Assigning Each User a Unique 100 character Hash in Ruby on Rails

Question

I have a form on a website that takes in some personal information from the visitor. I\'m passing this information to another service and I need to assign each one of these for

Answer 1

The Ruby standard lib has a module for generating GUIDs:

http://ruby-doc.org/stdlib/libdoc/digest/rdoc/classes/Digest/SHA2.html

Example:

Digest::SHA1.hexdigest(Time.now.to_s)

Answer 2

ActiveSupport::SecureRandom.hex(50)

The chance of this not being unique is astronomical.

Alternate simple "does not scale" race condition fail solution.

class MyModel < ActiveRecord::Base
  before_create :assign_unique_token

  private

  def assign_unique_token
    self.unique_token = ActiveSupport::SecureRandom.hex(50) until unique_token?
  end

  def unique_token?
    self.class.count(:conditions => {:unique_token => unique_token}) == 0
  end
end

If you really want to make sure, make an unique index on the column, and handle a DB uniqueness error by retrying, similar to my implementation above.

Answer 3

If you use a Cipher you can encrypt an always different message to get an always different key:

  def encrypt(data, key, cipher_type)
    aes = OpenSSL::Cipher::Cipher.new(cipher_type)
    aes.encrypt
    aes.key = key
    aes.update(data) + aes.final      
  end

>> Base64.encode64(encrypt(Time.now.to_s, "some_key_long_enough_for_the_job", "AES-256-ECB"))
=> "sKJU3qhszV30Ya9vMFvbqIXus+QygICdDyr7UQFWLeM=\n"