A system architecture, processor, and communication protocol for secure implants

Secure and energy-efficient communication between Implantable Medical Devices (IMDs) and authorized external users is attracting increasing attention these days. However, there currently exists no systematic approach to the problem, while solutions from neighboring fields, such as wireless sensor networks, are not directly transferable due to the peculiarities of the IMD domain. This work describes an original, efficient solution for secure IMD communication. A new implant system architecture is proposed, where security and main-implant functionality are made completely decoupled by running the tasks onto two separate cores. Wireless communication goes through a custom security ASIP, called SISC (Smart-Implant Security Core), which runs an energy-efficient security protocol. The security core is powered by RF-harvested energy until it performs external-reader authentication, providing an elegant defense mechanism agai

Comparison of Psychological Distress between Type 2 Diabetes Patients with and without Proteinuria

We investigated the link between proteinuria and psychological distress among patients with type 2 diabetes mellitus (T2DM). A total of 130 patients with T2DM aged 69.1±10.3 years were enrolled in this cross-sectional study. Urine and blood parameters, age, height, body weight, and medications were analyzed, and each patient’s psychological distress was measured using the six-item Kessler Psychological Distress Scale (K6). We compared the K6 scores between the patients with and without proteinuria. Forty-two patients (32.3%) had proteinuria (≥±) and the level of HbA1c was 7.5±1.3%. The K6 scores of the patients with proteinuria were significantly higher than those of the patients without proteinuria even after adjusting for age and sex. The clinical impact of proteinuria rather than age, sex and HbA1c was demonstrated by a multiple regression analysis. Proteinuria was closely associated with higher psychological distress. Preventing and improving proteinuria may reduce psychological distress in patients with T2DM

Cerebellar control of gait and interlimb coordination

Synaptic and intrinsic processing in Purkinje cells, interneurons and granule cells of the cerebellar cortex have been shown to underlie various relatively simple, single-joint, reflex types of motor learning, including eyeblink conditioning and adaptation of the vestibulo-ocular reflex. However, to what extent these processes contribute to more complex, multi-joint motor behaviors, such as locomotion performance and adaptation during obstacle crossing, is not well understood. Here, we investigated these functions using the Erasmus Ladder in cell-specific mouse mutant lines that suffer from impaired Purkinje cell output (Pcd), Purkinje cell potentiation (L7-Pp2b), molecular layer interneuron output (L7-Δγ2), and granule cell output (α6-Cacna1a). We found that locomotion performance was severely impaired with small steps and long step times in Pcd and L7-Pp2b mice, whereas it was mildly altered in L7-Δγ2 and not significantly affected in α6-Cacna1a mice. Locomotion adaptation triggered by pairing obstacle appearances with preceding tones at fixed time intervals was impaired in all four mouse lines, in that they all showed inaccurate and inconsistent adaptive walking patterns. Furthermore, all mutants exhibited altered front–hind and left–right interlimb coordination during both performance and adaptation, and inconsistent walking stepping patterns while crossing obstacles. Instead, motivation and avoidance behavior were not compromised in any of the mutants during the Erasmus Ladder task. Our findings indicate that cell type-specific abnormalities in cerebellar microcircuitry can translate into pronounced impairments in locomotion performance and adaptation as well as interlimb coordination, highlighting the general role of the cerebellar cortex in spatiotemporal control of complex multi-joint movements

Architecture-Level Fault-Tolerance Techniques for Biomedical Implants

In this thesis the design and implementation of a new fault-tolerant architecture is described. The design targets both soft and hard faults by implementing a combination of known fault-tolerance tech niques in an efficient way. The proposed architecture allows a trade-off to be made between performance and fault tolerance by means of instruction-level configurability. The design is evaluated in terms of fault coverage, area, average power consumption, total energy consumption and performance for various duplication policies and test-sequence schedules. It is shown that an area and power overhead of roughly 25% and 32%, respectively, are required to implement the techniques on the baseline processor. The main overheads of the architecture are performance (up to 106%) and energy consumption (up to 157%). It is observed that the average power consumption is often reduced when a higher degree of fault tolerance is set and therefore the energy consumption does not increase linearly with a higher execution time. It is shown that test sequences can effectively be scheduled during program stalls, and that nearly 100% of all soft faults are tolerated by using instruction duplication. The main advantages of using our techniques are the flexibility to make a trade-off between the overheads and the required degree of fault tolerance, the high portability of the used techniques and the small increase in area and power consumption.Computer EngineeringMicroelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc

Architecture-level fault-tolerance for biomedical implants

In this paper, we describe the design and implementation of a new fault-tolerant RISC-processor architecture suitable for a design framework targeting biomedical implants. The design targets both soft and hard faults and is original in efficiently combining as well as enhancing classic fault-tolerance techniques. The proposed architecture allows run-time tradeoffs between performance and fault tolerance by means of instruction-level configurability. The system design is synthesized for UMC 90nm CMOS standard-process and is evaluated in terms of fault coverage, area, average power consumption, total energy consumption and performance for various duplication policies and test-sequence schedules. It is shown that area and power overheads of approximately 25% and 32%, respectively, are required to implement our techniques on the baseline processor. The major overheads of the proposed architecture are performance (up to 107%) and energy consumption (up to 157%). It is observed that the average power consumption is often reduced when a higher degree of fault tolerance is targeted. It is shown that test sequences can effectively be scheduled during the available program stalls and that nearly all soft faults are tolerated by using instruction duplication. The main advantages of the proposed architecture are the high portability of the introduced architecture-level fault-tolerance techniques, the flexibility in trading processor overheads for required fault-tolerance degree as well as affordable area and power consumption overheads

On using a von neumann extractor in heart-beat-based security

The Inter-Pulse-Interval (IPI) of heart beats has previously been suggested for facilitating security in mobile health (mHealth) applications. In heart-beat-based security, a security key is derived from the time difference between consecutive heart beats. As two entities that simultaneously sample the same heart beats may generate the same key (with some inter-key disparity), these keys may be used for various security functions, such as entity authentication or data confidentiality. One of the key limitations in heart-beat-based security is the low randomness intrinsic to the most-significant bits (MSBs) in the digital representation of each IPI. In this paper, we explore the use of a von Neumann entropy extractor on these MSBs in order to increase their randomness. We show that our von Neumann key-generator produces significantly more random bits than a non-extracting key generator with an average bit-extraction rate between 13.4% and 21.9%. Despite this increase in randomness, we also find a substantial increase in inter-key disparity, increasing the mismatch tolerance required for a given true-key pair. Accordingly, the maximum-attainable effective key-strength of our key generator is only slightly higher than that of a non-extracting generator (16.4 bits compared to 15.2 bits of security for a 60-bit key), while the former requires an increase in average key-generation time of 2.5x

Adaptive entity-identifier generation for IMD emergency access

Recent work on wireless Implantable Medical Devices (IMDs) has revealed the need for secure communication in order to prevent data theft and implant abuse by malicious attackers. However, security should not be provided at the cost of patient safety and an IMD should, thus, remain accessible during an emergency regardless of device security. In this paper, we present a novel method of providing IMD emergency access, based on generating Entity Identifiers (EI) using the Inter-Pulse Intervals (IPIs) of heartbeats. We evaluate the current state-of-the-art in EI-generation in terms of security and accessibility for healthy subjects with a wide range of heart rates. Subsequently, we present an adaptive EI-generation algorithm which takes the heart rate into account, maintaining an acceptable emergency-mode activation time (between 5-55.4 s) while improving security by up to 3.4x for high heart rates. Finally, we show that activating emergency mode may consume as little as 0.24μJ from the IMD battery. Copyright \ua9 2014 ACM

Enhancing heart-beat-based security for mHealth applications

In heart-beat-based security, a security key is derived from the time difference between two consecutive heart beats (the Inter-Pulse-Interval, IPI) which may, subsequently, be used to enable secure communication. While heart-beatbased security holds promise in mobile health (mHealth) applications, there currently exists no work that provides a detailed characterization of the delivered security in a real system. In this paper, we evaluate the strength of IPI-based security keys in the context of entity authentication. We investigate several aspects which should be considered in practice, including subjects with reduced heart-rate variability, different sensor-sampling frequencies, inter-sensor variability (i.e., how accurate each entity may measure heart beats) as well as average and worst-caseauthentication time. Contrary to the current state of the art, our evaluation demonstrates that authentication using multiple, lessentropic keys may actually increase the key strength by reducing the effects of inter-sensor variability. Moreover, we find that the maximal key strength of a 60-bit key varies between 29.2 bits and only 5.7 bits, depending on the subject\u27s heart-rate variability. To improve security, we introduce the Inter-multi-Pulse Interval (ImPI), a novel method of extracting entropy from the heart by considering the time difference between two non-consecutive heart beats. Given the same authentication time, using the ImPI for key generation increases key strength by up to 3.4x (+19.2 bits) for subjects with limited heart-rate variability, at the cost of an extended key-generation time of 4.8x (+45 sec)

Secure key-exchange protocol for implants using heartbeats

The cardiac interpulse interval (IPI) has recently been pro-posed to facilitate key exchange for implantable medical de-vices (IMDs) using a patient\u27s own heartbeats as a source of trust. While this form of key exchange holds promise for IMD security, its feasibility is not fully understood due to the simplified approaches found in related works. For exam-ple, previously proposed protocols have been designed with-out considering the limited randomness available per IPI, or have overlooked aspects pertinent to a realistic system, such as imperfect heartbeat detection or the energy overheads im-posed on an IMD. In this paper, we propose a new IPI-based key-exchange protocol and evaluate its use during medical emergencies. Our protocol employs fuzzy commitment to tolerate the expected disparity between IPIs obtained by an external reader and an IMD, as well as a novel way of tack-ling heartbeat misdetection through IPI classification. Using our protocol, the expected time for securely exchanging an 80-bit key with high probability (1-106) is roughly one minute, while consuming only 88 ?J from an IMD

Peak misdetection in heart-beat-based security: Characterization and tolerance

The Inter-Pulse-Interval (IPI) of heart beats has previously been suggested for security in mobile health (mHealth) applications. In IPI-based security, secure communication is facilitated through a security key derived from the time difference between heart beats. However, there currently exists no work which considers the effect on security of imperfect heart-beat (peak) detection. This is a crucial aspect of IPI-based security and likely to happen in a real system. In this paper, we evaluate the effects of peak misdetection on the security performance of IPI-based security. It is shown that even with a high peak detection rate between 99.9% and 99.0%, a significant drop in security performance may be observed (between -70% and -303%) compared to having perfect peak detection. We show that authenticating using smaller keys yields both stronger keys as well as potentially faster authentication in case of imperfect heart beat detection. Finally, we present an algorithm which tolerates the effect of a single misdetected peak and increases the security performance by up to 155%