diff --git a/kenna_kdi_importer/subdomain_generator.rb b/kenna_kdi_importer/subdomain_generator.rb
new file mode 100644
index 0000000..17ccdc7
--- /dev/null
+++ b/kenna_kdi_importer/subdomain_generator.rb
@@ -0,0 +1,24 @@
+module KennaKdi
+  class SubdomainGenerator
+    attr_accessor :tld, :base_domain
+
+    def initialize(tld, base_domain)
+      @tld = tld
+      @base_domain = base_domain
+    end
+
+    def perform(year, month, day)
+      # generating a subdomain.
+      # https://en.wikipedia.org/wiki/Domain_generation_algorithm
+      domain = ""
+
+      16.times do
+        year = ((year ^ 8 * year) >> 11) ^ ((year & 0xFFFFFFF0) << 17)
+        month = ((month ^ 4 * month) >> 25) ^ 16 * (month & 0xFFFFFFF8)
+        day = ((day ^ (day << 13)) >> 19) ^ ((day & 0xFFFFFFFE) << 12)
+        domain += (((year ^ month ^ day) % 25) + 97).chr
+      end
+      domain + base_domain + tld
+    end
+  end
+end