diff --git a/2016/ruby/day_05.rb b/2016/ruby/day_05.rb
new file mode 100644
index 0000000..7420737
--- /dev/null
+++ b/2016/ruby/day_05.rb
@@ -0,0 +1,22 @@
+require 'digest/md5'
+
+door_id = 'wtnhxymk'
+password = Array.new(8, nil)
+
+VALID = (0..7).map(&:to_s).to_a
+
+index = 0
+while password.any?(&:nil?)
+  puts index if index % 1000000 == 0
+  hash = Digest::MD5.hexdigest("#{door_id}#{index}")
+  if hash.start_with?('00000')
+    i = hash[5]
+    if VALID.include?(i) && password[i.to_i].nil?
+      password[i.to_i] = hash[6]
+      p hash, password
+    end
+  end
+  index += 1
+end
+
+puts password.join