generate proof-of-work tokens
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examples Implemented rarity Jul 6, 2014
lib Implemented rarity Jul 6, 2014
.gitignore Initial commit Jul 5, 2014
index.js Initial commit Jul 5, 2014


generate tokens that prove you did some work.

easily configure the amount of work proven by each token by requiring the target difficulty to be included in the hash.


  var hashcashToken = require('hashcash-token')

  //Generate a token.

  var token = hashcashToken.generate({
    difficulty: 10000, // should take, on average, 10000 hashes to generate a valid token
    data: "woot"

  var isValid = hashcashToken.validate(token);
  console.log(isValid); // true

  // Validate the token using constraints

  hashcashToken.validate(token, {
    difficulty: 20000,
    data: "blerp"
  }) // false

  hashcashToken.validate(token, {
    difficulty: 5000 // minimum difficulty. token difficulty just has to be greater than 5000
  }) // true

  var isRareEnough = hashcashToken.validate(token, {
    rarity: 15000
  }) // true sometimes, false sometimes.


  var hashcashToken = require("hashcash-token")

var token = hashcashToken.generate(opts)

options can be:

  • opts.difficulty - the number of hashes (on average) it should take to generate the token.
  • - the main text body of the token. Maybe you want to issue a challenge token to a user? That'd go here.
  • opts.nonce - if you for some strange reason want to start searching from a certain nonce, you can specify it here.

and will return a token like

    difficulty: 10000,
    data: 'woot',  
    nonce: 5798283827805,
    rarity: 19250.060837947112,
    hash: '0000692aeec5132190df5dcb819ab33590b6a15e46b9348ef41b08758a0d4f5b' 

where the hash is sufficiently low. Note that this is a blocking operation that can potentially take a long time.

  • token.rarity - represents the average number of hashes required to find a hash at least as small as this token's.

var isValid = hashcashToken.validate(token, constraints)

returns true or false


  • constraints.difficulty - the token's difficulty has to be greater than this number.
  • - the token's data must === this. Just a little convenience.
  • constraints.rarity - the token's rarity must be greater than this number.


With npm do:

npm install hashcash-token