## 2 Background Knowledge  
In this section, we introduce the related technologies of blockchain and certificateless public key cryptography, which provide theoretical support for our proposed information acceleration strategy. 1. In essence, blockchain is a distributed database built by multiple independent nodes. Each node has independent storage and equal status. The data structure of blockchain can be described by the block, transaction and chain. The block is the basic storage unit in the blockchain, and records all the transaction information of each node within a certain time. Each block is linked by a random hash (also known as a hash algorithm), and then a chain is formed. Transactions in blocks are organized by a Merkle tree structure. Any change in the data in a block will cause a change in the total hash value of the transaction. This results in the disconnection of the blockchain from the block. Therefore, it can be ensured that the data are not easily tampered with, are difficult to forge, and are traceable [12]. The blockchain can be divided into the public blockchain, the private blockchain, and the consortium blockchain according to the degree of centralization. The public blockchain is a completely open chain that participants can fully access. The private blockchain consists of a single node that can record and maintain data in a ledger. The private blockchain is usually not open to external participants. The private blockchain platform is used for an organization or an enterprise; only authorized entities can join the system. The consortium blockchain is recorded and maintained by predetermined nodes. Whether a participant can access a consortium blockchain system is determined by the predetermined nodes. The consortium blockchain is an integration of semi-public and semi-private systems that has specific purposes for organizations and participants [13]. It retains other characteristics of blockchain and gradually becomes the mainstream in the field of commercial applications. Blockchain was a foundational element in the development of cryptocurrency; it was extended for use in various industrial scenarios to build trust and consensus within distributed systems. Blockchain-enabled systems and services have improved authentication, integrity, and immutability [14]. This means blockchain can promote the realization of secure, privacy preserving, and trusted smart grid developments [15]. 2. Certificateless public key cryptography (CL-PKC) refers to the technology of key distribution based on a public key cryptosystem without the help of certificate. It is a classic and widely used technical scheme in public key cryptography. CL-PKC is a typical representative certificateless cryptography, which is widely cited by current security workers. This scheme does not need a certificate managed key, and does not fully trust the key materials from the key generation center (KGC). In this scheme, the node judges whether the received key material is legal, and combines the legal part of the private key with the secret value held by itself to obtain the complete node private key. The following outlines the process of CL-PKC [16]:  
(1) System Initialization  
For initialization, KGC performs the following steps:  
KGC selects a master private key \(s\in Z_{P}^{*}\) and computes a master public key \(P_{pup}\in sP\), then chooses two hash functions in Formula (1). \[ \begin{array}{l}H_{1}:\{0,1\}\to G_{t}^{*}\\ H_{2}:G_{T}^{*}\rightarrow\{0,1\}^{l_{m}}\end{array}  \tag{1}\]  
Then, KGC publishes these parameters in Formula (2). \[\left\{G_{t},G_{T},l_{m},p,\hat{e},P,P_{pup},H_{1},H_{2}\right\} \tag{2}\]  
(2) Partial-Private-Key-GenerateKGC computes the partial private key of user \(D_{U}\) in Formula (3). \[D_{U}=sQ_{U}=sH_{1}(ID_{U}) \tag{3}\]  
(3) User-Key-Generate  
The user randomly selects a secret value \(x_{U}\in Z_{p}^{*}\), and the private key and public key are computed using Formula (4). \[