# Symmetric Encryption Relying on Chaotic Henon System for Secure Hardware-Friendly Wireless Communication of Implantable Medical Systems

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## Abstract

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## 1. Introduction

- Authentication: Authentication [2] is one of the most common ways to secure two communicating devices. It ensures that both ends communicate with an authentic and legitimate device, not an impersonator. Authentication in IMDs may be directed in two possible ways: through a direct authentication architecture or through an indirect authentication architecture. The indirect scheme introduces a proxy device used to perform authentication protocols, decreasing computation cost and communication overheads in the IMD devices. To identify the device that is requesting a communication, the IMD can use shared keys (temporary or permanent), auxiliary sensors like fingerprint scanners or other biometric signal collectors to identify the unit and to ascertain its authenticity.
- Cryptography: Cryptography [3,4] relies on shared secret keys to cipher the messages within a given communication. This prevents the understanding of the communication by external eavesdropping devices. Also, cryptography secures any system from any hijacking attempts. The adversary who intercepts a message is not able to perform any significant changes like the modification of the serial number in the aim of a spoofing attack. Nevertheless, standard encrypted communications are still vulnerable to Man-In-The-Middle (MITM) or replay attacks.
- Anomaly Detection: This technique [5] relies on the observation and the analysis of the received value by the device over time to conclude a pattern. Accordingly, the commands received by the device are estimated to be valid or invalid. For example, in the case of infusion pumps [6], the control device monitors and analyzes the infusion rate in the human body over seven to ten days to learn the time and a dosage pattern. This learning approach helps the device to recognize any malicious abnormal command for injection. Therefore, the patient is secured from receiving lethal injections through the IMD. Figure 1 shows an example of a normal injection rate of an infusion device. In the first sixteen hours, we can pinpoint an injection pattern over an eight-hour period. An adversary hijacks the device and prohibits the device from injection around 6 pm (line in red). The device can detect that this prohibition is quite different from what should be injected from the device (dotted blue line) and the anomaly detection algorithm will likely disregard this command.
- Jamming: Jamming attacks can be used to block any incoming packets to the IMD and block its regular work [7]. Moreover, this technique can be used to prevent other types of attacks on the device, mainly resource depletion and denial of service attacks. Attackers can blast the device with incoming messages, that can lead to a drastic drop in the battery level and overflows of memory and storage. In such scenarios, jamming techniques can be launched from the device itself or from an annexed Wearable External Device. If the device senses the existence of these messages, jamming techniques prevent the device from receiving and treating these packets.

- Analysis of the new symmetric key generation scheme for wireless cryptography based on PRNG derived from a low-dimensional chaotic system.
- Design of an efficient light-weight block cipher encryption scheme that uses fewer rounds than conventional encryption schemes with short-length keys.
- Investigation of the encryption scheme within an on-body to off-body communication channel.

## 2. Low-Dimensional Chaotic System

#### 2.1. Chaotic Systems

#### 2.2. Henon Scheme

## 3. Key Generation

**Y**will be the result of the XOR operation of the raw keys

**X**, and

**Y**generated from the equations as shown in Figure 5.

## 4. Cryptographic Unit System

#### 4.1. Diffusion and Confusion Blocks

**Confusion:**which is the property of drastically modifying data from the input to the output. In other words, each bit of the ciphertext should depend on several parts of the system.**Diffusion:**which is the property responsible for changing many different bits of the output when a single bit of the input is modified.

#### 4.2. Cryptographic Unit

#### 4.3. Featured Blocks

#### 4.3.1. Table LookUp

#### 4.3.2. Cipher Block

## 5. Communication Protocol

## 6. Statistical Tests

#### 6.1. Monobit Test

#### 6.2. Frequency Test within a Block

#### 6.3. Runs Test

#### 6.4. Test for the Longest Run of Ones in a Block

#### 6.5. Discrete Fourier Transform (Spectral) Test

## 7. Statistical Results of The Generated Keys

#### 7.1. NIST Test Results

#### 7.2. Pattern Existence

## 8. Key Performance Evaluation

#### 8.1. Sensitivity to the Initial State

#### 8.2. Diffusion of the Encryption System

#### 8.3. Key Change

#### 8.4. Body Area Communication Scenario

## 9. Hardware Implementation

## 10. Conclusions

## Author Contributions

## Acknowledgments

## Conflicts of Interest

## References

- Denning, D.E. Information Warfare and Security; Addison-Wesley: Boston, MA, USA, December 1998. [Google Scholar]
- Wu, L.; Du, X.; Guizani, M.; Mohamed, A. Access Control Schemes for Implantable Medical Devices: A Survey. IEEE Internet Things J.
**2017**, 4, 1272–1283. [Google Scholar] [CrossRef] - Kumar, P.; Lee, H.J. Security Issues in Healthcare Applications Using Wireless Medical Sensor Networks: A Survey. Sensors
**2012**, 12, 55–91. [Google Scholar] [CrossRef] [PubMed] - Du, X.; Guizani, M.; Xiao, Y.; Chen, H.H. A Routing-Driven Elliptic Curve Cryptography based Key Management Scheme for Heterogeneous Sensor Networks. IEEE Trans. Wirel. Commun.
**2009**, 8, 1223–1229. [Google Scholar] [CrossRef] - Zhang, M.; Raghunathan, A.; Jha, N.K. MedMon: Securing Medical Devices Through Wireless Monitoring and Anomaly Detection. IEEE Trans. Biomed. Circuits Syst.
**2013**, 7, 871–881. [Google Scholar] [CrossRef] [PubMed] - Rathore, H.; Mohamed, A.; Al-Ali, A.; Du, X.; Guizani, M. A Review of Security Challenges, Attacks and Resolutions for Wireless Medical Devices. In Proceedings of the 2017 13th International Wireless Communications and Mobile Computing Conference (IWCMC), Valencia, Spain, 26–30 June 2017. [Google Scholar]
- Law, Y.W.; Palaniswami, M.; van Hoesel, L.; Doumen, J.; Hartel, P.; Havinga, P. Energy-Efficient Link-Layer Jamming Attacks against Wireless Sensor Network MAC Protocols. ACM Trans. Sens. Netw.
**2009**, 5. [Google Scholar] [CrossRef] - Vaudenay, S. A Classical Introduction to Cryptography; Springer: New York, NY, USA, 2005. [Google Scholar]
- Halperin, D.; Heydt-Benjamin, T.S.; Ransford, B.; Clark, S.S.; Defend, B.; Morgan, W.; Fu, K.; Kohno, T.; Maisel, W.H. Pacemakers and implantable cardiac defibrillators: Software radio attacks and zero-power defenses. In Proceedings of the IEEE Symposium on Security and Privacy, 2008 (SP 2008), Oakland, CA, USA, 18–22 May 2008. [Google Scholar]
- Pecora, L.M.; Carroll, T.L. Driving systems with chaotic signals. Phys. Rev. A
**1991**, 44. [Google Scholar] [CrossRef] - Nien, H.H.; Huang, C.K.; Changchien, S.K.; Shieh, H.W.; Chen, C.T.; Tuan, Y.Y. Digital color image encoding and decoding using a novel chaotic random generator. Chaos Solitons Fractals
**2007**, 32, 1070–1080. [Google Scholar] [CrossRef] - Bing, Q.; Liang-rui, T.; Jing, L.; Yi, S. A new chaotic secure communication system. In Proceedings of the 2nd International Conference on Wireless, Mobile and Multimedia Networks, Beijing, China, 12–15 October 2008. [Google Scholar]
- Gonzales, O.A.; Han, G.; de Gyvez, J.P.; Sanchez-Sinencio, E. Lorenz-based chaotic cryptosystem: A monolithic implementation. IEEE Trans. Circuits Syst. I Fundam. Theory Appl.
**2000**, 47, 1243–1247. [Google Scholar] [CrossRef] - Wang, X.Y.; Yang, L.; Liu, R.; Kadir, A. A chaotic image encryption algorithm based on perceptron model. Nonlinear Dyn.
**2010**, 62, 615–621. [Google Scholar] [CrossRef] - Guan, Z.H.; Huang, F.; Guan, W. Chaos-based image encryption algorithm. Phys. Lett. A
**2005**, 346, 153–157. [Google Scholar] [CrossRef] - Liu, H.; Wang, X. Color image encryption using spatial bit-level permutation and high-dimension chaotic system. Opt. Commun.
**2011**, 248, 3895–3903. [Google Scholar] [CrossRef] - Wei, X.; Guoa, L.; Zhanga, Q.; Zhanga, J.; Lian, S. A novel color image encryption algorithm based on DNA sequence operation and hyper-chaotic system. J. Syst. Softw.
**2012**, 85, 290–299. [Google Scholar] [CrossRef] - Belkhouja, T.; Mohamed, A.; Al-Ali, A.K.; Du, X.; Guizani, M. Light-weight encryption of wireless communication for implantable medical devices using henon chaotic system (invited paper). In Proceedings of the International Conference on Wireless Networks and Mobile Communications (WINCOM), Rabat, Morocco, 1–4 November 2017. [Google Scholar]
- Short, K.M. Unmasking a modulated chaotic communications scheme. Int. J. Bifurcat Chaos
**1995**, 6. [Google Scholar] [CrossRef] - Li, H.J.; Chern, J.L. Coding the chaos in a semiconductor diode for information transmission. Phys. Lett. A
**1995**, 206, 217–221. [Google Scholar] [CrossRef] - Yu, Y.H.; Kwak, K.; Lim, T.K. Secure communication using small time continuous feedback. Phys. Lett. A
**1995**, 197, 311–315. [Google Scholar] [CrossRef] - Menezes, A.J.; van Oorschot, P.C.; Vanstone, S.A. Handbook of Applied Cryptography; CRC Press: Boca Raton, FL, USA, 2001. [Google Scholar]
- Henon, M. A Two-Dimensional Mapping with a Strange Attractor. Commun. Math. Phys.
**1976**, 50, 69–77. [Google Scholar] [CrossRef] - Richter, H. The generalized Henon maps: Examples for higher-dimensional chaos. Int. J. Bifurcation Chaos
**2002**, 12. [Google Scholar] [CrossRef] - Al-Shameri, W.F.H. Dynamical Properties of the Hénon Mapping. Int. J. Math. Anal.
**2012**, 6, 2419–2430. [Google Scholar] - Xiao, L.; Greenstein, L.; Mandayam, N.; Trappe, W. Fingerprints in the Ether: Using the Physical Layer for Wireless Authentication. In Proceedings of the IEEE International Conference on Communications, Glasgow, UK, 24–28 June 2007. [Google Scholar]
- Xiao, Y.; Chen, H.H.; Du, X.; Guizani, M. Stream-based Cipher Feedback Mode in Wireless Error Channel. IEEE Trans. Wirel. Commun.
**2009**, 8, 622–626. [Google Scholar] [CrossRef] - Du, X.; Xiao, Y.; Guizani, M.; Chen, H.H. An Effective Key Management Scheme for Heterogeneous Sensor Networks. Ad Hoc Netw.
**2007**, 5, 24–34. [Google Scholar] [CrossRef] - Cheng, Y.; Fu, X.; Du, X.; Luo, B.; Guizani, M. A lightweight live memory forensic approach based on hardware virtualization. Inf. Sci.
**2017**, 379, 23–41. [Google Scholar] [CrossRef] - Beierle, C.; Jovanovic, P.; Lauridsen, M.M.; Leander, G.; Rechberger, C. Analyzing Permutations for AES-like Ciphers: Understanding Shift Rows. In Proceedings of the Conference: Topics in Cryptology (CT-RSA), San Francisco, CA, USA, 20–24 April 2015. [Google Scholar]
- Van Tilborg, H.C.A.; Jajodia, S. Encyclopedia of Cryptography and Security; Springer: New York, NY, USA, 2005. [Google Scholar]
- Li, C.; Raghunathan, A.; Jha, N.K. Hijacking an Insulin Pump: Security Attacks and Defenses for a Diabetes Therapy System. In Proceedings of the IEEE 13th International Conference on e-Health Networking, Applications and Services, Columbia, MO, USA, 13–15 June 2011. [Google Scholar]
- Shannon, C. Communication Theory of Secrecy Systems. Bell Syst. Tech. J.
**1949**, 28, 656–715. [Google Scholar] [CrossRef] - National Institute of Standards and Technology. The Keved-Hash Message Authentication Code; Federal Information Processing Standards Publication; NIST: Gaithersburg, MD, USA, 2001.
- Ray, J.; Koopman, P. Efficient High Hamming Distance CRCs for Embedded Networks. In Proceedings of the International Conference on Dependable Systems and Networks, Philadelphia, PA, USA, 25–28 June 2006. [Google Scholar]
- National Institute of Standards and Technology. A Statistical Test Suite for Random and Pseudorandom Number Generators for Cryptographic Applications; National Institute of Standards and Technology: Gaithersburg, MD, USA, 2010.
- Vergili, I.; Yücel, M. Avalanche and Bit Independence Properties for the Ensembles of Randomly Chosen nxn S-Boxes. Turk. J. Electr. Eng.
**2001**, 9, 137–145. [Google Scholar] - Otto, C.; Milenkovic, A.; Sanders, C.; Jovanov, E. System Architecture of a Wireless Body Area Sensor Network for Ubiquitous Health Monitoring. J. Mob. Multimed.
**2006**, 1, 307–326. [Google Scholar] - Demir, A.F.; Ankaralı, Z.E.; Abbasi, Q.H.; Liu, Y.; Qaraqe, K.; Serpedin, E.; Arslan, H.; Gitlin, R.D. In Vivo Communications: Steps Toward the Next Generation of Implantable Devices. IEEE Veh. Technol. Mag.
**2016**, 11, 32–42. [Google Scholar] [CrossRef] - Yazdandoost, K.Y.; Sayrafian-Pour, K. IEEE P802.15-08-0780-09-0006 Channel Model for Body Area Network (BAN); IEEE: New York, NY, USA, 2009. [Google Scholar]
- Cotton, S.L.; Scanlon, W.G. A Statistical Analysis of Indoor Multipath Fading for a Narrowband Wireless Body Area Network. In Proceedings of the IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, Helsinki, Finland, 11–14 September 2006. [Google Scholar]
- Wang, J.; Wang, Q. Body Area Communications: Channel Modeling, Communication Systems, and EMC; IEEE Press: New Yor, NY, USA, 2013. [Google Scholar]
- Marin, E.; Singele, D.; Yang, B.; Verbauwhede, I.; Preneel, B. On the Feasibility of Cryptography for a Wireless Insulin Pump System. In Proceedings of the Sixth ACM Conference on Data and Application Security and Privacy, New Orleans, LA, USA, 9–11 March 2016. [Google Scholar]
- Xilinx. Spartan-6 Family Overview; Xilinx: San Jose, CA, USA, 2011. [Google Scholar]
- Xilinx. ISim User Guide; Xilinx: San Jose, CA, USA, April 2012. [Google Scholar]

**Figure 11.**Sensitivity of Key Bits towards the Initial Conditions Variation. (

**a**) Initial value difference in order of ${10}^{-2}$; (

**b**) Initial value difference in order of ${10}^{-6}$.

**Figure 15.**Bit Change Rate of the Packet When Only Flag Changes. (

**a**) Eavesdropping 10 Different Messages; (

**b**) Eavesdropping 50 Different Messages; (

**c**) Eavesdropping 100 Different Messages.

**Figure 17.**BER performace for in-body to off-body UWB static shadow fading (${\sigma}_{dB}=10\phantom{\rule{3.33333pt}{0ex}}\mathrm{dB}$) communication channel.

${\mathit{c}}_{\mathit{i}}$ | $\mathit{M}=8$ | $\mathit{M}=16$ |
---|---|---|

${c}_{0}$ | $k\le 1$ | $k\le 4$ |

${c}_{1}$ | $k=2$ | $k=5$ |

${c}_{2}$ | $k=3$ | $k=6$ |

${c}_{3}$ | $k\ge 4$ | $k=7$ |

${c}_{4}$ | — | $k=8$ |

${c}_{5}$ | — | $k\ge 9$ |

M | L | N |
---|---|---|

8 | 3 | 16 |

128 | 5 | 49 |

Test Name | X Key | Y Key |
---|---|---|

Monobit Test | Pass | Pass |

Frequency within a block | Pass | Pass |

Run Test | Pass | Pass |

Longest Run | Pass | Pass |

DFT (Spectral) | Pass | Pass |

Parameter | Value |
---|---|

${P}_{t}$ | −2.55 dBm |

${T}_{a}$ | 310 K |

${T}_{0}$ | 300 K |

${N}_{F}$ | 6 dB |

${f}_{b}$ | 10 Mbps |

Device | Summary | Design | |
---|---|---|---|

Number of occupied Slices | 18 | out of | 1430 |

Number of Slice Register | 51 | out of | 54,576 |

Number of Slice LUTs | 464 | out of | 27,288 |

IO Utilization | 68 |

Device | Summary | Design | |
---|---|---|---|

Number of occupied Slices | 18 | out of | 1430 |

Number of Slice Register | 40 | out of | 11,440 |

Number of Slice LUTs | 60 | out of | 5720 |

Number of fully used LUT-Flip Flop pairs | 39 | out of | 61 |

Device | Summary | Design | |
---|---|---|---|

Number of occupied Slices | 300 | out of | 1430 |

Number of Slice Register | 840 | out of | 11,440 |

Number of Slice LUTs | 514 | out of | 5720 |

Number of fully used LUT-Flip Flop pairs | 98 | out of | 61 |

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**MDPI and ACS Style**

Belkhouja, T.; Du, X.; Mohamed, A.; Al-Ali, A.K.; Guizani, M.
Symmetric Encryption Relying on Chaotic Henon System for Secure Hardware-Friendly Wireless Communication of Implantable Medical Systems. *J. Sens. Actuator Netw.* **2018**, *7*, 21.
https://doi.org/10.3390/jsan7020021

**AMA Style**

Belkhouja T, Du X, Mohamed A, Al-Ali AK, Guizani M.
Symmetric Encryption Relying on Chaotic Henon System for Secure Hardware-Friendly Wireless Communication of Implantable Medical Systems. *Journal of Sensor and Actuator Networks*. 2018; 7(2):21.
https://doi.org/10.3390/jsan7020021

**Chicago/Turabian Style**

Belkhouja, Taha, Xiaojiang Du, Amr Mohamed, Abdulla K. Al-Ali, and Mohsen Guizani.
2018. "Symmetric Encryption Relying on Chaotic Henon System for Secure Hardware-Friendly Wireless Communication of Implantable Medical Systems" *Journal of Sensor and Actuator Networks* 7, no. 2: 21.
https://doi.org/10.3390/jsan7020021