# CoNTe: A Core Network Temporal Blockchain for 5G
## 2 Unbundling Blockchain for General Network Function Compatibility  
Early blockchain research has focused largely on individual use cases and, as a by-product, makes a toy example of the wider cellular network dependencies. However, this framing does not fully acknowledge the heterogeneity of wireless networks whose hardware is modified and upgraded over time; for example, the coordination of Mobile Network Operators (MNO) and subscribing Mobile Virtual Network Operators (MVNO), where blockchain can ensure the verifiability of data, but each carrier operates its own diverging, and possibly competing services. A given MVNO may even utilize infrastructures across multiple MNO's and, in this case, a level of compatibility, optionality, and generalizability of blockchain application would be desired. When the 3 GPP specification for 5G networks was released in 2018 [16], it explained its architecture as being comprised of many Network Service Functions (NSF) to support Network Function Virtualization (NFV) and Software Defined Networking (SDN) paradigms. It achieves this through modularity, separating hardware infrastructure into Control Plane (CP) and User Plane (UP) functions that are temporal, independently scalable, and loosely coupled to prevent structural dependencies when possible. Eighteen total service functions are identified within the \"Architecture Reference Model\" section of the 3 GPP specification, and they are listed below:* _Authentication Server Function (AUSF)_
* _Access and Mobility Management Function (AMF)_
* _Data Network (DN)_
* _Unstructured Data Storage Function (ULSF)_
* _Network Exposure Function (NEF)_
* _Network Repository Function (NRF)_
* _Network Slice Selection Function (NSSF)_
* _Policy Control Function (PCF)_
* _Session Management Function (SMF)_
* _Unified Data Management (ULDM)_
* _Unified Data Repository (ULDR)_
* _User Plane Function (UPF)_
* _Application Function (AF)_
* _User Equipment (UE)_
* _(Radio) Access Network ((R)AN)_
* _5G-Equipment Identity Register (5G-EIR)_
* _Security Edge Protection Proxy (SEPP)_
* _Network Data Analytics Function (NWDAF)_  
Today, there are two dominant paths of blockchain development. Either a bespoke chain can be created for the intended purpose, or a monolithic, single purpose chain may be deployed. Bitcoin contributed to the early work of [PERSON] and [PERSON] [18] in proving a system that could remain secure while being public [19]. As a digital currency, it was designed to be decentralized and permissionless; two traits not requisite in the original [PERSON] and Stornetta digital notary use. To achieve this however, Bitcoin deploys resource intensive Proof-of-Work (POW) consensus that imposes throughput constraint and is difficult to deploy to resource constrained network environments, such as IoT. This conflict is manifested in examples, such as [20; 21], which require the deployment of proxy devices that are able to run resource intensive POW calculations, or store the entirety of a public ledgers history, which is then referenced by appendage devices through an informal star topology. Taken in isolation, this full and light node separation can be understood as a symptom of the research relying on the POW variant of the Ethereum blockchain--but, in a macro perspective, represent a risk in network environments where the design and traits of a given blockchain evolve independently and potentially in conflict with wireless network design. An existing example evolution includes the introduction of Ethereum state channels, which impacts the auditability of data that would otherwise be stored in the main ledger [22]. Adopting a general use blockchain, such as Ethereum presents risk in that it lacks modularity of consensus, currency, contract, or other behaviors of operation. In Ethereum's case, this means adopting behaviors to support a POW permissionless security model backed by currency functions which may be superfluous or even detrimental to the intended cellular network use.