diff --git a/lib/devise/encryptable/encryptable.rb b/lib/devise/encryptable/encryptable.rb
index 441ed4e..65dd8c4 100644
--- a/lib/devise/encryptable/encryptable.rb
+++ b/lib/devise/encryptable/encryptable.rb
@@ -19,6 +19,8 @@ module Devise
 
   module Encryptable
     module Encryptors
+      InvalidHash = Class.new(StandardError)
+
       autoload :AuthlogicSha512, 'devise/encryptable/encryptors/authlogic_sha512'
       autoload :Base, 'devise/encryptable/encryptors/base'
       autoload :ClearanceSha1, 'devise/encryptable/encryptors/clearance_sha1'
diff --git a/lib/devise/encryptable/encryptors/pbkdf2.rb b/lib/devise/encryptable/encryptors/pbkdf2.rb
index cf0a3d8..bbdf75e 100644
--- a/lib/devise/encryptable/encryptors/pbkdf2.rb
+++ b/lib/devise/encryptable/encryptors/pbkdf2.rb
@@ -1,23 +1,66 @@
-begin
-  module Devise
-    module Encryptable
-      module Encryptors
-        class Pbkdf2 < Base
-          def self.compare(encrypted_password, password, stretches, salt, pepper)
-            value_to_test = self.digest(password, stretches, salt, pepper)
-            Devise.secure_compare(encrypted_password, value_to_test)
-          end
-
-          def self.digest(password, stretches, salt, pepper)
-            hash = OpenSSL::Digest.new('SHA512').new
-            OpenSSL::KDF.pbkdf2_hmac(
-              password.to_s,
-              salt: "#{[salt].pack('H*')}#{pepper}",
-              iterations: stretches,
-              hash: hash,
-              length: hash.digest_length,
-            ).unpack1('H*')
-          end
+module Devise
+  module Encryptable
+    module Encryptors
+      # https://en.wikipedia.org/wiki/PBKDF2
+      # Adapted from https://gitlab.com/gitlab-org/gitlab/-/blob/373f088e755f678478b8dd1627fab908d2641b21/vendor/gems/devise-pbkdf2-encryptable/lib/devise/pbkdf2_encryptable/encryptors/pbkdf2_sha512.rb
+      class Pbkdf2 < Base
+        STRATEGY = 'pbkdf2-sha512'
+
+        # since stretches and iterations are part of the hashed pass, so ignore them during comparing
+        def self.compare(encrypted_password, password, _stretches, _salt, pepper)
+          split_digest = self.split_digest(encrypted_password)
+          value_to_test = sha512_checksum(password, split_digest[:stretches], split_digest[:salt], pepper)
+
+          Devise.secure_compare(split_digest[:checksum], value_to_test)
+        end
+
+        def self.digest(password, stretches, salt, pepper)
+          checksum = sha512_checksum(password, stretches, salt, pepper)
+
+          format_hash(STRATEGY, stretches, salt, checksum)
+        end
+
+        private_class_method def self.sha512_checksum(password, stretches, salt, pepper)
+          hash = OpenSSL::Digest.new('SHA512')
+          pbkdf2_checksum(hash, password, stretches, salt, pepper)
+        end
+
+        private_class_method def self.pbkdf2_checksum(hash, password, stretches, salt, pepper)
+          OpenSSL::KDF.pbkdf2_hmac(
+            password.to_s,
+            salt: "#{[salt].pack('H*')}#{pepper}",
+            iterations: stretches,
+            hash: hash,
+            length: hash.digest_length
+          ).unpack1('H*')
+        end
+
+        # Passlib-style hash: $pbkdf2-sha512$rounds$salt$checksum
+        # where salt and checksum are "adapted" Base64 encoded
+        private_class_method def self.format_hash(strategy, stretches, salt, checksum)
+          encoded_salt = passlib_encode64(salt)
+          encoded_checksum = passlib_encode64(checksum)
+
+          "$#{strategy}$#{stretches}$#{encoded_salt}$#{encoded_checksum}"
+        end
+
+        private_class_method def self.passlib_encode64(value)
+          Base64.strict_encode64([value].pack('H*')).tr('+', '.').delete('=')
+        end
+
+        private_class_method def self.passlib_decode64(value)
+          enc = value.tr('.', '+')
+          Base64.decode64(enc).unpack1('H*')
+        end
+
+        private_class_method def self.split_digest(hash)
+          split_digest = hash.split('$')
+          _, strategy, stretches, salt, checksum = split_digest
+
+          raise InvalidHash, 'invalid PBKDF2 hash' unless split_digest.length == 5 && strategy.start_with?('pbkdf2-')
+
+          { strategy: strategy, stretches: stretches.to_i,
+            salt: passlib_decode64(salt), checksum: passlib_decode64(checksum) }
         end
       end
     end
diff --git a/test/devise/encryptable/encryptors/pbkdf2_test.rb b/test/devise/encryptable/encryptors/pbkdf2_test.rb
new file mode 100644
index 0000000..21c5146
--- /dev/null
+++ b/test/devise/encryptable/encryptors/pbkdf2_test.rb
@@ -0,0 +1,61 @@
+require 'test_helper'
+require 'benchmark'
+
+class PBKDF2Test < ActiveSupport::TestCase
+  include Support::Assertions
+  include Support::Factories
+  include Support::Swappers
+
+  STETCHES = 210_000
+  PEPPER = 'thisisasuperlongstringusedontopofsalt'.freeze
+
+  def encrypt_password(admin, pepper = Admin.pepper, stretches = Admin.stretches, encryptor = Admin.encryptor_class)
+    encryptor.digest('123456', stretches, admin.password_salt, pepper)
+  end
+
+  def random_salt
+    Devise::Encryptable::Encryptors::Base.salt(STETCHES)
+  end
+
+  test 'digest and compare success' do
+    plain_pass = 'password1'
+    hashed_password = Devise::Encryptable::Encryptors::Pbkdf2.digest(plain_pass, STETCHES, random_salt, PEPPER)
+    assert Devise::Encryptable::Encryptors::Pbkdf2.compare(hashed_password, plain_pass, nil, nil, PEPPER)
+  end
+
+  test 'invalid password hash raise' do
+    plain_pass = 'password1'
+    assert_raise(Devise::Encryptable::Encryptors::InvalidHash) do
+      Devise::Encryptable::Encryptors::Pbkdf2.compare('wrongformatpasshash', plain_pass, nil, nil, PEPPER)
+    end
+  end
+
+  test 'wrong password' do
+    plain_pass = 'password1'
+    hashed_password = Devise::Encryptable::Encryptors::Pbkdf2.digest(plain_pass, 210_000, random_salt, PEPPER)
+    assert !Devise::Encryptable::Encryptors::Pbkdf2.compare(hashed_password, 'wrongpass', nil, nil, PEPPER)
+  end
+
+  test 'changed pepper will fail password check' do
+    plain_pass = 'password1'
+    hashed_password = Devise::Encryptable::Encryptors::Pbkdf2.digest(plain_pass, 210_000, random_salt, PEPPER)
+    assert !Devise::Encryptable::Encryptors::Pbkdf2.compare(hashed_password, plain_pass, nil, nil,
+                                                            'opps, different pepper')
+  end
+
+  test 'devise using Pbkdf2' do
+    swap_with_encryptor Admin, :Pbkdf2 do
+      admin = create_admin
+      assert_equal admin.encrypted_password,
+                   encrypt_password(admin, Admin.pepper, Admin.stretches, Devise::Encryptable::Encryptors::Pbkdf2)
+    end
+  end
+
+  test 'devise can compare using Pbkdf2' do
+    swap_with_encryptor Admin, :Pbkdf2 do
+      plain_pass = 'password1'
+      admin = create_admin(password: plain_pass)
+      assert admin.valid_password?(plain_pass)
+    end
+  end
+end