Users often take blockchain protocols for granted when analyzing the potential of a cryptocurrency. The different blockchain protocols used can play a prominent role in the success of a cryptocurrency .
From Wikipedia - 1: A blockchain is a growing list of records, called blocks, which are linked using cryptography. Each block contains a cryptographic hash of the previous block, a time stamp, and transaction data (generally represented as a Merkle tree root hash) .
From Wikipedia - 2: A security protocol (cryptographic protocol or encryption protocol) is an abstract or concrete protocol that performs a security-related function and applies cryptographic methods, often as sequences of cryptographic primitives. A protocol describes how the algorithms should be used. A sufficiently detailed protocol includes details about data structures and representations, at which point it can be used to implement multiple, interoperable versions of a program .
From Market Protocol: A protocol can be seen as a methodology agreed upon by two or more parties that establish a common set of rules that
they can agree upon so as to enter into a binding agreement. Protocols are therefore the set of rules that govern the network. Blockchain protocols usually include rules about consensus, transaction validation and network participation .
From Encyclopaedia Britannica: Protocol, in computer science, is a set of rules or procedures for transmitting data between electronic devices, such as computers. In order for computers to exchange information, there must be a preexisting agreement as to how the information will be structured and how each side will send and receive it. Without a protocol, a transmitting computer, for example, could be sending its data in eight-bit packets while the receiving computer might expect the data in 16-bit packets .
 "A List of Blockchain Protocols - Explained and Compared" [online]. Available: https://cryptomaniaks.com/blockchain-protocols-list-explained. Date accessed: 2019‑06‑11.
 Wikipedia: "Cryptographic Protocol" [online]. Available: https://en.wikipedia.org/wiki/Cryptographic_protocol. Date accessed: 2019‑06‑11.
 "Protocol - Computer Science" [online]. Encyclopaedia Britannica. Available: https://www.britannica.com/technology/protocol-computer-science. Date accessed: 2019‑06‑11.