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Ensuring security and respect for users' privacy, especially in electronic health-care systems, is an important task that is achievable by authentication protocols. The security of many protocols is based on public-key cryptography, the breaking of which depends on solving a hard problem, e.g. Quadratic Residue (QR) which is compatible with constrained devices and is based on integer factoring with the Mean time complexity of e x p c + o (1) log 1 / 3 (n) log 2 / 3 log (n) for some c < 2 . In this paper, we introduce a vulnerability in QR-based problems for reducing the time complexity from Mean case to Min one and present an algorithm with time complexity O (log 2 (n)) to calculate user's session keys and finding confidential user's data by passive monitoring of the transmitted data over public networks for 2048-bit public keys in 6.9 μ s . To prove the efficiency of the proposed attacks, we address 12 vulnerable QR-based authentication protocols and show that the structure of all vulnerable transmitted messages is limited to 6 cases while messages in n , n - n are safe from the proposed method. Also, two recent authentication protocols have been analyzed in detail to show the consequences of the proposed vulnerability. [ABSTRACT FROM AUTHOR]

The Internet of Things (IoT), as one of the hottest topics, supports resource-constrained devices which can communicate with each other at any time. Moreover, the communication must be secure on public networks, and it is sometimes necessary to control remote devices using a secure protocol. Consequently, designing a lightweight protocol is one of the challenging points to be addressed. So far, several lightweight protocols have been proposed―this paper analyzes one of the current lightweight authentication protocols for the IoT. Based on the previous protocol, a secure protocol has been suggested that inherits the benefits of the previous one, while it is completely safe against the proposed attacks. The proposed protocol fulfils mutual authentication using BAN logic, as a broadly accepted formal method in security analysis. Moreover, the proposed protocol resists well-known attacks and its security, communication overhead, and time complexity have been compared with similar protocols that show its efficiency for IoT applications. In the proposed protocol, users and IoT nodes share a secret key in 3.122 ms with 528 bytes communication overhead. [ABSTRACT FROM AUTHOR]

Smart city is an important concept in urban development. The use of information and communication technology to promote quality of life and the management of natural resources is one of the main goals in smart cities. On the other hand, at any time, thousands of mobile users send a variety of information on the network, and this is the main challenge in smart cities. To overcome this challenge and collect data from roaming users, the global mobility network (GLOMONET) is a good approach for information transfer. Consequently, designing a secure protocol for GLOMONET is essential. The main intention of this paper is to provide a secure protocol for GLOMONET in smart cities. To do this, we design a protocol that is based on Li et al.'s protocol, which is not safe against our proposed attacks. Our protocol inherits all the benefits of the previous one; it is entirely secure and does not impose any more communication overhead. We formally analyze the protocol using BAN logic and compare it to similar ones in terms of performance and security, which shows the efficiency of our protocol. Our proposed protocol enables mobile users and foreign agents to share a secret key in 6.1 ms with 428 bytes communication overhead, which improves the time complexity of the previous protocol to 53%. [ABSTRACT FROM AUTHOR]