diff --git a/tools/test_modules/m20720.pm b/tools/test_modules/m20720.pm
new file mode 100644
index 000000000..674d137c6
--- /dev/null
+++ b/tools/test_modules/m20720.pm
@@ -0,0 +1,44 @@
+#!/usr/bin/env perl
+
+##
+## Author......: See docs/credits.txt
+## License.....: MIT
+##
+
+use strict;
+use warnings;
+
+use Digest::SHA  qw (sha256_hex);
+
+sub module_constraints { [[0, 256], [0, 256], [0, 55], [16, 16], [-1, -1]] }
+
+sub module_generate_hash
+{
+  my $word = shift;
+  my $salt = shift;
+
+  my $digest = sha256_hex ($salt . sha256_hex ($word));
+
+  my $hash = sprintf ("%s:%s", $digest, $salt);
+
+  return $hash;
+}
+
+sub module_verify_hash
+{
+  my $line = shift;
+
+  my ($digest, $salt, $word) = split (':', $line);
+
+  return unless defined $digest;
+  return unless defined $salt;
+  return unless defined $word;
+
+  my $word_packed = pack_if_HEX_notation ($word);
+
+  my $new_hash = module_generate_hash ($word_packed, $salt);
+
+  return ($new_hash, $word);
+}
+
+1;