kraken_hmac_signature.rb

require 'httparty'
require 'hashie'
require 'Base64'
require 'addressable/uri'

def post_private(method, opts={}) # Example: post_private('Balance') #=> returns balance info from Kraken, opts not necessary
  opts['nonce'] = nonce
  post_data = encode_options(opts)

  headers = {
    'API-Key' => @api_key,
    'API-Sign' => generate_signature(method, post_data, opts) 
  }

  url = @base_uri + url_path(method)
  r = self.class.post(url, { headers: headers, body: post_data }).parsed_response
  r['error'].empty? ? r['result'] : r['error']
end

def nonce
  Time.now.to_i.to_s.ljust(16,'0')
end

def encode_options(opts)
  uri = Addressable::URI.new
  uri.query_values = opts
  uri.query
end

def generate_signature(method, post_data, opts={})
  key = Base64.decode64(@api_secret)
  message = generate_message(method, opts, post_data)
  generate_hmac(key, message)
end

def generate_message(method, opts, data)
  digest = OpenSSL::Digest.new('sha256', opts['nonce'] + data).digest
  url_path(method) + digest
end

def generate_hmac(key, message)
  Base64.encode64(OpenSSL::HMAC.digest('sha512', key, message)).split.join # to remove '/n' inserted into signature by HMAc
end

def url_path(method)
  '/' + @api_version + '/private/' + method
end