diff --git a/.gitignore b/.gitignore
index 38540f9..bea23a3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,42 @@
-*.DS_Store
+# See https://help.github.com/articles/ignoring-files for more about ignoring files.
+#
+# If you find yourself ignoring temporary files generated by your text editor
+# or operating system, you probably want to add a global ignore instead:
+#   git config --global core.excludesfile '~/.gitignore_global'
+
 *.o
-*.bundle
-Makefile
 test/test_vectors.rb
+
+*.gem
+*.rbc
+/.config
+/.rake_tasks~
+/coverage/
+/InstalledFiles
+/pkg/
+/tmp/
+
+# RSpec configuration and generated files:
+/.rspec
+/spec/examples.txt
+
+# Documentation cache and generated files:
+/.yardoc/
+/_yardoc/
+/doc/
+/rdoc/
+
+# Environment normalization:
+/.bundle/
+/vendor/bundle/*
+!/vendor/bundle/.keep
+/lib/bundler/man/
+
+# For a library or gem, you might want to ignore these files since the code is
+# intended to run in multiple environments; otherwise, check them in:
+/Gemfile.lock
+/.ruby-version
+/.ruby-gemset
+
+# Unless supporting rvm < 1.11.0 or doing something fancy, ignore this:
+.rvmrc
diff --git a/ext/digest/extconf.rb b/ext/digest/extconf.rb
index 4e7bba6..0c2714a 100644
--- a/ext/digest/extconf.rb
+++ b/ext/digest/extconf.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'mkmf'
 
 have_header('ruby/digest.h')
diff --git a/lib/digest/keccak/version.rb b/lib/digest/keccak/version.rb
index c44ebac..6692269 100644
--- a/lib/digest/keccak/version.rb
+++ b/lib/digest/keccak/version.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Digest
   class Keccak
     module Version
diff --git a/test/generate_tests.rb b/test/generate_tests.rb
index 35db2c6..06f19d9 100644
--- a/test/generate_tests.rb
+++ b/test/generate_tests.rb
@@ -1,4 +1,5 @@
 #!/usr/bin/env ruby
+# frozen_string_literal: true
 
 # This will generate a test suite.
 # Based on python-sha3's test suite.
diff --git a/test/test_all.rb b/test/test_all.rb
index 715c85d..4e987e8 100644
--- a/test/test_all.rb
+++ b/test/test_all.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 $LOAD_PATH.unshift(File.expand_path("lib"))
 $LOAD_PATH.unshift(File.expand_path("ext"))
 require 'digest/keccak'
diff --git a/test/test_usage.rb b/test/test_usage.rb
index fddf52d..a18de6a 100644
--- a/test/test_usage.rb
+++ b/test/test_usage.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test/unit'
 
 class KeccakUsageTest < Test::Unit::TestCase