## 4 Devices' Vulnerabilities and Requirements
### Classification of IoT Security Attacks on Different Layers of IoT Networks
#### 4.6.2 Encryption Attack  
Encryption attack is of making vulnerable to the encryption scheme which is being used in the IoT system. * Man in the Middle Attack: The man-in-the-middle attack is a cyberattack where the attacker takes a position between two users on the communication line and shares keys with both users. The adversary can intercept the signal that both users are sending to each other and can encrypt or decrypt data with the keys that he shares with both of them. An attacker can also alter the communications between two parties without their knowledge who think that they are sending data to each other [120]. * Side-Channel Attacks: Physical characteristics of IoT devices (e.g., power consumption, execution time, electromagnetic leaks, system fault, etc.) can reveal sensitive information. During the execution time of IoT devices, the intruder performs different tests to extract confidential information. Sometimes it is required to have technical knowledge of the inner working principle of the system, which will be exploited. In public-crypto systems such as RSA, extracting information from the device's behavior is common [23]. RSA performs encryption and decryption of messages using private and public keys based on modular operations and large exponential values. The simple multiplication method is applied to modular operations, whereas the modular operations method is used on large exponential values. The attacker performs delay analysis to get how much time is required for calculating exponential results. \begin{table}
\begin{tabular}{p{56.9 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Physical Attacks** & **Compromised Security Requirements** & **Effects** & **Countermeasures** \\ \hline Malicious Code Injection & ALL & Loss of software integrity, Access to sensitive information and Gain access, DoS & Chain of trust, API endpoint security [102], Traffic monitoring and detection scheme [109], Tamper protection and self-destruction, IDS \\ \hline RF Interference & ALL & Message block [91], DoS & Distance-based information, Secure kill command for tags, Electronic Product Code (EPC) tags [63], spread-spectrum communication [110], Anti-jamming beamforming scheme [91] \\ \hline Tag Cloning & ALL & Unauthorized copy of tag & Attack probability scheme [111], Tag randomization [112], Encryption, hash-based methods, authentication framework, kill sleep instruction, isolation, blocking, distance estimation, Integrating PUFs into RFID tags \\ \hline Eavesdropping & C, NR, P & Extract critical network information [102] & Secure Bootstrapping [63], low-cost demilitarized zone [102], Encryption techniques, shift data to the back end \\ \hline Tag Tampering & ALL & Malicious altercation of data in tag memory [113] & Authentication watermark and recovery Watermark [114], Integration of PUFs into RFID tags, hash-based mechanisms, encryption, tamper-release layer RFID, integrating alarm option for active Tags \\ \hline Outage attack & A, AC, P, AU, NP & Disrupt or bias the state of applications [115] & Random time hopping sequence and random permutation [115], Secure physical design \\ \hline Object replication & ALL & Control network [116] & 3-D backward key chains based on deployment knowledge [117], Encryption, Hash-based methods, lightweight cartographic schemes \\ \hline Hardware Trojan & ALL & Function change of chips and sensitive information leakage [118] & Temporal thermal information [118], Electromagnetic radiation [119], Side-channel signal assessment (based on path-delay fingerprint, based on symmetry breaking, based on thermal and power, machine learning application), trojan activation \\ \hline \hline \end{tabular}
\end{table} 
Table 6: _Cont._Attackers can obtain private information like private keys by learning the computation time and using knowledge of the implementation technique. Most IoT devices will implement security measures like encryption to protect their sensitive information for security reasons. However, by performing a side-channel attack security mechanism can be broken.