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 attribute to something that responds to dump and load, e.g.:

@verifier.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 30
def initialize(secret, options = {})
  unless options.is_a?(Hash)
    ActiveSupport::Deprecation.warn "The second parameter should be an options hash. Use :digest => 'algorithm' to specify the digest algorithm."
    options = { :digest => options }
  end

  @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 52
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 41
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))
    @serializer.load(::Base64.decode64(data))
  else
    raise InvalidSignature
  end
end