Modern authentication and communication protocols increasingly use physical keys in lieu of conventional software-based keys for security. This shift is primarily driven by the ability to derive a unique, unforgeable signature from a physical key. The sole demonstration of an unforgeable key, thus far, has been through quantum key distribution, which suffers from limited communication distances and expensive infrastructure requirements. Here, we show a method for creating unclonable keys by molecular self-assembly of resonance energy transfer (RET) devices. It is infeasible to clone the RET-key due to the inability to characterize the key using current technology, the large number of input-output combinations per key, and the variation of the key's response with time. However, the manufacturer can produce multiple identical devices, which enables inexpensive, secure authentication and communication over classical channels, and thus any distance. Through a detailed experimental survey of the nanoscale keys, we demonstrate that legitimate users are successfully authenticated 99.48% of the time and the false-positives are only 0.39%, over two attempts. We estimate that a legitimate user would have a computational advantage of more than 10(340) years over an attacker. Our method enables the discovery of physical key based multiparty authentication and communication schemes that are both practical and possess unprecedented security.
Modern authentication and communication protocols increasingly use physical keys in lieu of conventional software-based keys for security. This shift is primarily driven by the ability to derive a unique, unforgeable signature from a physical key. The sole demonstration of an unforgeable key, thus far, has been through quantum key distribution, which suffers from limited communication distances and expensive infrastructure requirements. Here, we show a method for creating unclonable keys by molecular self-assembly of resonance energy transfer (RET) devices. It is infeasible to clone the RET-key due to the inability to characterize the key using current technology, the large number of input-output combinations per key, and the variation of the key's response with time. However, the manufacturer can produce multiple identical devices, which enables inexpensive, secure authentication and communication over classical channels, and thus any distance. Through a detailed experimental survey of the nanoscale keys, we demonstrate that legitimate users are successfully authenticated 99.48% of the time and the false-positives are only 0.39%, over two attempts. We estimate that a legitimate user would have a computational advantage of more than 10(340) years over an attacker. Our method enables the discovery of physical key based multiparty authentication and communication schemes that are both practical and possess unprecedented security.
FRET between pairs of fluorophores is widely used as a biological assay. However, the properties of larger fluorophore networks are poorly understood and their application space has not yet been fully explored. This dissertation introduces DNA self-assembled FÖrster Resonance Energy Transfer (FRET) networks that provide a unique optical output when probed by a series of light pulses. We create a Markov model of the FRET networks and analyze over 1200 time-resolved fluorescence measurements on 300 prototypical networks. Our results show that the optical responses of FRET networks are highly repeatable and minor variations between the FRET networks can be discriminated resulting in a total of 10375 unique responses. These results are used in the following breakthrough applications: 1. Unclonable Cryptographic Key for Secure Authentication and Communication Modern authentication protocols rely on an asymmetry in the effort required by a legitimate user and an adversary to accurately decrypt an encoded message. These protocols ensure that communication between legitimate users is possible in polynomial time using a private key but a user without access to the exact key cannot compute the function using a probabilistic polynomial-time algorithm. Private-key cryptographic techniques currently employ physical keys based on algorithmic one-way functions, which are conjectured mathematical objects that are easy to compute but difficult to invert. Well-known examples of such one-way functions include the RSA and the Rabin functions. Although algorithmic one-way functions are widely used for authentication, their reliance on computational difficulty to provide security implies that they are not protected against future advances in computational capacity or speed. Also, use of a highly parallel network of conventional computers could potentially reverse engineer a key from the challenge-response pairs used in past communications. The key may also be obtained by duplicating the device. Most of the current physical embodiments of algorithmic one-way functions come with a tamper resistant packaging but remain vulnerable to sophisticated attacks. We develop a RET based physical key to overcome the limitations of conventional security keys. The key exploits resonance energy transfer between a network of fluorophores placed on a nanostructure. The fluorophores provide a unique, unpredictable output when probed by a series of light pulses of specific wavelengths and delays. A critical advantage of the RET key over existing keys is that the manufacturing process allows two identical devices to be produced allowing us to exploit the advantages of symmetric key encryption, for the first time, without the need to physically transfer the device between the two communicating parties. It is infeasible to model, characterize or replicate our key using modern cryptographic attacks including unfettered physical access to the device. This is because of the difficulty in characterizing the nanoscale structure and the large number of challenge-response pairs achievable for each key. Atomic force microscopy and time -resolved fluorescence measurements are performed to characterize the nanoscale structures. From over 1200 measurements on 300 prototypical keys, we estimate that a legitimate user would have a computational advantage of 10340 years over an attacker even if the attacker uses all the computational resources available in the world. Thus, the computational advantage of our key ensures perfect theoretical security for the foreseeable future. We provide an authentication protocol for use of the key and demonstrate that legitimate users are successfully authenticated 99.48% of the time with two trials. 2. Multiplexed Fluorescence Sensor for Cancer Detection Fluorescence microscopy is one of the most widely used assays in biological systems. However, the technique suffers from limited multiplexing capability with previous attempts at detecting more than 11 fluorophores simultaneously resulting in barcodes that are too big for in vivo analysis, expensive and involve time-consuming detection schemes. Here, we introduce DNA self-assembled FRET networks that provide a unique, optical output when probed by a series of light pulses. Markov and entropy modeling of the nanoscale FRET sensors show that 125 fluorophores can be observed simultaneously. Furthermore, experimental analyses of over 1200 time-resolved fluorescence signatures show that the optical responses are repeatable 99.48% of the time and that minor variations between FRET networks can be discriminated resulting in a total of 10375 unique responses. This enormous increase in spatial information density enabled by FRET networks allowed us to identify molecular signatures in lung and breast cancer tumors. It is now known that the presence of aberrant DNA/RNA secondary structure in the regulatory regions of genes involved in cell proliferation, cells growth and apoptosis can lead to cancer. The FRET sensor we designed, self-assembles DNA probes labeled with acceptor fluorophores to the target DNA/RNA secondary structure forming an optical network. A DNA strand labeled with a donor fluorophore triplex binds to a unique sequence adjacent to the secondary structure. When the donor fluorophore is excited, the optical network results in a different optical signal based on the presence of the wild-type or the aberrant secondary structure, through which we identified lung and breast cancer cells with high specificity and over 99.9% repeatability. The small size of fluorophores results in molecular scale spatial resolution while the optical sensing mechanism enables in vitro and in vivo characterization of the structure at picosecond resolution.
Modern technology unintentionally provides resources that enable the trust of everyday interactions to be undermined. Some authentication schemes address this issue using devices that give a unique output in response to a challenge. These signatures are generated by hard-to-predict physical responses derived from structural characteristics, which lend themselves to two different architectures, known as unique objects (UNOs) and physically unclonable functions (PUFs). The classical design of UNOs and PUFs limits their size and, in some cases, their security. Here we show that quantum confinement lends itself to the provision of unique identities at the nanoscale, by using fluctuations in tunnelling measurements through quantum wells in resonant tunnelling diodes (RTDs). This provides an uncomplicated measurement of identity without conventional resource limitations whilst providing robust security. The confined energy levels are highly sensitive to the specific nanostructure within each RTD, resulting in a distinct tunnelling spectrum for every device, as they contain a unique and unpredictable structure that is presently impossible to clone. This new class of authentication device operates with minimal resources in simple electronic structures above room temperature.
Modern technology unintentionally provides resources that enable the trust of everyday interactions to be undermined. Some authentication schemes address this issue using devices that give a unique output in response to a challenge. These signatures are generated by hard-to-predict physical responses derived from structural characteristics, which lend themselves to two different architectures, known as unique objects (UNOs) and physically unclonable functions (PUFs). The classical design of UNOs and PUFs limits their size and, in some cases, their security. Here we show that quantum confinement lends itself to the provision of unique identities at the nanoscale, by using fluctuations in tunnelling measurements through quantum wells in resonant tunnelling diodes (RTDs). This provides an uncomplicated measurement of identity without conventional resource limitations whilst providing robust security. The confined energy levels are highly sensitive to the specific nanostructure within each RTD, resulting in a distinct tunnelling spectrum for every device, as they contain a unique and unpredictable structure that is presently impossible to clone. This new class of authentication device operates with minimal resources in simple electronic structures above room temperature.
The rapid development of technology has provided a wealth of resources enabling the trust of everyday interactions to be undermined. Authentication schemes aim to address this challenge by providing proof of identity. This can be achieved by using devices that, when challenged, give unique but reproducible responses. At present, these distinct signatures are commonly generated by physically unclonable functions, or PUFs. These devices provide a straightforward measurement of a physical characteristic of their structure that has inherent randomness, due to imperfections in the manufacturing process. These hard-to-predict physical responses can generate a unique identity that can be used for authentication without relying on the secrecy of stored data. However, the classical design of these devices limits both their size and security. Here we show that the extensively studied problematic fluctuations in the current-voltage measurements of resonant tunnelling diodes (RTDs) provide an uncomplicated, robust measurement that can function as a PUF without conventional resource limitations. This is possible due to quantum tunnelling within the RTD, and on account of these room temperature quantum effects, we term such devices QUFs - quantum unclonable functions. As a result of the current-voltage spectra being dependent on the atomic structure and composition of the nanostructure within the RTD, each device provides a high degree of uniqueness, whilst being impossible to clone or simulate, even with state-of-the-art technology. We have thus created PUF-like devices requiring the fewest resources which make use of quantum phenomena in a highly manufacturable electronic device operating at room temperature. Conventional spectral analysis techniques, when applied to our QUFs, will enable reliable generation of unpredictable unique identities which can be employed in advanced authentication systems.
The unrelenting advancement of modern technology has inadvertently allowed the production of counterfeit components to become increasingly cheaper and easier, undermining the trust of everyday interactions and communications. An emerging solution to this problem is the use of physically unclonable functions1 (PUFs) - physical devices with random characteristics locked into their structure at the point of fabrication. The application of a stimulus to these constructions results in a hard-to-predict response due to the interaction with the complex microstructure of the device. This response is then used as a 'fingerprint' that can be used for a given application. Among others, these include low-cost device identification and authentication, secure key generation and the binding of software to hardware platforms. However, traditional PUFs have various setbacks: they suffer from not being truly unclonable, are susceptible to sophisticated attacks and bear a risk of emulation and simulation. Here we show that quantum physics lends itself to the provision of unique identities in the form of fluctuations in measurements of resonant tunnelling diodes (RTDs) containing various nanostructures. An example of which is a quantum dot, shown in Fig. 1. This provides an uncomplicated measure of identity, without conventional resource limitations or vulnerabilities. The quantum tunnelling spectrum also shown in Fig. 1 is sensitive to the atomic structure within the RTD, with each device providing extreme uniqueness that is presently impossible to clone or simulate. This new class of authentication device, coined the quantum unclonable function (QUF)2, operate with the fewest resources in simple electronic structures operating above 300 K.
The rapid advances in quantum computing pressure the existing essential cryptographic algorithms. In this context, Quantum Key Distribution (QKD) has been proposed as a quantum safe solution for key distribution. However, current QKD systems require an authenticated classical channel which relies on pre-shared symmetric keys that are manually distributed and do not guarantee the identity of the hardware that hosts them. This paper proposes a novel scheme, the Physically Unclonable Quantum Key Distribution (PU-QKD) system, to intrinsically authenticate the communicating endpoints in QKD. The PU-QKD scheme leverages classical Physical Unclonable Functions (PUFs) to encode the data transmission in discrete variable QKD protocols (e.g., BB84). Our scheme maintains the information-theoretic security of QKD protocols by integrating the PUF as an additional layer. Authentication is bound to hardware, providing a robust fingerprint, while lower post-processing overhead increases key rates. Additionally, the proposed scheme is resilient against state-of-the-art PUF vulnerabilities, such as modeling attacks.