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
Methods
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Classes and Modules
Class Public methods
new(secret, options = {})

Source: show | on GitHub 

    # File activesupport/lib/active_support/message_verifier.rb, line 30
30:     def initialize(secret, options = {})
31:       unless options.is_a?(Hash)
32:         ActiveSupport::Deprecation.warn "The second parameter should be an options hash. Use :digest => 'algorithm' to specify the digest algorithm."
33:         options = { :digest => options }
34:       end
35: 
36:       @secret = secret
37:       @digest = options[:digest] || 'SHA1'
38:       @serializer = options[:serializer] || Marshal
39:     end
Instance Public methods
generate(value)

Source: show | on GitHub 

    # File activesupport/lib/active_support/message_verifier.rb, line 52
52:     def generate(value)
53:       data = ::Base64.strict_encode64(@serializer.dump(value))
54:       "#{data}--#{generate_digest(data)}"
55:     end
verify(signed_message)

Source: show | on GitHub 

    # File activesupport/lib/active_support/message_verifier.rb, line 41
41:     def verify(signed_message)
42:       raise InvalidSignature if signed_message.blank?
43: 
44:       data, digest = signed_message.split("--")
45:       if data.present? && digest.present? && secure_compare(digest, generate_digest(data))
46:         @serializer.load(::Base64.decode64(data))
47:       else
48:         raise InvalidSignature
49:       end
50:     end