables perfectly secure digital communications using steganography

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"Working in close collaboration with Carnegie Mellon University, the researchers developed a new method which they envisage may soon be used widely in digital human communications, including social media and private messaging. In particular, the ability to send perfectly secure information may empower vulnerable groups, such as dissidents, investigative journalists, and humanitarian aid workers.

The algorithm applies to a setting called steganography: the practice of hiding sensitive information inside of innocuous content. Steganography differs from cryptography because the sensitive information is concealed in such a way that this obscures the fact that something has been hidden. An example could be hiding a Shakespeare poem inside an AI-generated image of a cat.

Despite having been studied for more than 25 years, existing steganography approaches generally have imperfect security, meaning that individuals who use these methods risk being detected. This is because previous steganography algorithms would subtly change the distribution of the innocuous content.

To overcome this, the research team used recent breakthroughs in information theory, specifically minimum entropy coupling, which allows one to join two distributions of data together such that their mutual information is maximised, but the individual distributions are preserved.

As a result, with the new algorithm, there is no statistical difference between the distribution of the innocuous content and the distribution of content that encodes sensitive information. ...
The research team has filed a patent for the algorithm, but intend to issue it under a free licence to third parties for non-commercial responsible use. This includes academic and humanitarian use, and trusted third-party security audits. ..."

New breakthrough enables perfectly secure digital communications | University of Oxford A team led by University of Oxford researchers has achieved a breakthrough in secure communications by developing an algorithm that conceals sensitive information so effectively that it is impossible to detect that anything has been hidden.

Perfectly Secure Steganography Using Minimum Entropy Coupling (preprint, open access)

A conceptual illustration of generative steganographic visual secret sharing schemes. Here, an image of a treasure map is hidden within an image of a cat. The treasure map can be extracted from the cat image, for instance by entering a password. The cat image itself looks entirely unsuspicious, thus providing plausible deniability to users.