Blockchain with JWT

example.md

Example Ledger

When decoded, each block refers to the previous block in the chain.

1. eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJ2MS4wLjAiLCJpYXQiOjE1Nzk1MTU2MTcsInNpZyI6IiIsImRhdCI6e319.rqmyHA3pgvwSLPS7Arj2pz3KS5rK14ZJNHv3BCAB2b4

{
  "iss": "v1.0.0",
  "iat": 1579515617,
  "sig": "",
  "dat": {}
}

2. eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJ2MS4wLjAiLCJpYXQiOjE1Nzk1MTY5MzksInNpZyI6InJxbXlIQTNwZ3Z3U0xQUzdBcmoycHozS1M1cksxNFpKTkh2M0JDQUIyYjQiLCJkYXQiOnsibWVzc2FnZSI6IlRoaXMgaXMgdGhlIGZpcnN0IGdlbmVyYXRlZCBibG9jayEifX0.ZE-S8vKJqU-PKJdNaXpBhl3632GQOpxZJFGziY1LSc4

{
  "iss": "v1.0.0",
  "iat": 1579516939,
  "sig": "rqmyHA3pgvwSLPS7Arj2pz3KS5rK14ZJNHv3BCAB2b4",
  "dat": {
    "message": "This is the first generated block!"
  }
}

3. eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJ2MS4wLjAiLCJpYXQiOjE1Nzk1MTcwMDAsInNpZyI6IlpFLVM4dktKcVUtUEtKZE5hWHBCaGwzNjMyR1FPcHhaSkZHemlZMUxTYzQiLCJkYXQiOnsibWVzc2FnZSI6IkFuZCB3ZSBjYW4gc3RvcmUgYW55IEpTT04gZGF0YS4ifX0.wSkBOIdUzZgVom4_Dz8RmE8buiJnd4up5PksIT72IRA

{
  "iss": "v1.0.0",
  "iat": 1579517000,
  "sig": "ZE-S8vKJqU-PKJdNaXpBhl3632GQOpxZJFGziY1LSc4",
  "dat": {
    "message": "And we can store any JSON data."
  }
}

4. eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJ2MS4wLjAiLCJpYXQiOjE1Nzk1MTcwMTksInNpZyI6IndTa0JPSWRVelpnVm9tNF9EejhSbUU4YnVpSm5kNHVwNVBrc0lUNzJJUkEiLCJkYXQiOnsibWVzc2FnZSI6IllvdSBzaG91bGQgcGFyc2UgYGRhdGAgYmFzZWQgb24gdGhlIHVuaXF1ZSBgaXNzYC4gQW55dGhpbmcgaXMgcG9zc2libGUhIn19.F6222nCVGy5JieDlDK_ROwZWrJov1VjvjRhs5YXFS-4

{
  "iss": "v1.0.0",
  "iat": 1579517019,
  "sig": "wSkBOIdUzZgVom4_Dz8RmE8buiJnd4up5PksIT72IRA",
  "dat": {
    "message": "You should parse `dat` based on the unique `iss`. Anything is possible!"
  }
}

implementation.ts

// Extremely simple blockchain service

// Needs implementation of JWT service, so it automatically calculates next JWT in chain

interface Token {
  iss: string
  iat: number
  sig: string
  dat: any
}

interface Blockchain {
  add: (data: string) => void
  getStore: () => string[]
  getLastBlockSignature: () => string
  getBlockData: (index: number) => Token
}

function JWTBlockchain (genesis: string): Blockchain {
  const _store: [string] = [genesis]

  function _validate (candidate: string): boolean {
    try {
      const lastBlock: string = _store[_store.length - 1]
      const parsedLastBlock: Token = JSON.parse(atob(lastBlock.split('.')[1]))
      const lastBlockSignature: string = getLastBlockSignature()
      const parsedCandidate: Token = JSON.parse(atob(candidate.split('.')[1]))
      
      const versionMatches: boolean = parsedCandidate.iss === parsedLastBlock.iss
      const signatureMatches: boolean = parsedCandidate.sig === lastBlockSignature
      const issuedLater: boolean = parsedCandidate.iat > parsedLastBlock.iat
      if (versionMatches && signatureMatches && issuedLater) {
        return true
      } else {
        return false
      }
    } catch (err) {
      return false
    }
  }

  function add (data: string): void {
    if (_validate(data)) {
      _store.push(data)
    }
  }

  function getStore (): string[] {
    return _store.slice()
  }

  function getLastBlockSignature (): string {
    return _store[_store.length - 1].split('.')[2]
  }

  function getBlockData (index: number): Token {
    if (index >= 0 && index <= _store.length - 1 && index % 1 === 0) {
      return JSON.parse(atob(_store[index].split('.')[1]))
    }
  }

  return {
    add,
    getStore,
    getLastBlockSignature,
    getBlockData,
  }
}

// const blockchain = JWTBlockchain(<initial jwt>)
// blockchain.add(<next jwt in chain>)

poc.md

Genesis Block (index #0):

The implementation must start with a Genesis Block, which is the block that all other blocks derive from.

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJ2MS4wLjAiLCJpYXQiOjE1Nzk1MTU2MTcsInNpZyI6IiIsImRhdCI6e319.rqmyHA3pgvwSLPS7Arj2pz3KS5rK14ZJNHv3BCAB2b4

{
  "alg": "HS256",
  "typ": "JWT"
}

{
  "iss": "v1.0.0",
  "iat": 1579515617,
  "sig": "",
  "idx": 0,
  "dat": {}
}

Keys

• iss is a Registered Claim, and 'identifies the principal that issued the JWT'. This will enable correct parsing of the dat key below.
• iat is a Registered Claim, and 'identifies the time at which the JWT was issued.'
• sig is the key to the blockchain. It refers to the previous JWT's signature.
• dat is where the data is stored in the chain. Its schema is defined by the version number in the iss key above. An arbitrary JSON payload can be stored, including validation for Proof of Work

Proof of work

A proof-of-work (PoW) system (or protocol, or function) is a consensus mechanism. It deters denial-of-service attacks and other service abuses such as spam on a network by requiring some work from the service requester, usually meaning processing time by a computer. - Wikipedia

With a publicly-distributed ledger, strenuous PoW algorithms should be used (i.e. finding a hash with a specified number of 0 prepending the hash, for example 0000000000000756af69e2ffbdb930261873cd71.