diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 0000000..b18fd29
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: 'github-actions'
+    directory: '/'
+    schedule:
+      interval: 'weekly'
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
new file mode 100644
index 0000000..1905ff8
--- /dev/null
+++ b/.github/workflows/release.yml
@@ -0,0 +1,66 @@
+name: Publish gem to rubygems.org
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+permissions:
+  contents: read
+
+jobs:
+  push:
+    if: github.repository == 'bcrypt-ruby/bcrypt-ruby'
+    runs-on: ubuntu-latest
+
+    environment:
+      name: rubygems.org
+      url: https://rubygems.org/gems/bcrypt
+
+    permissions:
+      contents: write
+      id-token: write
+
+    strategy:
+      matrix:
+        ruby: ["ruby", "jruby"]
+
+    steps:
+      - name: Harden Runner
+        uses: step-security/harden-runner@v2
+        with:
+          egress-policy: audit
+
+      - uses: actions/checkout@v6
+
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+
+        # https://github.com/rubygems/rubygems/issues/5882
+      - name: Install dependencies and build for JRuby
+        run: |
+          sudo apt install default-jdk maven
+          gem update --system
+          gem install ruby-maven rake-compiler --no-document
+        if: matrix.ruby == 'jruby'
+
+      - name: Install dependencies
+        run: bundle install --jobs 4 --retry 3
+
+      - name: Compile on JRuby
+        run: |
+          rake compile
+        if: matrix.ruby == 'jruby'
+
+      - name: Publish to RubyGems
+        uses: rubygems/release-gem@v1
+
+      - name: Create GitHub release
+        run: |
+          tag_name="$(git describe --tags --abbrev=0)"
+          gh release create "${tag_name}" --verify-tag --generate-notes
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        if: matrix.ruby != 'jruby'
diff --git a/.github/workflows/ruby.yml b/.github/workflows/ruby.yml
new file mode 100644
index 0000000..f0f2e10
--- /dev/null
+++ b/.github/workflows/ruby.yml
@@ -0,0 +1,56 @@
+name: Test Suite
+
+# Run against all commits and pull requests.
+on: [ push, pull_request ]
+
+env:
+  JAVA_OPTS: '-Xms60M -Xmx1G'
+
+jobs:
+  ruby-versions:
+    uses: ruby/actions/.github/workflows/ruby_versions.yml@master
+    with:
+      engine: cruby
+      min_version: 3.1
+
+  test:
+    needs: ruby-versions
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        ruby: ${{ fromJson(needs.ruby-versions.outputs.versions) }}
+        os: [ ubuntu-latest, macos-latest, windows-latest ]
+        include:
+          - { os: windows-latest, ruby: jruby-head }
+          - { os: macos-latest, ruby: jruby-head }
+          - { os: ubuntu-latest, ruby: jruby-head }
+          - { os: windows-latest, ruby: ucrt }
+          - { os: windows-latest, ruby: mingw }
+          - { os: macos-latest, ruby: truffleruby }
+          - { os: ubuntu-latest, ruby: truffleruby }
+          - { os: macos-latest, ruby: truffleruby-head }
+          - { os: ubuntu-latest, ruby: truffleruby-head }
+
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Set up Ruby
+        uses: ruby/setup-ruby-pkgs@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+          apt-get: "haveged libyaml-dev"
+          brew: libyaml
+          vcpkg: libyaml
+
+      - name: Set JRuby ENV vars
+        run: |
+          echo 'JAVA_OPTS=-Xmx1g' >> $GITHUB_ENV
+        if: ${{ ! startsWith(matrix.ruby, 'jruby') }}
+
+      - name: Install dependencies
+        run: bundle install --jobs 1
+
+      - name: Run tests
+        run: bundle exec rake
+        continue-on-error: ${{ matrix.ruby == 'jruby-head' }}
diff --git a/.gitignore b/.gitignore
index 3c40c7f..633ad7c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,3 +7,4 @@ tmp
 *.jar
 .DS_Store
 .rbenv-gemsets
+Gemfile.lock
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 621ca7f..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,17 +0,0 @@
-language: ruby
-before_install:
-  - "echo 'gem: --no-rdoc --no-ri' > ~/.gemrc"
-  - gem update --system 2.7.8
-  - gem install bundler -v 1.17.3
-rvm:
-  - 2.0
-  - 2.1
-  - 2.2
-  - 2.3
-  - 2.4
-  - 2.5
-  - 2.6
-  - ruby-head
-  - jruby-head
-  - rbx-3
-script: bundle exec rake
diff --git a/CHANGELOG b/CHANGELOG
index 8bead60..a2c9982 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,94 +1,127 @@
-1.0.0  Feb 27 2007
- - Initial release.
+3.1.22 Mar 18 2026
+  - [CVE-2026-33306] Fix integer overflow in Java extension
 
-2.0.0  Mar 07 2007
- - Removed BCrypt::Password#exactly_equals -- use BCrypt::Password#eql? instead.
- - Added BCrypt::Password#is_password?.
- - Refactored out BCrypt::Internals into more useful BCrypt::Engine.
- - Added validation of secrets -- nil is not healthy.
+3.1.21 Dec 31 2025
+  - Use constant time comparisons
+  - Mark as Ractor safe
 
-2.0.1  Mar 09 2007
- - Fixed load path issues
- - Fixed crashes when hashing weird values (e.g., false, etc.)
+3.1.20 Nov 17 2023
+  - Limit packaged files -- decrease gem filesize by ~28% [GH #272 by @pusewicz]
 
-2.0.2  Jun 06 2007
- - Fixed example code in the README [Winson]
- - Fixed Solaris compatibility [Jeremy LaTrasse, Twitter crew]
+3.1.19 June 22 2023
+  - Deprecate passing the third argument to `BCrypt::Engine.hash_secret` [GH #207 by @sergey-alekseev]
+  - Add GC guards so the C compiler won't optimize out references [GH #270]
 
-2.0.3  May 07 2008
- - Made exception classes descend from StandardError, not Exception [Dan42]
- - Changed BCrypt::Engine.hash to BCrypt::Engine.hash_secret to avoid Merb
-   sorting issues. [Lee Pope]
+3.1.18 May 16 2022
+  - Unlock GVL when calculating hashes and salts [GH #260]
+  - Fix compilation warnings in `ext/mri/bcrypt_ext.c` [GH #261]
 
-2.0.4  Mar 09 2009
-  - Added Ruby 1.9 compatibility. [Genki Takiuchi]
-  - Fixed segfaults on some different types of empty strings. [Mike Pomraning]
+3.1.17 Mar 14 2022
+- Fix regex in validators to use \A and \z instead of ^ and $ [GH #121]
+- Truncate secrets greater than 72 bytes in hash_secret [GH #255]
+- Assorted test and doc improvements
 
-2.0.5  Mar 11 2009
-  - Fixed Ruby 1.8.5 compatibility. [Mike Pomraning]
+3.1.16 Sep 3 2020
+  - Fix compilation on FreeBSD. [GH #234]
 
-2.1.0  Aug 12 2009
-  - Improved code coverage, unit tests, and build chain. [Hongli Lai]
-  - Ruby 1.9 compatibility fixes. [Hongli Lai]
-  - JRuby support, using Damien Miller's jBCrypt. [Hongli Lai]
-  - Ruby 1.9 GIL releasing for high-cost hashes. [Hongli Lai]
+3.1.15 July 21 2020
+  - Remove GVL optimization.  Apparently it breaks things [GH #230]
 
-2.1.1  Aug 14 2009
-  - JVM 1.4/1.5 compatibility [Hongli Lai]
+3.1.14 July 21 2020
+  - Start calibration from the minimum cost supported by the algorithm [GH #206 by @sergey-alekseev]
 
-2.1.2  Sep 16 2009
-  - Fixed support for Solaris, OpenSolaris.
+3.1.13 May 31 2019
+  - No longer include compiled binaries for Windows. See GH #173.
+  - Update C and Java implementations to latest versions [GH #182 by @fonica]
+  - Bump default cost to 12 [GH #181 by @bdewater]
+  - Remove explicit support for Rubies 1.8 and 1.9
+  - Define SKIP_GNU token when building extension (Fixes FreeBSD >= 12) [GH #189 by @adam12]
 
-3.0.0  Aug 24 2011
-  - Bcrypt C implementation replaced with a public domain implementation.
-  - License changed to MIT
+3.1.12 May 16 2018
+  - Add support for Ruby 2.3, 2.4, and 2.5 in compiled Windows binaries
+  - Fix compatibility with libxcrypt - Fixes hash errors in Fedora 28 and Ubuntu 20 [GH #164 by @besser82]
 
-3.0.1  Sep 12 2011
-  - create raises an exception if the cost is higher than 31. GH #27
+3.1.11 Mar 06 2016
+  - Add support for Ruby 2.2 in compiled Windows binaries
 
-3.1.0  May 07 2013
-  - Add BCrypt::Password.valid_hash?(str) to check if a string is a valid bcrypt password hash
-  - BCrypt::Password cost should be set to DEFAULT_COST if nil
-  - Add BCrypt::Engine.cost attribute for getting/setting a default cost externally
+3.1.10 Jan 28 2015
+  - Fix issue with dumping a BCrypt::Password instance to YAML in Ruby 2.2 [GH #107 by @mattwildig]
 
-3.1.1  Jul 10 2013
-  - Remove support for Ruby 1.8 in compiled win32 binaries
+3.1.9  Oct 23 2014
+  - Rebuild corrupt binaries
 
-3.1.2  Aug 26 2013
-  - Add support for Ruby 1.8 and 2.0 (in addition to 1.9) in compiled Windows binaries
-  - Add support for 64-bit Windows
+3.1.8  Oct 23 2014
+  - Add support for Ruby 2.1 in compiled Windows binaries [GH #102]
 
-3.1.3  Feb 21 2014
-  - Add support for Ruby 2.1 in compiled Windows binaries
-  - Rename gem from "bcrypt-ruby" to just "bcrypt". [GH #86 by @sferik]
+3.1.7  Feb 24 2014
+  - Rebuild corrupt Java binary version of gem [GH #90]
+  - The 2.1 support for Windows binaries alleged in 3.1.3 was a lie -- documentation removed
 
 3.1.6  Feb 21 2014
   - Dummy version of "bcrypt-ruby" needed a couple version bumps to fix some
     bugs. It felt wrong to have that at a higher version than the real gem, so
     the real gem is getting bumped to 3.1.6.
 
-3.1.7  Feb 24 2014
-  - Rebuild corrupt Java binary version of gem [GH #90]
-  - The 2.1 support for Windows binaries alleged in 3.1.3 was a lie -- documentation removed
+3.1.3  Feb 21 2014
+  - Add support for Ruby 2.1 in compiled Windows binaries
+  - Rename gem from "bcrypt-ruby" to just "bcrypt". [GH #86 by @sferik]
 
-3.1.8  Oct 23 2014
-  - Add support for Ruby 2.1 in compiled Windows binaries [GH #102]
+3.1.2  Aug 26 2013
+  - Add support for Ruby 1.8 and 2.0 (in addition to 1.9) in compiled Windows binaries
+  - Add support for 64-bit Windows
 
-3.1.9  Oct 23 2014
-  - Rebuild corrupt binaries
+3.1.1  Jul 10 2013
+  - Remove support for Ruby 1.8 in compiled win32 binaries
 
-3.1.10 Jan 28 2015
-  - Fix issue with dumping a BCrypt::Password instance to YAML in Ruby 2.2 [GH #107 by @mattwildig]
+3.1.0  May 07 2013
+  - Add BCrypt::Password.valid_hash?(str) to check if a string is a valid bcrypt password hash
+  - BCrypt::Password cost should be set to DEFAULT_COST if nil
+  - Add BCrypt::Engine.cost attribute for getting/setting a default cost externally
 
-3.1.11 Mar 06 2016
-  - Add support for Ruby 2.2 in compiled Windows binaries
+3.0.1  Sep 12 2011
+  - create raises an exception if the cost is higher than 31. GH #27
 
-3.1.12 May 16 2018
-  - Add support for Ruby 2.3, 2.4, and 2.5 in compiled Windows binaries
-  - Fix compatibility with libxcrypt [GH #164 by @besser82]
+3.0.0  Aug 24 2011
+  - Bcrypt C implementation replaced with a public domain implementation.
+  - License changed to MIT
 
-[DRAFT] 4.0.0 MMM DD YYYY
-  - No longer include compiled binaries for Windows. See GH #173.
-  - Update C and Java implementations to latest versions [GH #182 by @fonica]
-  - Bump default cost to 12 [GH #181 by @bdewater]
-  - Remove explicit support for Rubies 1.8 and 1.9
+2.1.2  Sep 16 2009
+  - Fixed support for Solaris, OpenSolaris.
+
+2.1.1  Aug 14 2009
+  - JVM 1.4/1.5 compatibility [Hongli Lai]
+
+2.1.0  Aug 12 2009
+  - Improved code coverage, unit tests, and build chain. [Hongli Lai]
+  - Ruby 1.9 compatibility fixes. [Hongli Lai]
+  - JRuby support, using Damien Miller's jBCrypt. [Hongli Lai]
+  - Ruby 1.9 GIL releasing for high-cost hashes. [Hongli Lai]
+
+2.0.5  Mar 11 2009
+  - Fixed Ruby 1.8.5 compatibility. [Mike Pomraning]
+
+2.0.4  Mar 09 2009
+  - Added Ruby 1.9 compatibility. [Genki Takiuchi]
+  - Fixed segfaults on some different types of empty strings. [Mike Pomraning]
+
+2.0.3  May 07 2008
+ - Made exception classes descend from StandardError, not Exception [Dan42]
+ - Changed BCrypt::Engine.hash to BCrypt::Engine.hash_secret to avoid Merb
+   sorting issues. [Lee Pope]
+
+2.0.2  Jun 06 2007
+ - Fixed example code in the README [Winson]
+ - Fixed Solaris compatibility [Jeremy LaTrasse, Twitter crew]
+
+2.0.1  Mar 09 2007
+ - Fixed load path issues
+ - Fixed crashes when hashing weird values (e.g., false, etc.)
+
+2.0.0  Mar 07 2007
+ - Removed BCrypt::Password#exactly_equals -- use BCrypt::Password#eql? instead.
+ - Added BCrypt::Password#is_password?.
+ - Refactored out BCrypt::Internals into more useful BCrypt::Engine.
+ - Added validation of secrets -- nil is not healthy.
+
+1.0.0  Feb 27 2007
+ - Initial release.
diff --git a/Gemfile.lock b/Gemfile.lock
deleted file mode 100644
index 9981158..0000000
--- a/Gemfile.lock
+++ /dev/null
@@ -1,37 +0,0 @@
-PATH
-  remote: .
-  specs:
-    bcrypt (3.1.13)
-
-GEM
-  remote: https://rubygems.org/
-  specs:
-    diff-lcs (1.3)
-    rake (12.3.2)
-    rake-compiler (0.9.9)
-      rake
-    rspec (3.8.0)
-      rspec-core (~> 3.8.0)
-      rspec-expectations (~> 3.8.0)
-      rspec-mocks (~> 3.8.0)
-    rspec-core (3.8.0)
-      rspec-support (~> 3.8.0)
-    rspec-expectations (3.8.3)
-      diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.8.0)
-    rspec-mocks (3.8.0)
-      diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.8.0)
-    rspec-support (3.8.0)
-
-PLATFORMS
-  java
-  ruby
-
-DEPENDENCIES
-  bcrypt!
-  rake-compiler (~> 0.9.2)
-  rspec (>= 3)
-
-BUNDLED WITH
-   1.16.1
diff --git a/README.md b/README.md
index 9bbc739..88598ad 100644
--- a/README.md
+++ b/README.md
@@ -2,11 +2,9 @@
 
 An easy way to keep your users' passwords secure.
 
-* https://github.com/codahale/bcrypt-ruby/tree/master
-
-[![Travis Build Status](https://travis-ci.org/codahale/bcrypt-ruby.svg?branch=master)](https://travis-ci.org/codahale/bcrypt-ruby)
-[![AppVeyor Build Status](https://ci.appveyor.com/api/projects/status/6fplerx9lnaf0hyo?svg=true)](https://ci.appveyor.com/project/TJSchuck35975/bcrypt-ruby)
+* https://github.com/bcrypt-ruby/bcrypt-ruby/tree/master
 
+[![Github Actions Build Status](https://github.com/bcrypt-ruby/bcrypt-ruby/actions/workflows/ruby.yml/badge.svg?branch=master)](https://github.com/bcrypt-ruby/bcrypt-ruby/actions/workflows/ruby.yml)
 
 ## Why you should use `bcrypt()`
 
@@ -32,8 +30,8 @@ re-hash those passwords. This vulnerability only affected the JRuby gem.
 The bcrypt gem is available on the following Ruby platforms:
 
 * JRuby
-* RubyInstaller 2.0 – 2.5 builds on Windows with the DevKit
-* Any 2.0 – 2.5 Ruby on a BSD/OS X/Linux system with a compiler
+* RubyInstaller builds on Windows with the DevKit
+* Any modern Ruby on a BSD/OS X/Linux system with a compiler
 
 ## How to use `bcrypt()` in your Rails application
 
diff --git a/Rakefile b/Rakefile
index 98ed63b..95e22a5 100644
--- a/Rakefile
+++ b/Rakefile
@@ -5,6 +5,8 @@ require 'rake/javaextensiontask'
 require 'rake/clean'
 require 'rdoc/task'
 require 'benchmark'
+require "bundler"
+Bundler::GemHelper.install_tasks
 
 CLEAN.include(
   "tmp",
@@ -50,6 +52,8 @@ end
 if RUBY_PLATFORM =~ /java/
   Rake::JavaExtensionTask.new('bcrypt_ext', GEMSPEC) do |ext|
     ext.ext_dir = 'ext/jruby'
+    ext.source_version = "1.8"
+    ext.target_version = "1.8"
   end
 else
   Rake::ExtensionTask.new("bcrypt_ext", GEMSPEC) do |ext|
diff --git a/appveyor.yml b/appveyor.yml
deleted file mode 100644
index e832e22..0000000
--- a/appveyor.yml
+++ /dev/null
@@ -1,50 +0,0 @@
-version: "{branch}-{build}"
-build: off
-clone_depth: 1
-
-init:
-  # Install Ruby head
-  - if %RUBY_VERSION%==head (
-      appveyor DownloadFile https://github.com/oneclick/rubyinstaller2/releases/download/rubyinstaller-head/rubyinstaller-head-x86.exe -FileName C:\head_x86.exe &
-      C:\head_x86.exe /verysilent /dir=C:\Ruby%RUBY_VERSION%
-    )
-  - if %RUBY_VERSION%==head-x64 (
-      appveyor DownloadFile https://github.com/oneclick/rubyinstaller2/releases/download/rubyinstaller-head/rubyinstaller-head-x64.exe -FileName C:\head_x64.exe &
-      C:\head_x64.exe /verysilent /dir=C:\Ruby%RUBY_VERSION%
-    )
-
-  # Add Ruby to the path
-  - set PATH=C:\Ruby%RUBY_VERSION%\bin;%PATH%
-
-environment:
-  matrix:
-    - RUBY_VERSION: "head"
-    - RUBY_VERSION: "head-x64"
-    - RUBY_VERSION: "25"
-    - RUBY_VERSION: "25-x64"
-    - RUBY_VERSION: "24"
-    - RUBY_VERSION: "24-x64"
-    - RUBY_VERSION: "23"
-    - RUBY_VERSION: "23-x64"
-    - RUBY_VERSION: "22"
-    - RUBY_VERSION: "22-x64"
-    - RUBY_VERSION: "21"
-    - RUBY_VERSION: "21-x64"
-    - RUBY_VERSION: "200"
-    - RUBY_VERSION: "200-x64"
-
-install:
-  - ps: "Set-Content -Value 'gem: --no-ri --no-rdoc ' -Path C:\\ProgramData\\gemrc"
-  - if %RUBY_VERSION%==head     ( gem install bundler -v'< 2' )
-  - if %RUBY_VERSION%==head-x64 ( gem install bundler -v'< 2' )
-  - bundle install
-
-before_build:
-  - ruby -v
-  - gem -v
-
-build_script:
-  - bundle exec rake compile -rdevkit
-
-test_script:
-  - bundle exec rake spec
diff --git a/bcrypt.gemspec b/bcrypt.gemspec
index e67bad2..b848c01 100644
--- a/bcrypt.gemspec
+++ b/bcrypt.gemspec
@@ -1,6 +1,6 @@
 Gem::Specification.new do |s|
   s.name = 'bcrypt'
-  s.version = '3.1.13'
+  s.version = '3.1.22'
 
   s.summary = "OpenBSD's bcrypt() password hashing algorithm."
   s.description = <<-EOF
@@ -9,11 +9,13 @@ Gem::Specification.new do |s|
     passwords.
   EOF
 
-  s.files = `git ls-files`.split("\n")
+  s.files = Dir['CHANGELOG', 'COPYING', 'README.md', 'lib/**/*.rb', 'ext/**/*.*']
   s.require_path = 'lib'
 
-  s.add_development_dependency 'rake-compiler', '~> 0.9.2'
+  s.add_development_dependency 'rake-compiler', '~> 1.2.0'
   s.add_development_dependency 'rspec', '>= 3'
+  s.add_development_dependency 'rdoc', '>= 7.0.3'
+  s.add_development_dependency 'benchmark', '>= 0.5.0'
 
   s.rdoc_options += ['--title', 'bcrypt-ruby', '--line-numbers', '--inline-source', '--main', 'README.md']
   s.extra_rdoc_files += ['README.md', 'COPYING', 'CHANGELOG', *Dir['lib/**/*.rb']]
@@ -22,6 +24,8 @@ Gem::Specification.new do |s|
 
   s.authors = ["Coda Hale"]
   s.email = "coda.hale@gmail.com"
-  s.homepage = "https://github.com/codahale/bcrypt-ruby"
+  s.homepage = "https://github.com/bcrypt-ruby/bcrypt-ruby"
   s.license = "MIT"
+
+  s.metadata["changelog_uri"] = s.homepage + "/blob/master/CHANGELOG"
 end
diff --git a/ext/jruby/bcrypt_jruby/BCrypt.java b/ext/jruby/bcrypt_jruby/BCrypt.java
index 86db91b..bf987d9 100644
--- a/ext/jruby/bcrypt_jruby/BCrypt.java
+++ b/ext/jruby/bcrypt_jruby/BCrypt.java
@@ -688,20 +688,21 @@ static long roundsForLogRounds(int log_rounds) {
 	 */
 	private byte[] crypt_raw(byte password[], byte salt[], int log_rounds,
 							boolean sign_ext_bug, int safety) {
-		int rounds, i, j;
+		long rounds;
+		int i, j;
 		int cdata[] =  bf_crypt_ciphertext.clone();
 		int clen = cdata.length;
 		byte ret[];
 
 		if (log_rounds < 4 || log_rounds > 31)
 			throw new IllegalArgumentException ("Bad number of rounds");
-		rounds = 1 << log_rounds;
+		rounds = roundsForLogRounds(log_rounds);
 		if (salt.length != BCRYPT_SALT_LEN)
 			throw new IllegalArgumentException ("Bad salt length");
 
 		init_key();
 		ekskey(salt, password, sign_ext_bug, safety);
-		for (i = 0; i < rounds; i++) {
+		for (long r = 0; r < rounds; r++) {
 			key(password, sign_ext_bug, safety);
 			key(salt, false, safety);
 		}
diff --git a/ext/mri/bcrypt_ext.c b/ext/mri/bcrypt_ext.c
index b2edd1d..3e5ac1c 100644
--- a/ext/mri/bcrypt_ext.c
+++ b/ext/mri/bcrypt_ext.c
@@ -1,59 +1,120 @@
 #include <ruby.h>
 #include <ow-crypt.h>
 
+#ifdef HAVE_RUBY_THREAD_H
+#include <ruby/thread.h>
+#endif
+
 static VALUE mBCrypt;
 static VALUE cBCryptEngine;
 
+struct bc_salt_args {
+    const char * prefix;
+    unsigned long count;
+    const char * input;
+    int size;
+};
+
+static void * bc_salt_nogvl(void * ptr) {
+    struct bc_salt_args * args = ptr;
+
+    return crypt_gensalt_ra(args->prefix, args->count, args->input, args->size);
+}
+
 /* Given a logarithmic cost parameter, generates a salt for use with +bc_crypt+.
 */
 static VALUE bc_salt(VALUE self, VALUE prefix, VALUE count, VALUE input) {
     char * salt;
     VALUE str_salt;
-
-    salt = crypt_gensalt_ra(
-	    StringValuePtr(prefix),
-	    NUM2ULONG(count),
-	    NIL_P(input) ? NULL : StringValuePtr(input),
-	    NIL_P(input) ? 0 : RSTRING_LEN(input));
+    struct bc_salt_args args;
+
+    /* duplicate the parameters for thread safety.  If another thread has a
+     * reference to the parameters and mutates them while we are working,
+     * that would be very bad.  Duping the strings means that the reference
+     * isn't shared. */
+    prefix = rb_str_new_frozen(prefix);
+    input  = rb_str_new_frozen(input);
+
+    args.prefix = StringValueCStr(prefix);
+    args.count  = NUM2ULONG(count);
+    args.input  = NIL_P(input) ? NULL : StringValuePtr(input);
+    args.size   = NIL_P(input) ? 0 : RSTRING_LEN(input);
+
+#ifdef HAVE_RUBY_THREAD_H
+    salt = rb_thread_call_without_gvl(bc_salt_nogvl, &args, NULL, NULL);
+#else
+    salt = bc_salt_nogvl((void *)&args);
+#endif
 
     if(!salt) return Qnil;
 
     str_salt = rb_str_new2(salt);
-    xfree(salt);
+
+    RB_GC_GUARD(prefix);
+    RB_GC_GUARD(input);
+    free(salt);
 
     return str_salt;
 }
 
+struct bc_crypt_args {
+    const char * key;
+    const char * setting;
+    void * data;
+    int size;
+};
+
+static void * bc_crypt_nogvl(void * ptr) {
+    struct bc_crypt_args * args = ptr;
+
+    return crypt_ra(args->key, args->setting, &args->data, &args->size);
+}
+
 /* Given a secret and a salt, generates a salted hash (which you can then store safely).
 */
 static VALUE bc_crypt(VALUE self, VALUE key, VALUE setting) {
     char * value;
-    void * data;
-    int size;
     VALUE out;
 
-    data = NULL;
-    size = 0xDEADBEEF;
+    struct bc_crypt_args args;
 
     if(NIL_P(key) || NIL_P(setting)) return Qnil;
 
-    value = crypt_ra(
-	    NIL_P(key) ? NULL : StringValuePtr(key),
-	    NIL_P(setting) ? NULL : StringValuePtr(setting),
-	    &data,
-	    &size);
+    /* duplicate the parameters for thread safety.  If another thread has a
+     * reference to the parameters and mutates them while we are working,
+     * that would be very bad.  Duping the strings means that the reference
+     * isn't shared. */
+    key     = rb_str_new_frozen(key);
+    setting = rb_str_new_frozen(setting);
+
+    args.data    = NULL;
+    args.size    = 0xDEADBEEF;
+    args.key     = NIL_P(key)     ? NULL : StringValueCStr(key);
+    args.setting = NIL_P(setting) ? NULL : StringValueCStr(setting);
+
+#ifdef HAVE_RUBY_THREAD_H
+    value = rb_thread_call_without_gvl(bc_crypt_nogvl, &args, NULL, NULL);
+#else
+    value = bc_crypt_nogvl((void *)&args);
+#endif
 
-    if(!value) return Qnil;
+    if(!value || !args.data) return Qnil;
 
     out = rb_str_new2(value);
 
-    xfree(data);
+    RB_GC_GUARD(key);
+    RB_GC_GUARD(setting);
+    free(args.data);
 
     return out;
 }
 
 /* Create the BCrypt and BCrypt::Engine modules, and populate them with methods. */
 void Init_bcrypt_ext(){
+#ifdef HAVE_RB_EXT_RACTOR_SAFE
+    rb_ext_ractor_safe(true);
+#endif
+    
     mBCrypt = rb_define_module("BCrypt");
     cBCryptEngine = rb_define_class_under(mBCrypt, "Engine", rb_cObject);
 
diff --git a/ext/mri/crypt_blowfish.c b/ext/mri/crypt_blowfish.c
index 9d3f3be..5760064 100644
--- a/ext/mri/crypt_blowfish.c
+++ b/ext/mri/crypt_blowfish.c
@@ -361,7 +361,7 @@ static BF_ctx BF_init_state = {
 	}
 };
 
-static unsigned char BF_itoa64[64 + 1] =
+static const unsigned char BF_itoa64[64 + 1] =
 	"./ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
 
 static unsigned char BF_atoi64[0x60] = {
@@ -387,9 +387,8 @@ static int BF_decode(BF_word *dst, const char *src, int size)
 	unsigned char *dptr = (unsigned char *)dst;
 	unsigned char *end = dptr + size;
 	const unsigned char *sptr = (const unsigned char *)src;
-	unsigned int tmp, c1, c2, c3, c4;
-
 	do {
+		unsigned int tmp, c1, c2, c3, c4;
 		BF_safe_atoi64(c1, *sptr++);
 		BF_safe_atoi64(c2, *sptr++);
 		*dptr++ = (c1 << 2) | ((c2 & 0x30) >> 4);
@@ -402,7 +401,6 @@ static int BF_decode(BF_word *dst, const char *src, int size)
 		BF_safe_atoi64(c4, *sptr++);
 		*dptr++ = ((c3 & 0x03) << 6) | c4;
 	} while (dptr < end);
-
 	return 0;
 }
 
@@ -411,9 +409,8 @@ static void BF_encode(char *dst, const BF_word *src, int size)
 	const unsigned char *sptr = (const unsigned char *)src;
 	const unsigned char *end = sptr + size;
 	unsigned char *dptr = (unsigned char *)dst;
-	unsigned int c1, c2;
-
 	do {
+		unsigned int c1, c2;
 		c1 = *sptr++;
 		*dptr++ = BF_itoa64[c1 >> 2];
 		c1 = (c1 & 0x03) << 4;
@@ -442,10 +439,9 @@ static void BF_swap(BF_word *x, int count)
 {
 	static int endianness_check = 1;
 	char *is_little_endian = (char *)&endianness_check;
-	BF_word tmp;
-
 	if (*is_little_endian)
 	do {
+		BF_word tmp;
 		tmp = *x;
 		tmp = (tmp << 16) | (tmp >> 16);
 		*x++ = ((tmp & 0x00FF00FF) << 8) | ((tmp >> 8) & 0x00FF00FF);
@@ -517,7 +513,7 @@ static void BF_swap(BF_word *x, int count)
 	R = L; \
 	L = tmp4 ^ data.ctx.P[BF_N + 1];
 
-#if BF_ASM
+#if BF_ASM == 1
 #define BF_body() \
 	_BF_body_r(&data.ctx);
 #else
@@ -650,7 +646,7 @@ static char *BF_crypt(const char *key, const char *setting,
 	char *output, int size,
 	BF_word min)
 {
-#if BF_ASM
+#if BF_ASM == 1
 	extern void _BF_body_r(BF_ctx *ctx);
 #endif
 	struct {
diff --git a/ext/mri/crypt_gensalt.c b/ext/mri/crypt_gensalt.c
index 73c15a1..744912a 100644
--- a/ext/mri/crypt_gensalt.c
+++ b/ext/mri/crypt_gensalt.c
@@ -28,7 +28,7 @@
 /* Just to make sure the prototypes match the actual definitions */
 #include "crypt_gensalt.h"
 
-unsigned char _crypt_itoa64[64 + 1] =
+const unsigned char _crypt_itoa64[64 + 1] =
 	"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
 
 char *_crypt_gensalt_traditional_rn(const char *prefix, unsigned long count,
diff --git a/ext/mri/crypt_gensalt.h b/ext/mri/crypt_gensalt.h
index 457bbfe..3a5ca08 100644
--- a/ext/mri/crypt_gensalt.h
+++ b/ext/mri/crypt_gensalt.h
@@ -17,7 +17,7 @@
 #ifndef _CRYPT_GENSALT_H
 #define _CRYPT_GENSALT_H
 
-extern unsigned char _crypt_itoa64[];
+extern const unsigned char _crypt_itoa64[];
 extern char *_crypt_gensalt_traditional_rn(const char *prefix,
 	unsigned long count,
 	const char *input, int size, char *output, int output_size);
diff --git a/ext/mri/wrapper.c b/ext/mri/wrapper.c
index 1e49c90..cbba882 100644
--- a/ext/mri/wrapper.c
+++ b/ext/mri/wrapper.c
@@ -17,6 +17,9 @@
 #include <stdlib.h>
 #include <string.h>
 
+/* Redefine strdup to ruby_strdup in case string.h doesn't export it. */
+#include <ruby/util.h>
+
 #include <errno.h>
 #ifndef __set_errno
 #define __set_errno(val) errno = (val)
@@ -176,7 +179,7 @@ char *crypt_ra(const char *key, const char *setting,
 	return _crypt_blowfish_rn(key, setting, (char *)*data, *size);
 }
 
-char *crypt_r(const char *key, const char *setting, void *data)
+char *crypt_r(const char *key, const char *setting, struct crypt_data *data)
 {
 	return _crypt_retval_magic(
 		crypt_rn(key, setting, data, CRYPT_OUTPUT_SIZE),
diff --git a/ext/mri/x86.S b/ext/mri/x86.S
index b0f1cd2..4c5c069 100644
--- a/ext/mri/x86.S
+++ b/ext/mri/x86.S
@@ -199,5 +199,5 @@ BF_die:
 #endif
 
 #if defined(__ELF__) && defined(__linux__)
-.section .note.GNU-stack,"",@progbits
+.section .note.GNU-stack,"",%progbits
 #endif
diff --git a/lib/bcrypt/engine.rb b/lib/bcrypt/engine.rb
index 226d142..1a253b3 100644
--- a/lib/bcrypt/engine.rb
+++ b/lib/bcrypt/engine.rb
@@ -5,6 +5,16 @@ class Engine
     DEFAULT_COST    = 12
     # The minimum cost supported by the algorithm.
     MIN_COST        = 4
+    # The maximum cost supported by the algorithm.
+    MAX_COST = 31
+    # Maximum possible size of bcrypt() secrets.
+    # Older versions of the bcrypt library would truncate passwords longer
+    # than 72 bytes, but newer ones do not. We truncate like the old library for
+    # forward compatibility. This way users upgrading from Ubuntu 18.04 to 20.04
+    # will not have their user passwords invalidated, for example.
+    # A max secret length greater than 255 leads to bcrypt returning nil.
+    # https://github.com/bcrypt-ruby/bcrypt-ruby/issues/225#issuecomment-875908425
+    MAX_SECRET_BYTESIZE = 72
     # Maximum possible size of bcrypt() salts.
     MAX_SALT_LENGTH = 16
 
@@ -41,14 +51,23 @@ def self.cost=(cost)
     end
 
     # Given a secret and a valid salt (see BCrypt::Engine.generate_salt) calculates
-    # a bcrypt() password hash.
+    # a bcrypt() password hash. Secrets longer than 72 bytes are truncated.
     def self.hash_secret(secret, salt, _ = nil)
+      unless _.nil?
+        warn "[DEPRECATION] Passing the third argument to " \
+             "`BCrypt::Engine.hash_secret` is deprecated. " \
+             "Please do not pass the third argument which " \
+             "is currently not used."
+      end
+
       if valid_secret?(secret)
         if valid_salt?(salt)
           if RUBY_PLATFORM == "java"
             Java.bcrypt_jruby.BCrypt.hashpw(secret.to_s.to_java_bytes, salt.to_s)
           else
-            __bc_crypt(secret.to_s, salt)
+            secret = secret.to_s
+            secret = secret.byteslice(0, MAX_SECRET_BYTESIZE) if secret && secret.bytesize > MAX_SECRET_BYTESIZE
+            __bc_crypt(secret, salt)
           end
         else
           raise Errors::InvalidSalt.new("invalid salt")
@@ -68,8 +87,7 @@ def self.generate_salt(cost = self.cost)
         if RUBY_PLATFORM == "java"
           Java.bcrypt_jruby.BCrypt.gensalt(cost)
         else
-          prefix = "$2a$05$CCCCCCCCCCCCCCCCCCCCC.E5YPO9kmyuRGyh0XouQYb4YMJKvyOeW"
-          __bc_salt(prefix, cost, OpenSSL::Random.random_bytes(MAX_SALT_LENGTH))
+          __bc_salt("$2a$", cost, OpenSSL::Random.random_bytes(MAX_SALT_LENGTH))
         end
       else
         raise Errors::InvalidCost.new("cost must be numeric and > 0")
@@ -78,7 +96,7 @@ def self.generate_salt(cost = self.cost)
 
     # Returns true if +salt+ is a valid bcrypt() salt, false if not.
     def self.valid_salt?(salt)
-      !!(salt =~ /^\$[0-9a-z]{2,}\$[0-9]{2,}\$[A-Za-z0-9\.\/]{22,}$/)
+      !!(salt =~ /\A\$[0-9a-z]{2,}\$[0-9]{2,}\$[A-Za-z0-9\.\/]{22,}\z/)
     end
 
     # Returns true if +secret+ is a valid bcrypt() secret, false if not.
@@ -99,7 +117,7 @@ def self.valid_secret?(secret)
     #   # should take less than 1000ms
     #   BCrypt::Password.create("woo", :cost => 12)
     def self.calibrate(upper_time_limit_in_ms)
-      40.times do |i|
+      (BCrypt::Engine::MIN_COST..BCrypt::Engine::MAX_COST-1).each do |i|
         start_time = Time.now
         Password.create("testing testing", :cost => i+1)
         end_time = Time.now - start_time
diff --git a/lib/bcrypt/password.rb b/lib/bcrypt/password.rb
index 509a8d9..0c432d6 100644
--- a/lib/bcrypt/password.rb
+++ b/lib/bcrypt/password.rb
@@ -42,12 +42,12 @@ class << self
       #   @password = BCrypt::Password.create("my secret", :cost => 13)
       def create(secret, options = {})
         cost = options[:cost] || BCrypt::Engine.cost
-        raise ArgumentError if cost > 31
+        raise ArgumentError if cost > BCrypt::Engine::MAX_COST
         Password.new(BCrypt::Engine.hash_secret(secret, BCrypt::Engine.generate_salt(cost)))
       end
 
       def valid_hash?(h)
-        h =~ /^\$[0-9a-z]{2}\$[0-9]{2}\$[A-Za-z0-9\.\/]{53}$/
+        /\A\$[0-9a-z]{2}\$[0-9]{2}\$[A-Za-z0-9\.\/]{53}\z/ === h
       end
     end
 
@@ -62,8 +62,28 @@ def initialize(raw_hash)
     end
 
     # Compares a potential secret against the hash. Returns true if the secret is the original secret, false otherwise.
+    #
+    # Comparison edge case/gotcha:
+    #
+    #    secret = "my secret"
+    #    @password = BCrypt::Password.create(secret)
+    #
+    #    @password == secret              # => True
+    #    @password == @password           # => False
+    #    @password == @password.to_s      # => False
+    #    @password.to_s == @password      # => True
+    #    @password.to_s == @password.to_s # => True
+    #
+    #    secret == @password              # => probably False, because the secret is not a BCrypt::Password instance.
     def ==(secret)
-      super(BCrypt::Engine.hash_secret(secret, @salt))
+      hash = BCrypt::Engine.hash_secret(secret, @salt)
+
+      return false if hash.strip.empty? || strip.empty? || hash.bytesize != bytesize
+
+      # Constant time comparison so they can't tell the length.
+      res = 0
+      bytesize.times { |i| res |= getbyte(i) ^ hash.getbyte(i) }
+      res == 0
     end
     alias_method :is_password?, :==
 
@@ -83,5 +103,4 @@ def split_hash(h)
       return v.to_str, c.to_i, h[0, 29].to_str, mash[-31, 31].to_str
     end
   end
-
 end
diff --git a/spec/bcrypt/engine_spec.rb b/spec/bcrypt/engine_spec.rb
index cde842c..8abbe9f 100644
--- a/spec/bcrypt/engine_spec.rb
+++ b/spec/bcrypt/engine_spec.rb
@@ -1,9 +1,23 @@
 require File.expand_path(File.join(File.dirname(__FILE__), "..", "spec_helper"))
+require 'securerandom'
+
+describe 'BCrypt::Engine' do
+  describe '.calibrate(upper_time_limit_in_ms)' do
+    context 'a tiny upper time limit provided' do
+      it 'returns a minimum cost supported by the algorithm' do
+        expect(BCrypt::Engine.calibrate(0.001)).to eq(4)
+      end
+    end
+  end
+end
 
 describe "The BCrypt engine" do
   specify "should calculate the optimal cost factor to fit in a specific time" do
-    first = BCrypt::Engine.calibrate(100)
-    second = BCrypt::Engine.calibrate(400)
+    start_time = Time.now
+    BCrypt::Password.create("testing testing", :cost => BCrypt::Engine::MIN_COST + 1)
+    min_time_ms = (Time.now - start_time) * 1000
+    first = BCrypt::Engine.calibrate(min_time_ms)
+    second = BCrypt::Engine.calibrate(min_time_ms * 5)
     expect(second).to be > first
   end
 end
@@ -144,4 +158,19 @@ class MyInvalidSecret
       expect(BCrypt::Engine.hash_secret(secret, salt)).to eql(test_vector)
     end
   end
+
+  specify "should truncate long 1-byte character secrets to 72 bytes" do
+    # 'b' as a base triggers the failure at 256 characters, but 'a' does not.
+    too_long_secret = 'b'*(BCrypt::Engine::MAX_SECRET_BYTESIZE + 1)
+    just_right_secret = 'b'*BCrypt::Engine::MAX_SECRET_BYTESIZE
+    expect(BCrypt::Engine.hash_secret(too_long_secret, @salt)).to eq(BCrypt::Engine.hash_secret(just_right_secret, @salt))
+  end
+
+  specify "should truncate long multi-byte character secrets to 72 bytes" do
+    # 256 times causes bcrypt to return nil for libxcrypt > 4.4.18-4.
+    too_long_secret = '𐐷'*256
+    # 𐐷 takes 4 bytes in UTF-8. 18 times is 72 bytes
+    just_right_secret = '𐐷'*18
+    expect(BCrypt::Engine.hash_secret(too_long_secret, @salt)).to eq(BCrypt::Engine.hash_secret(just_right_secret, @salt))
+  end
 end
diff --git a/spec/bcrypt/password_spec.rb b/spec/bcrypt/password_spec.rb
index 648e614..5a93cbd 100644
--- a/spec/bcrypt/password_spec.rb
+++ b/spec/bcrypt/password_spec.rb
@@ -1,4 +1,5 @@
 require File.expand_path(File.join(File.dirname(__FILE__), "..", "spec_helper"))
+require 'securerandom'
 
 describe "Creating a hashed password" do
 
@@ -26,6 +27,16 @@
     expect { BCrypt::Password.create( ""         ) }.not_to raise_error
     expect { BCrypt::Password.create( String.new ) }.not_to raise_error
   end
+
+  specify "should tolerate very long string secrets" do
+    expect { BCrypt::Password.create("abcd"*1024) }.not_to raise_error
+  end
+
+  specify "blows up when null bytes are in the string" do
+    # JRuby can handle the null bytes
+    skip if RUBY_ENGINE == 'jruby'
+    expect { BCrypt::Password.create( "foo\0bar".chop  ) }.to raise_error
+  end
 end
 
 describe "Reading a hashed password" do
@@ -108,6 +119,7 @@
 describe "Validating a generated salt" do
   specify "should not accept an invalid salt" do
     expect(BCrypt::Engine.valid_salt?("invalid")).to eq(false)
+    expect(BCrypt::Engine.valid_salt?("invalid\n#{BCrypt::Engine.generate_salt}\ninvalid")).to eq(false)
   end
   specify "should accept a valid salt" do
     expect(BCrypt::Engine.valid_salt?(BCrypt::Engine.generate_salt)).to eq(true)
@@ -116,9 +128,10 @@
 
 describe "Validating a password hash" do
   specify "should not accept an invalid password" do
-    expect(BCrypt::Password.valid_hash?("i_am_so_not_valid")).to be_falsey
+    expect(BCrypt::Password.valid_hash?("i_am_so_not_valid")).to be(false)
+    expect(BCrypt::Password.valid_hash?("invalid\n#{BCrypt::Password.create "i_am_so_valid"}\ninvalid")).to be(false)
   end
   specify "should accept a valid password" do
-    expect(BCrypt::Password.valid_hash?(BCrypt::Password.create "i_am_so_valid")).to be_truthy
+    expect(BCrypt::Password.valid_hash?(BCrypt::Password.create "i_am_so_valid")).to be(true)
   end
 end