# A Practical and Efficient Node Blind SignCryption Scheme for the IoT Device Network
## 1 Introduction  
In recent years, Internet of Things(IoT for short) devices has widely applied in our daily life. From the life of human beings to industry 4.0, there are many common machines composed of several IoT devices such as the air conditioner, electronic vehicle, mobile phone, etc. These devices can collect physical signal data and transfer these data to a powerful gateway device of the IoT network through the Internet in a digital manner. When the gateway has received the sensed data from a sender node, it preserves these records in a database or cloud storage service. However, such IoT devices have limitations compared with a general gateway server, such as fewer memory space or limited computing power. This situation usually occurs in the communications between nodes of wireless sensing network(WSN for short) and IoT networks. Once an IoT device has collected physical data from a human body, it then must forward these data to the powerful gateway that can preserve the final result data into a database and perform other cryptography operations. From the above scenario, we discover that, if any IoT devices attempt to perform a heavy encryption/decryption computation such as modular exponentiation over a large prime number in a public key algorithm, then they must perform a signature operation later for concrete security protection and authentication on these sensed data. This will lead to fast power consumption and free-memory usage of these nodes. To solve the above situation, we adopt the sign-cryption approach to let a sensing node perform the lightweight sign-cryption operation and generate the final cipher-text with its own signature simultaneously on the powerful server side. When the gateway server has received this cipher-text from a sensor node, it can decrypt this cipher-text first, then perform the validation of this plain-text with the inside signature's help for data authentication. We consider the following situation of an IoT device called \(DS_{i}\) that attempts to transfer sensed data to a receiver called \(\mathcal{R}\), where \(i=1\sim l\) and \(l\) is the total number of all the sensor nodes. To keep the data confidential, \(DS_{i}\) must encrypt its own data first. At this time, it can adopt an efficient encryption/decryption method to generate a cipher-text. Then, \(DS_{i}\) can forward this cipher-text to a powerful base station (\(BS\) for short), which it equips with more computing power than all the sensor nodes in the same IoT network. However, \(DS_{i}\) must also consider its own memory limitation and remaining computing power to perform such encrypting/decryption computation in sequence. The node \(DS_{i}\) may not be able to perform the signature computation after it has generated encryption if the remaining power is not enough to perform signature generation in this time; thus, it must transfer the heavy computation to a powerful node such as the base station \(BS\). Due to the mentioned situations, we concluded that, if there exists an efficient method allowing IoT devices to perform encryption and signature operations on the sensed data in one operation, it could save more computing time and energy, which can then be used for other computations. In the recent literature, sign-cryption was discussed in [1; 2; 3; 4]. The authors claimed that the sender can transfer the data only to perform one sign-cryption time, and it can output a cipher-text with a guaranteed signature within. Then, the receiver can decrypt the received cipher-text with a secret random number inside the corresponding signature. When the signature is verified by the receiver successfully, the receiver can obtain the random secret value by applying its own secret key. Finally, the receiver \(\mathcal{R}\) can obtain the final data by inputting this secret random number to decrypt the cipher-text. Unfortunately, their computation efficiency are not practical to fit above situation for IoT device network. There are some research limitations in our proposed scheme.