## 3 Blockchain and Tracking Technologies in the Raw Material Sector
### Minespider's Blockchain  
To illustrate a blockchain that has been designed for supply chain transparency and collaboration along complex supply chains, Minespider's blockchain shall be outlined in more detail:  
Minespider developed a public, permissioned blockchain using GETH [24] nodes and a proof-of-authority consensus mechanism that connects supply chain data and documents by encrypting them in linked, digital certificates (also referred to as \"product passports\"). An essential feature of Minespider's type of public-permissioned blockchain is that everyone can have access to the public blockchain, but only nodes that have been accredited to the consortium are authorized to seal blocks. If a new sealer requests to be accredited, a vote takes place and with 50%+ of the votes the new account gets accredited.  
Minespider has frontend applications and templates for manual use, as well as APIs for process automations. Minespider is data agnostic in the sense that input data of any format can be included in a product passport and secured in an immutable way on blockchain and to be shared along a supply chain. This can, for example, include pdfs, images, videos and other formats of documentation. It can also include input of any format generated by physical trackers. Product passports include an individual QR code that can be scanned by standard scanning tools (e.g., via a smartphone) to provide access to the public data associated with the passport and to request permission to access secured data. These QR codes can be printed and affixed to shipments, or laser printed directly onto the materials themselves. Moreover, product passports provide a proof of provenance and a chain of custody along a supply chain. This way the Minespider infrastructure can help to bridge gaps resulting from the combination of different sources, or stages of production, and also to enable a circular economy.  
To balance the requirements of transparency and confidentiality along a supply chain, Minespider provides tools to easily manage different layers of confidentiality and transparency according to the respective needs of participants along complex supply chains. Information that is assigned to the public layer is visible to anyone. Information a user assigned to the private layer is visible to the immediate contractual partners only, whereas the transparent layer is visible along the respective supply chain(s).  
To support the different layers of transparency, Minespider works with nested hashes. This means that separate hashes are generated from encrypted data and in accordance with the respective layer the data has been assigned to by the person who uploaded and filed that data. The hash codes of data that are stored in the respective transparency or private layer, are hashed again and stored in the public layer, which again is stored on the blockchain. This way, Minespider can provide that everyone can see, compare, and validate data on the public layer. But to be able to decrypt and see the data that was assigned to the private or transparency layer requires the respective authorization(s) and key(s) to decrypt and read this data. Minespider's blockchain provides for greater legal compliance and a high level of throughput and scalability at low latency.