MessageVerifier makes it easy to generate and verify messages which are signed to prevent tampering.

This is useful for cases like remember-me tokens and auto-unsubscribe links where the session store isn't suitable or available.

Remember Me:

cookies[:remember_me] = @verifier.generate([@user.id, 2.weeks.from_now])

In the authentication filter:

id, time = @verifier.verify(cookies[:remember_me])
if time < Time.now
  self.current_user = User.find(id)
end

By default it uses Marshal to serialize the message. If you want to use another serialization method, you can set the serializer in the options hash upon initialization:

@verifier = ActiveSupport::MessageVerifier.new('s3Krit', serializer: YAML)
Namespace
Methods
G
N
V
Class Public methods
new(secret, options = {})

Source: show | on GitHub 

# File activesupport/lib/active_support/message_verifier.rb, line 29
def initialize(secret, options = {})
  @secret = secret
  @digest = options[:digest] || 'SHA1'
  @serializer = options[:serializer] || Marshal
end
Instance Public methods
generate(value)

Source: show | on GitHub 

# File activesupport/lib/active_support/message_verifier.rb, line 51
def generate(value)
  data = ::Base64.strict_encode64(@serializer.dump(value))
  "#{data}--#{generate_digest(data)}"
end
verify(signed_message)

Source: show | on GitHub 

# File activesupport/lib/active_support/message_verifier.rb, line 35
def verify(signed_message)
  raise InvalidSignature if signed_message.blank?

  data, digest = signed_message.split("--")
  if data.present? && digest.present? && secure_compare(digest, generate_digest(data))
    begin
      @serializer.load(::Base64.strict_decode64(data))
    rescue ArgumentError => argument_error
      raise InvalidSignature if argument_error.message =~ %r{invalid base64}
      raise
    end
  else
    raise InvalidSignature
  end
end