QuickBlox会话创建:Rails应用程序中的意外签名

我正在尝试使用Ruby on Rails从Rest API创建QuickBlox会话。我当前的实施:

def qb_signin_params
  timestamp = Time.now.in_time_zone('UTC').to_i
  nonce = rand.to_s[2..6]
  signature_string = "application_id=#{QuickBlox_Application_Id}&auth_key=#{QUICKBLOX_Authorization_KEY}&nonce=#{nonce}&timestamp=#{timestamp}"
  digest = OpenSSL::Digest.new('sha1')
  signature = OpenSSL::HMAC.hexdigest(digest, signature_string, QUICKBLOX_Authorization_SECRET)

  params = Hash.new
  params['application_id'] = QuickBlox_Application_Id
  params['auth_key'] = QUICKBLOX_Authorization_KEY
  params['timestamp'] = timestamp
  params['nonce'] = nonce
  params['signature'] = signature

  params
end

返回以下错误:

unexpected token at '<?xml version="1.0" encoding="UTF-8"?>
<errors> 
  <error>Unexpected signature</error>
</errors>

我已经搜索了好几个地方,但始终找不到Ruby的正确Signature生成。请帮忙。