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Overview of the NIST Blockchain Prototypes Stephen Nightingale, NIST Information Technology Laboratory May 2017

Bitcoin is the first and the iconic instance of a Blockchain application for a cryptocurrency. It has the original (nakamoto) implementation in C++, and a later implementation in GOlang, available on GitHub (https://github.com/btcsuite/btcd). In full, it is a cryptocurrency with decentralized control of the ledger, and universal access. Anyone can participate as a wallet user,, getting and spending Bitcoins, or by deploying a node, tracking and mining Bitcoins and contributing to the ledger maintenance.

Bitcoin introduced a new data structure, the blockchain, as a secure public means of storing and transferring currency, and other information. It employs cryptographic concepts and tools such as public/private key pairs, and hashes (and hashes of hashes). Since the implementation employs complex layers of dereferencing, it is difficult code to read, understand and modify. The object of this project, then, is to develop cryptocurrency models from the simplest, to the progressively more complex, while introducing concepts using in the development of Bitcoin.

We hope that this will offer the curious a path to understanding Bitcoin, and code to use to develop alternative concepts. It is offered as a tool for modelling Blockchain development and exploration.

All the early models in this repository are centralized. A summary of the existing models is:

Model 0: introduces immutable coins, identified by transaction ID, with ownership identified by hash. The ledger is a linear list. The outputs are signed by the sender to indicate transfer of ownership. README0.txt inside this folder explains how the original model works.

Model 1: introduces transactions that aggregate value in one, or few, coins, where the sender pays the receiver and gives 'change' back to himself. README1.txt inside this folder explains how the first upgrade works.

Model 2: extends the ledger to include blocks which are backchained by hash pointers, with each block containing a Merkle Tree having 2**N transactions. README2.txt inside this folder explains how the second upgrade works.

Forthcoming models not yet installed here:

Model 3: introduces payment by Scripts, where the new owner of a coin value stipulates the procedure by which it can be redeemed.

The project is developed using Golang version 1.6. Once you have that installed, with your $GOPATH set, everything can be compiled using: $ python gobuilder.py

Individual Golang module functions are illuminated by:

$ python helpers.py unblock.go (or genesis.go, or ...)