Decrypt session

decrypt_session.rb

# Rails 4.2.7

salt         = "encrypted cookie"         
signed_salt  = "signed encrypted cookie"  

key_generator = Rails.application.key_generator
secret = key_generator.generate_key(salt)
sign_secret = key_generator.generate_key(signed_salt)
digest = Rails.application.config.action_dispatch.cookies_digest || "SHA1"

encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, digest: digest, serializer: ActiveSupport::MessageEncryptor::NullSerializer)

cookie = 'your cookie'

puts encryptor.decrypt_and_verify(cookie)