Automatic Link Establishment Research Articles

Research and development of an algorithm for automatic link establishment in the shortwave range

Research and development of an algorithm for automatic link establishment in the shortwave range

Cryptanalysis of HALFLOOP Block Ciphers

HALFLOOP is a family of tweakable block ciphers that are used for encrypting automatic link establishment (ALE) messages in high frequency radio, a technology commonly used by the military, other government agencies and industries which require high robustness in long-distance communications. Recently, it was shown in [DDLS22] that the smallest version of the cipher, HALFLOOP-24, can be attacked within a practical time and memory complexity. However, in the real-word ALE setting, it turns out that this attack require to wait more than 500 years to collect the necessary amount of plaintext-tweak-ciphertext pairs fulfilling the conditions of the attack.In this paper, we present real-world practical attacks against HALFLOOP-24 which are based on a probability-one differential distinguisher. In our attacks, we significantly reduce the data complexity to three differential pairs in the chosen-plaintext (CPA) setting which is optimal in the sense that even a brute force attack needs at least six plaintext-tweak-ciphertext pairs to uniquely identify the correct key. Considering the same ALE setting as [DDLS22], this translates to a reduction from 541 years to 2 hours worth of intercepted traffic.Besides, we provide the first, non generic, public cryptanalysis of HALFLOOP-48 and HALFLOOP-96. More precisely, we present Demirci-Selçuk meet-in-the-middle attacks against full-round HALFLOOP-48 and round-reduced HALFLOOP-96 to recover the complete master key in a CPA setting. However, unlike the attacks on HALFLOOP-24, our attacks on the larger versions are only theoretical. Moreover for HALFLOOP-96 the known generic time-memory trade-off attack, based on a flawed tweak handling, remains the strongest attack vector.In conclusion, we iterate what was already stated in [DDLS22]: HALFLOOP does not provide adequate protection and should not be used.

Breaking HALFLOOP-24

HALFLOOP-24 is a tweakable block cipher that is used to protect automatic link establishment messages in high frequency radio, a technology commonly used by government agencies and industries that need highly robust long-distance communications. We present the first public cryptanalysis of HALFLOOP-24 and show that HALFLOOP-24, despite its key size of 128 bits, is far from providing 128 bit security. More precisely, we give attacks for ciphertext-only, known-plaintext, chosen-plaintext and chosen-ciphertext scenarios. In terms of their complexities, most of them can be considered practical. However, in the real world, the amount of available data is too low for our attacks to work. Our strongest attack, a boomerang key-recovery, finds the first round key with less than 210 encryption and decryption queries. In conclusion, we strongly advise against using HALFLOOP-24.

Improving the Performance of HF Radio Networks in the Presence of Interference through Automatic Link Establishment with Frequency Hopping Technique

Improving the Performance of HF Radio Networks in the Presence of Interference through Automatic Link Establishment with Frequency Hopping Technique

Cryptanalysis of the SoDark Cipher for HF Radio Automatic Link Establishment

The SoDark cipher is used to protect transmitted frames in the second and third generation automatic link establishment (ALE) standards for high frequency (HF) radios. The cipher is primarily meant to prevent unauthorized linking and attacks on the availability of HF radio networks. This paper represents the first known security analysis of the cipher used by the second generation ALE protocol—the de facto world standard—and presents a related-tweak attack on the full eight round version of the algorithm. Under certain conditions, collisions of intermediate states several rounds into the cipher can be detected from the ciphertext with high probability. This enables testing against the intermediate states using only parts of the key. The best attack is a chosen-ciphertext attack which can recover the secret key in about an hour with 100% probability, using 29 chosen ciphertexts.

Recognizing Automatic Link Establishment Behaviors of a Short-Wave Radio Station by an Improved Unidimensional DenseNet

It is difficult to recognize Automatic Link Establishment (ALE) behaviors of a short-wave radio station, if we do not acquire the radio station's communication protocol standard. A method is proposed to recognize different ALE behaviors by using an improved unidimensional DenseNet. In this work, we directly recognize ALE signals in physical layer without the radio station's communication protocol standard. Hence, we can avoid difficulties in demodulation, decryption and so on. Actually, the original DenseNet is used extensively in the field of computer vision, so the original DenseNet is firstly adapted for the unidimensional input. And then, two parallel dense blocks are used in our improved unidimensional DenseNet, which could improve the capability of network to extract ALE signals' deep features. The experimental results show that the proposed method is able to recognize different ALE behaviors of a short-wave radio station. And improved DenseNet has better recognition performance than simple DenseNet. The simple DenseNet only contains one dense block. Finally, the results of comparison experiments also show that some classic networks have worse performance in ALE behaviors recognition, such as LeNet-5, ResNet-34, and DenseNet-121.

A heterogeneous information fusion deep reinforcement learning for intelligent frequency selection of HF communication

The high-frequency(HF) communication is one of essential communication methods for military and emergency application. However, the selection of communication frequency channel is always a difficult problem as the crowded spectrum, the time-varying channels, and the malicious intelligent jamming. The existing frequency hopping, automatic link establishment and some new anti-jamming technologies can not completely solve the above problems. In this article, we adopt deep reinforcement learning to solve this intractable challenge. First, the combination of the spectrum state and the channel gain state is defined as the complex environmental state, and the Markov characteristic of defined state is analyzed and proved. Then, considering that the spectrum state and channel gain state are heterogeneous information, a new deep Q network (DQN) framework is designed, which contains multiple sub-networks to process different kinds of information. Finally, aiming to improve the learning speed and efficiency, the optimization targets of corresponding sub-networks are reasonably designed, and a heterogeneous information fusion deep reinforcement learning (HIF-DRL) algorithm is designed for the specific frequency selection. Simulation results show that the proposed algorithm performs well in channel prediction, jamming avoidance and frequency channel selection.

Deep spectrum prediction in high frequency communication based on temporal-spectral residual network

High frequency (HF) communication is widely spread due to some merits like easy deployment and wide communication coverage. Spectrum prediction is a promising technique to facilitate the working frequency selection and enhance the function of automatic link establishment. Most of the existing spectrum prediction algorithms focus on predicting spectrum values in a slot-by-slot manner and therefore are lack of timeliness. Deep learning based spectrum prediction is developed in this paper by simultaneously predicting multi-slot ahead states of multiple spectrum points within a period of time. Specifically, we first employ supervised learning and construct samples depending on long-term and short-term HF spectrum data. Then, advanced residual units are introduced to build multiple residual network modules to respectively capture characteristics in these data with diverse time scales. Further, convolution neural network fuses the outputs of residual network modules above for temporal-spectral prediction, which is combined with residual network modules to construct the deep temporal-spectral residual network. Experiments have demonstrated that the approach proposed in this paper has a significant advantage over the benchmark schemes.

Link Quality Analysis Based Channel Selection in High-Frequency Asynchronous Automatic Link Establishment: A Matrix Completion Approach

Asynchronous automatic link establishment (ALE) has been utilized for decades in high-frequency communications due to its operational simplicity. During the process of ALE, the nodes select the channel with the best channel quality based on a link quality analysis (LQA) matrix, which is derived mainly from channel sounding. However, some elements in the matrix can be missing because of the failure of the channel sounding caused by interference or noise in the sounding phase. The incomplete LQA matrix may lead to bad channel selection. In this paper, by exploiting characteristics of low rank and periodicity in LQA matrix, a matrix completion approach is introduced to improve the channel selection in the asynchronous ALE with the goal of achieving maximum throughput in the data transmission. Simulation results show that, compared with the algorithm in current high-frequency ALE standard, the proposed approach of channel selection not only effectively selects the channel with the better channel quality, but also reduces the link establishment time, increasing the throughput of data transmission. In addition, the performance of the proposed algorithm approaches the channel selection algorithm with perfect LQA matrix.

On the Design of Automatic Link Establishment in High Frequency Networks

Most High Frequency (HF) communications systems deployed on the field today implement Automatic Link Establishment (ALE) techniques in order to help the HF stations automatically set up a link with good properties. Two generations (so called 2G and 3G ALE) have been standardized since the 90’s, and are today being revisited due to the emergence of wideband HF waveforms. In this paper, we develop Markovian models of the 2G ALE procedure, which is nowadays the most widely used as it can operate while being completely asynchronous. Our models are “channel oriented”, i.e., they observe the system from channel occupation perspective regardless of node status. We show by comparison with high-level OMNET++ simulations that our models provide fast and accurate estimation of all performance parameters of interest, and capture the main characteristics of the ALE process and the interactions between their numerous parameters. We believe that our work constitutes a useful tool to help operator plan and dimension HF networks. We also exploit the model to give some insight on the limitations of current 2G ALE, helping the design of future ALE strategies.

A New Simulation Architecture for Communication Network Systems with Application to HF Radio

 Abstract—This paper describes a simulation architecture developed to address the need in the defence and aerospace industry for a rapid prototyping capability to test new and existing network protocols and systems where analytical methods no longer suffice. In particular, the simulator introduced here allows study of High Frequency (HF) radio networks and other unorthodox systems that cannot be easily modelled using existing communications network simulators. This paper describes the architecture and gives an example use case - modelling an HF System using the 2G Automatic Link Establishment (ALE) linking protocol under a variety of conditions; exploring the effects of changing the number of nodes in the network, and of altering the input data rate to the system. The network performance was analysed under a wide range of combinations of conditions, and it was found that increasing the number of nodes in these networks causes specific latency increases and an overall throughput decrease, both in the unidirectional and bidirectional case, although it is better tolerated in the unidirectional case. Increasing the input data rate causes an overall throughput increase up to a threshold point, after which it saturates and then decreases as data remains unsent, due to the physical limits of the system (including networking overhead) being surpassed. This simulator, known as CommNetSim has been developed for use in evaluating the technical capabilities of, and business cases for, real-world applications to be developed by Thales UK. Index Terms—Communication networks, discrete event simulation, high frequency radio, modelling, simulation.

A novel fast link establishment method for mobile IP communication networks based on mobile Agent

A new method for establishing communication links fast in mobile IP networks for handoff based on mobile Agent was proposed.Combined with Multiple Protocol Label Switching(MPLS)and mobile Agent in the signal processing,an automatic dynamic fast link establishment was achieved,which could reduce the delay dramatically.Simulation shows that transmission delay can be reduced to 27 to 41 percent in switching.

High-accuracy angle detection for ultra-wide-field-of-view acquisition in wireless optical links

A novel scheme to deploy a point-to-multipoint optical wire- less communication network is proposed. The master node provides hemispherical field-of-view FOV acquisition via a fisheye lens to achieve the automatic establishment of optical links with user nodes. We present an effective distortion-correcting algorithm based on two-ary piecewise bicubic spline interpolation to correct the large optical distor- tions of the fisheye lens. Using this algorithm, the angles of the incident beams are accurately calculated according to the laser spot position on the CCD charge-coupled device sensor with the maximum error of 0.027 deg. In addition, the strong background radiation from such an ultrawide FOV also leads to significant degradation of the angle detec- tion accuracy under the condition of weak received optical power. A Voigt anomalous dispersion optical filter with ultra-narrow-pass bandwidth is adopted to resist the background radiation. The numerical simulation results show that the total angle detection error caused by the optical distortion and the background radiation is within 0.06 deg. Considering the extra gimbal pointing error and the angle-of-arrival fluctuations due to atmospheric turbulence, the pointing error of the master node is less than 0.079 deg, which meets the high-accuracy requirement of pointing for the automatic optical link establishment. © 2008 Society of Photo-Optical

Automatic and adaptive radio communication systems

Automatic and adaptive radio communication systems are developed to ensure better quality and easy link establishment and transmitting of messages over the HF radio channel. Automatic link establishment is a robust, adaptive HF radio method for automatic communications establishing over the HF SSB link. The overview of this technology, the principles of automatic link establishment and the analysis of conventional and adaptive radio systems are the contents of this paper. .