# A Survey of Blockchain Applications for Management in Agriculture and Livestock Internet of Things
## 2 Preliminaries
### Blockchain Technology in Agriculture and Animal Husbandry: An Overview  
Blockchain is an automated system programmed to activate and perform specific functions when predefined criteria are met. This functionality enables the automated and transparent execution of complex business processes on the blockchain, presenting immense potential value across various sectors. In this way, blockchain can automatically execute transaction information storage and operations under specific conditions, performing certain actions automatically (such as feeding or irrigation) when conditions like time, temperature, or humidity are met [51]. In supply chain tracking, blockchain can also store all transaction information through smart contracts [52]. Despite its strengths, blockchain technology confronts certain challenges. With the escalation in data volume on the blockchain, processing speed and storage demands increase, potentially affecting overall system efficiency [53]. Moreover, while blockchain is generally secure, it is not impervious to threats, including vulnerabilities like the 51% attack [54], contract vulnerabilities, and scalability issues. Additional concerns include interoperability, privacy exposure, and evolving regulatory landscapes, underscoring the need for ongoing advancements and solutions.  
Blockchain technology represents a distinctive database model that organizes data into linked blocks, creating a chain-like formation. Each block comprises a collection of transaction data, a timestamp, and cryptographic hashes of its preceding block, providing secure and unalterable records. In the blockchain, a series of blocks are linked together through encryption algorithms and are distributed and stored in a decentralized P2P network, ensuring the data's immutability and transparent sharing. With a consensus mechanism in place, potential data modifications can be agreed upon by the majority of network participants, thus maintaining a balance between immutability and adaptability. Additionally, the use of cryptographic technology secures data, and smart contracts automate contract conditions. Blockchain technology is categorized based on application scenarios and access permissions, showcasing its adaptability to various fields.  
Blockchain technology, based on different application scenarios and access permissions, is divided into the following categories:  
Public Blockchains [55]:  
Public blockchains are open blockchain networks that are accessible to everyone. Anyone can participate in the operation of the network, send and verify transactions, or participate in the creation of new blocks.  
Private Blockchains [56]:  
Private chains are controlled networks that only allow specific individuals or organizations to verify transactions and create blocks. These networks are typically used within enterprises, offering faster transaction speeds and better privacy protection.  
Consortium Blockchain [57]:  
As a variant of a private blockchain, consortium blockchain shows significant differences from traditional private chains. Private chains primarily serve the exclusive needs of a single company, whereas consortium blockchain focuses on collaboration between multiple companies or organizations, aiming to provide cross-industry services.  
Hybrid Blockchain [58]:  
Operating in a controlled environment akin to a private blockchain, the hybrid blockchain allows certain data and operations to be accessible by the public, aiming to merge the benefits of different blockchain types to offer solutions that ensure privacy protection while also providing transparency.