The encryption process is essential for ensuring data protection and privacy. However, breaking the encrypted data becomes feasible as computational power grows exponentially. This leads to insecure data transmission over a public channel. Quantum key distribution is a secure communication mechanism that allows shared parties to exchange encryption keys periodically. Furthermore, it has the ability to detect eavesdropping since the error level becomes higher when she attempts to access the communication channel. This paper studies and analysis the performance of the uplink quantum channel between the ground station and the high-altitude platform system (HAPS). In order to achieve optimal performance, the system parameters, such as modulation variance, receiver aperture, and zenith angle influence, are tuned with consideration to the effects of weather conditions and beam wandering. For a HAP at vertical altitude 20 km and with 20° zenith angle and 100 MHz pulse generation rate, a raw key rate of 57 Mb/s and 63 Mb/s is estimated for homodyne and heterodyne detection schemes, respectively.
The encryption process is essential for ensuring data protection and privacy. However, breaking the encrypted data becomes feasible as computational power grows exponentially. This leads to insecure data transmission over a public channel. Quantum key distribution is a secure communication mechanism that allows shared parties to exchange encryption keys periodically. Furthermore, it has the ability to detect eavesdropping since the error level becomes higher when she attempts to access the communication channel. This paper studies and analysis the performance of the uplink quantum channel between the ground station and the high-altitude platform system (HAPS). In order to achieve optimal performance, the system parameters, such as modulation variance, receiver aperture, and zenith angle influence, are tuned with consideration to the effects of weather conditions and beam wandering. For a HAP at vertical altitude 20 km and with 20° zenith angle and 100 MHz pulse generation rate, a raw key rate of 57 Mb/s and 63 Mb/s is estimated for homodyne and heterodyne detection schemes, respectively.
Abstract In the contemporary digital era, ensuring the security of sensitive data and communication is of paramount significance. Encryption methods have been widely employed to safeguard data transmission over public channels. However, the exponential growth in computational power has led to concerns regarding the potential vulnerability of encryption methods. Consequently, breaking encryption poses a significant threat to data privacy. In response to these challenges, the field of quantum cryptography has emerged as a promising solution, offering a fundamentally unbreakable approach to secure communication. One of the key advancements in quantum cryptography is quantum key distribution (QKD). This secure communication mechanism relies on the principles of quantum mechanics to generate encryption keys, enabling secure information exchange between parties. This paper focuses on analysis of the quantum channel between the optical ground station (OGS) and the high-altitude platform System (HAPS). The research involves a meticulous examination and optimization of various system parameters such as performance secret key rate (SKR), electronic noise, modulation variance, and zenith angle. Remarkably, the SKR for a HAPS operating at a vertical altitude of 20 km, with a zenith angle of 20 degrees and a pulse generation rate of 500 MHz, is approximately 84 Mb/s and 44.5 Mb/s for homodyne and heterodyne detection, respectively. This information highlights the potential of quantum cryptography in providing secure communication channels that are resilient to cryptographic attacks.
In the contemporary digital era, ensuring the security of sensitive data and communication is of paramount significance. Encryption methods have been widely employed to safeguard data transmission over public channels. However the exponential growth in computational power has led to concerns regarding the potential vulnerability of encryption methods. Consequently, breaking encryption poses a significant threat to data privacy. In response to these challenges, the field of quantum cryptography has emerged as a promising solution, offering a fundamentally unbreakable approach to secure communication. One of the key advancements in quantum cryptography is quantum key distribution (QKD). This secure communication mechanism relies on the principles of quantum mechanics to generate encryption keys, enabling secure information exchange between parties. This paper focuses on analysis of the quantum channel between the optical ground station (OGS) and the high-altitude platform System (HAPS). The research involves a meticulous examination and optimization of various system parameters such as performance secret key rate (SKR), electronic noise, modulation variance, and zenith angle. Remarkably, the SKR for a HAPS operating at a vertical altitude of 20 km, with a zenith angle of 20 degrees and a pulse generation rate of 500MHz, is approximately 84Mb/s and 44.5 Mb/s for homodyne and heterodyne detection, respectively. This information highlights the potential of quantum cryptography in providing secure communication channels that are resilient to cryptographic attacks.
Abstract High-altitude platforms (HAPs) offer enhanced channel transmissivity compared to satellite-based links for free-space continuous-variable quantum key distribution. However, the inherent non-stationarity of the atmospheric channel, dominated by turbulence-induced fading, poses significant challenges to link stability and the consistent maximization of the secret key rate (SKR). To address this, real-time dynamic optimization of system parameters is essential for adapting to channel fluctuations. This study establishes a comprehensive physical transmission model for HAP uplinks to elucidate the impact mechanisms of the initial beam waist and transmitter modulation variance on the SKR. We quantitatively evaluate the performance gains yielded by single-parameter independent optimization versus dual-parameter joint optimization strategies. while joint parameter optimization yields the theoretical performance upper bound, dynamic regulation of the modulation variance emerges as the decisive factor in improving the signal-to-noise ratio and maximizing the SKR. Given the high hardware complexity and response latency associated with adaptive optical zooming mechanisms, we demonstrate that the ‘modulation variance-only’ optimization strategy constitutes the optimal engineering solution. This approach achieves quasi-optimal performance comparable to the joint strategy while significantly reducing implementation complexity, providing a robust and feasible design paradigm for future HAP-based quantum networks.
This paper presents the feasibility study of deploying Quantum Key Distribution (QKD) from High Altitude Platforms (HAPs), as a way of securing future communications applications and services. The paper provides a thorough review of the state of the art HAP technologies and summarises the benefits that HAPs can bring to the QKD services. A detailed link budget analysis is presented in the paper to evaluate the feasibility of delivering QKD from stratospheric HAPs flying at 20 km altitude. The results show a generous link budget under most operating conditions which brings the possibility of using diverged beams, thereby simplifying the Pointing, Acquisition and Tracking (PAT) of the optical system on the HAPs and ground, potentially widening the range of future use cases where QKD could be a viable solution.
Abstract This paper presents the feasibility study of deploying quantum key distribution (QKD) from high altitude platforms (HAPs), as a way of securing future communications applications and services. The paper provides a thorough review of the state of the art HAP technologies and summarises the benefits that HAPs can bring to the QKD services. A detailed link budget analysis is presented in the paper to evaluate the feasibility of delivering QKD from stratospheric HAPs flying at 20 km altitude. The results show a generous link budget under most operating conditions which brings the possibility of using diverged beams, thereby simplifying the pointing, acquisition and tracking of the optical system on the HAPs and ground, potentially widening the range of future use cases where QKD could be a viable solution.
Quantum Key Distribution (QKD) has emerged as a fundamentally secure approach to communication in the era of quantum computing, offering protection against threats posed to classical cryptographic schemes such as RSA and Diffie-Hellman. This thesis presents a comprehensive performance analysis of satellite-based QKD protocols, focusing on both prepare-and-measure and entanglement-based schemes under realistic atmospheric and operational conditions. The study begins by introducing the theoretical foundations of quantum communication, including qubits, entanglement, and quantum entropy, and motivates the need for satellite-based QKD to overcome the distance limitations of fiber-based systems. Subsequently, the thesis evaluates four prominent QKD protocols-BB84, B92, BBM92, and E91-using a circular beam propagation model that incorporates atmospheric effects such as diffraction, turbulence, attenuation, and pointing errors, along with environmental noise contributions for uplink and downlink. Comparative numerical simulations reveal that protocol performance is strongly influenced by channel asymmetries, beam propagation characteristics, and noise, providing guidance on optimal protocol selection for low Earth orbit (LEO) satellite links. The research further investigates high-dimensional (HD) QKD protocols, specifically HD-BB84 and HD-Extended B92, using the elliptic-beam approximation to account for turbulence-induced distortions for both uplink and downlink. Simulations under vary ing system dimensions, weather conditions, and zenith angles demonstrate that HD-BB84 achieves higher key rates, superior noise tolerance, and more favorable probability distributions of the key rate compared to HD-Extended B92, highlighting the advantages of high-dimensional encoding for robust satellite-based QKD.