Abstract
Since ancient times, steganography, the art of concealing information, has largely relied on secret inks as a tool for hiding messages. However, as the methods for detecting these inks improved, the use of simple and accessible chemicals as a means to secure communication was practically abolished. Here, we describe a method that enables one to conceal multiple different messages within the emission spectra of a unimolecular fluorescent sensor. Similar to secret inks, this molecular-scale messaging sensor (m-SMS) can be hidden on regular paper and the messages can be encoded or decoded within seconds using common chemicals, including commercial ingredients that can be obtained in grocery stores or pharmacies. Unlike with invisible inks, however, uncovering these messages by an unauthorized user is almost impossible because they are protected by three different defence mechanisms: steganography, cryptography and by entering a password, which are used to hide, encrypt or prevent access to the information, respectively.
Highlights
Since ancient times, steganography, the art of concealing information, has largely relied on secret inks as a tool for hiding messages
We show that this property distinguishes molecular-scale messaging sensor (m-SMS) from other types of fluorescent molecular sensors, and from other chemical security systems[4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41] by enabling it to function as a molecular cipher device that can convert distinct chemical structures into unique encryption keys
The structure of m-SMS (Fig. 1a) consists of a cis-amino proline scaffold that is appended with three spectrally overlapping fluorophores: fluorescein (Flu), sulforhodamine B and nile blue (NB), which serve as a fluorescence resonance energy transfer (FRET) donor1–acceptor1/donor2–acceptor[2] system, respectively
Summary
Steganography, the art of concealing information, has largely relied on secret inks as a tool for hiding messages. We show that m-SMS and/or the chemical ingredients can be concealed and delivered on plain letter paper and that the messages can be rapidly revealed using a low-cost, handheld spectrometer This makes the m-SMS technology similar to the ancient technology of invisible inks in terms of simplicity, accessibility and the ease by which different messages can be concealed and exposed using common chemicals from various locations and in a short time
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