diff --git a/core/core.services.yml b/core/core.services.yml
index 5c42b23..2ff42ef 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -41,6 +41,7 @@ parameters:
     exposedHeaders: false
     maxAge: false
     supportsCredentials: false
+  password_hash_cost: 10
 services:
   # Simple cache contexts, directly derived from the request context.
   cache_context.ip:
@@ -914,14 +915,17 @@ services:
     class: Drupal\Core\Path\PathValidator
     arguments: ['@router', '@router.no_access_checks', '@current_user', '@path_processor_manager']
 
-# The argument to the hashing service defined in services.yml, to the
-# constructor of PhpassHashedPassword is the log2 number of iterations for
-# password stretching.
-# @todo increase by 1 every Drupal version in order to counteract increases in
-# the speed and power of computers available to crack the hashes. The current
-# password hashing method was introduced in Drupal 7 with a log2 count of 15.
+# The first argument of the hashing service (constructor of PhpPassword) is
+# the 'cost' option of password_hash(). In Drupal 8 the 'cost' has the default
+# value used by password_hash() which is 10. Future versions of Drupal may
+# increase this value in order to counteract increases in the speed and power
+# of computers available to crack the hashes. Note that an increase of 1 will
+# double the time needed for password hashing.
   password:
-    class: Drupal\Core\Password\PhpassHashedPassword
+    class: Drupal\Core\Password\PhpPassword
+    arguments: ['%password_hash_cost%', '@drupal7_password']
+  drupal7_password:
+    class: Drupal\Core\Password\Drupal7Password
     arguments: [16]
   request_format_route_filter:
     class: Drupal\Core\Routing\RequestFormatRouteFilter
diff --git a/core/lib/Drupal/Core/Password/PhpassHashedPassword.php b/core/lib/Drupal/Core/Password/Drupal7Password.php
similarity index 95%
rename from core/lib/Drupal/Core/Password/PhpassHashedPassword.php
rename to core/lib/Drupal/Core/Password/Drupal7Password.php
index 28313d2..4a39f68 100644
--- a/core/lib/Drupal/Core/Password/PhpassHashedPassword.php
+++ b/core/lib/Drupal/Core/Password/Drupal7Password.php
@@ -8,9 +8,13 @@
  * Secure password hashing functions based on the Portable PHP password
  * hashing framework.
  *
+ * This is a custom password hashing mechanism used in Drupal 7. We keep this
+ * password hasher in order to validate passwords migrated from Drupal 7 that
+ * are being rehashed on first user login.
+ *
  * @see http://www.openwall.com/phpass/
  */
-class PhpassHashedPassword implements PasswordInterface {
+class Drupal7Password implements PasswordInterface {
   /**
    * The minimum allowed log2 number of iterations for password stretching.
    */
@@ -218,7 +222,7 @@ public function hash($password) {
   /**
    * {@inheritdoc}
    */
-  public function check($password, $hash) {
+  public function verify($password, $hash) {
     if (substr($hash, 0, 2) == 'U$') {
       // This may be an updated password from user_update_7000(). Such hashes
       // have 'U' added as the first character and need an extra md5() (see the
@@ -247,8 +251,7 @@ public function check($password, $hash) {
         return FALSE;
     }
 
-    // Compare using hashEquals() instead of === to mitigate timing attacks.
-    return $computed_hash && Crypt::hashEquals($stored_hash, $computed_hash);
+    return ($computed_hash && $stored_hash === $computed_hash);
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Password/PasswordInterface.php b/core/lib/Drupal/Core/Password/PasswordInterface.php
index b38cc79..c2d14e9 100644
--- a/core/lib/Drupal/Core/Password/PasswordInterface.php
+++ b/core/lib/Drupal/Core/Password/PasswordInterface.php
@@ -34,7 +34,7 @@ public function hash($password);
    * @return bool
    *   TRUE if the password is valid, FALSE if not.
    */
-  public function check($password, $hash);
+  public function verify($password, $hash);
 
   /**
    * Check whether a hashed password needs to be replaced with a new hash.
diff --git a/core/lib/Drupal/Core/Password/PhpPassword.php b/core/lib/Drupal/Core/Password/PhpPassword.php
new file mode 100644
index 0000000..fa2ef02
--- /dev/null
+++ b/core/lib/Drupal/Core/Password/PhpPassword.php
@@ -0,0 +1,97 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Password\PhpPassword.
+ */
+
+namespace Drupal\Core\Password;
+
+/**
+ * Secure password hashing functions based on PHP (>=5.5.0) password hashing
+ * functions.
+ *
+ * @see http://php.net/manual/en/book.password.php
+ */
+class PhpPassword implements PasswordInterface {
+
+  /**
+   * The algorithmic cost that should be used. This is the same 'cost' option as
+   * is used by the PHP (>= 5.5.0) password_hash() function.
+   *
+   * @var int
+   *
+   * @see password_hash().
+   * @see http://php.net/manual/en/ref.password.php
+   */
+  protected $cost;
+
+  /**
+   * The Drupal 7 password hashing service.
+   *
+   * @var \Drupal\Core\Password\Drupal7Password
+   */
+  protected $drupal7Password;
+
+  /**
+   * Constructs a new password hashing instance.
+   *
+   * @param int $cost
+   *   The algorithmic cost that should be used.
+   * @param \Drupal\Core\Password\PasswordInterface $drupal7_password
+   *   The Drupal7 password hashing service.
+   */
+  function __construct($cost, PasswordInterface $drupal7_password) {
+    $this->cost = $cost;
+    $this->drupal7Password = $drupal7_password;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function hash($password) {
+    // Prevent DoS attacks by refusing to hash large passwords.
+    if (strlen($password) > static::PASSWORD_MAX_LENGTH) {
+      return FALSE;
+    }
+
+    return password_hash($password, PASSWORD_BCRYPT, $this->getOptions());
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function verify($password, $hash) {
+    // Try to verify an legacy hash. This may be an Drupal 6 or 7 hash.
+    if (substr($hash, 0, 4) != '$2y$') {
+      return $this->drupal7Password->verify($password, $hash);
+    }
+
+    return password_verify($password, $hash);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function needsRehash($hash) {
+    // The PHP 5.5 password_needs_rehash() will return TRUE in two cases:
+    // - The password is either a Drupal 6 MD5 hash rehashed during migration,
+    //   either a Drupal 7 hashed password. In this case the legacy hash will
+    //   not comply the expected password_needs_rehash() format (prefix '$2y$').
+    // - The parameters of hashing engine were changed. For example the
+    //   parameter 'password_hash_cost' (the hashing cost) has been increased in
+    //   core.services.yml.
+    return password_needs_rehash($hash, PASSWORD_BCRYPT, $this->getOptions());
+  }
+
+  /**
+   * Returns password options.
+   *
+   * @return array
+   *   Associative array with password options.
+   */
+  protected function getOptions() {
+    return ['cost' => $this->cost];
+  }
+
+}
diff --git a/core/modules/migrate_drupal/tests/fixtures/drupal7.php b/core/modules/migrate_drupal/tests/fixtures/drupal7.php
index 98e5638..e2928a3 100644
--- a/core/modules/migrate_drupal/tests/fixtures/drupal7.php
+++ b/core/modules/migrate_drupal/tests/fixtures/drupal7.php
@@ -34021,7 +34021,7 @@
   'weight' => '0',
 ))
 ->values(array(
-  'name' => 'PasswordHashingTest',
+  'name' => 'Drupal7PasswordTest',
   'type' => 'class',
   'filename' => 'modules/simpletest/tests/password.test',
   'module' => 'simpletest',
diff --git a/core/modules/simpletest/src/KernelTestBase.php b/core/modules/simpletest/src/KernelTestBase.php
index fbf58a5..cd39245 100644
--- a/core/modules/simpletest/src/KernelTestBase.php
+++ b/core/modules/simpletest/src/KernelTestBase.php
@@ -364,8 +364,9 @@ public function containerBuild(ContainerBuilder $container) {
       $definition->clearTag('path_processor_inbound')->clearTag('path_processor_outbound');
     }
 
-    if ($container->hasDefinition('password')) {
-      $container->getDefinition('password')->setArguments(array(1));
+    if ($container->hasDefinition('password') && $container->hasDefinition('drupal7_password')) {
+      $container->getDefinition('drupal7_password')->setArguments([1]);
+      $container->getDefinition('password')->setArguments([4, $container->get('drupal7_password')]);
     }
 
     // Register the stream wrapper manager.
diff --git a/core/modules/user/src/Entity/User.php b/core/modules/user/src/Entity/User.php
index 062af44..3d6fbd2 100644
--- a/core/modules/user/src/Entity/User.php
+++ b/core/modules/user/src/Entity/User.php
@@ -395,7 +395,7 @@ public function setExistingPassword($password) {
    * {@inheritdoc}
    */
   public function checkExistingPassword(UserInterface $account_unchanged) {
-    return strlen($this->get('pass')->existing) > 0 && \Drupal::service('password')->check(trim($this->get('pass')->existing), $account_unchanged->getPassword());
+    return strlen($this->get('pass')->existing) > 0 && \Drupal::service('password')->verify(trim($this->get('pass')->existing), $account_unchanged->getPassword());
   }
 
   /**
diff --git a/core/modules/user/src/Tests/UserLoginTest.php b/core/modules/user/src/Tests/UserLoginTest.php
index af00c74..19353b4 100644
--- a/core/modules/user/src/Tests/UserLoginTest.php
+++ b/core/modules/user/src/Tests/UserLoginTest.php
@@ -4,6 +4,7 @@
 
 use Drupal\simpletest\WebTestBase;
 use Drupal\user\Entity\User;
+use Drupal\user\UserInterface;
 
 /**
  * Ensure that login works as expected.
@@ -13,6 +14,20 @@
 class UserLoginTest extends WebTestBase {
 
   /**
+   * Drupal password hasher service.
+   *
+   * @var \Drupal\Core\Password\PasswordInterface
+   */
+  private $passwordHasher;
+
+  /**
+   * Drupal 7 password hasher service.
+   *
+   * @var \Drupal\Core\Password\PasswordInterface
+   */
+   private $drupal7PasswordHasher;
+
+  /**
    * Tests login with destination.
    */
   function testLoginCacheTagsAndDestination() {
@@ -26,6 +41,9 @@ function testLoginCacheTagsAndDestination() {
     $edit = array('name' => $user->getUserName(), 'pass' => $user->pass_raw);
     $this->drupalPostForm(NULL, $edit, t('Log in'));
     $this->assertUrl('foo', [], 'Redirected to the correct URL');
+
+    $this->passwordHasher = $this->container->get('password');
+    $this->drupal7PasswordHasher = $this->container->get('drupal7_password');
   }
 
   /**
@@ -106,30 +124,23 @@ function testPerUserLoginFloodControl() {
   }
 
   /**
-   * Test that user password is re-hashed upon login after changing $count_log2.
+   * Test that user password is re-hashed upon login after changing the cost.
    */
   function testPasswordRehashOnLogin() {
-    // Determine default log2 for phpass hashing algorithm
-    $default_count_log2 = 16;
-
-    // Retrieve instance of password hashing algorithm
-    $password_hasher = $this->container->get('password');
-
     // Create a new user and authenticate.
     $account = $this->drupalCreateUser(array());
     $password = $account->pass_raw;
     $this->drupalLogin($account);
     $this->drupalLogout();
-    // Load the stored user. The password hash should reflect $default_count_log2.
+    // Load the stored user. The password hash should reflect $default_cost.
     $user_storage = $this->container->get('entity.manager')->getStorage('user');
     $account = User::load($account->id());
-    $this->assertIdentical($password_hasher->getCountLog2($account->getPassword()), $default_count_log2);
+    $this->assertTrue($this->passwordHasher->verify($password, $account->getPassword()));
 
-    // Change the required number of iterations by loading a test-module
-    // containing the necessary container builder code and then verify that the
-    // users password gets rehashed during the login.
-    $overridden_count_log2 = 19;
-    \Drupal::service('module_installer')->install(array('user_custom_phpass_params_test'));
+    // Change the required cost by loading a test-module containing the
+    // necessary container builder code and then verify that the users password
+    // gets rehashed during the login.
+    \Drupal::service('module_installer')->install(array('user_custom_pass_hash_params_test'));
     $this->resetAll();
 
     $account->pass_raw = $password;
@@ -137,11 +148,51 @@ function testPasswordRehashOnLogin() {
     // Load the stored user, which should have a different password hash now.
     $user_storage->resetCache(array($account->id()));
     $account = $user_storage->load($account->id());
-    $this->assertIdentical($password_hasher->getCountLog2($account->getPassword()), $overridden_count_log2);
-    $this->assertTrue($password_hasher->check($password, $account->getPassword()));
+    $this->assertTrue($this->passwordHasher->verify($password, $account->getPassword()));
   }
 
   /**
+   * Test MD5 (Drupal 6) passwords rehashing.
+   */
+  public function testDrupal6MigratedPasswordRehashing() {
+    /** @var \Drupal\user\UserInterface $account */
+    $account = $this->drupalCreateUser();
+    $plain = $account->pass_raw;
+
+    // We pretend that the user was migrated from Drupal 6.
+    $md5_pass = md5($plain);
+    $migrated_pass = 'U' . $this->passwordHasher->hash($md5_pass);
+    $this->storeHashedPassword($account, $migrated_pass);
+
+    // User first login after migration.
+    $this->drupalLogin($account);
+    $this->drupalLogout();
+
+    // After logging in the user password has been rehashed and is valid.
+    $this->assertTrue($this->passwordHasher->verify($plain, $account->getPassword()));
+}
+
+  /**
+   * Test Drupal 7 passwords rehashing.
+   */
+  public function testDrupal7MigratedPasswordRehashing() {
+  /** @var \Drupal\user\UserInterface $account */
+  $account = $this->drupalCreateUser();
+  $plain = $account->pass_raw;
+
+  // We pretend that the user was migrated from Drupal 7.
+  $d7_hash = $this->drupal7PasswordHasher->hash($plain);
+  $this->storeHashedPassword($account, $d7_hash);
+
+  // User first login after migration.
+  $this->drupalLogin($account);
+  $this->drupalLogout();
+
+  // After logging in the user password has been rehashed and is valid.
+  $this->assertTrue($this->passwordHasher->verify($plain, $account->getPassword()));
+}
+
+  /**
    * Make an unsuccessful login attempt.
    *
    * @param \Drupal\user\Entity\User $account
@@ -175,4 +226,22 @@ function assertFailedLogin($account, $flood_trigger = NULL) {
     }
   }
 
+  /**
+   * Updates the hashed user password bypassing the API.
+   *
+   * We want to set an already hashed password.
+   *
+   * @param \Drupal\user\UserInterface $account
+   *   The user account.
+   * @param string $hashed_password
+   *   An already hashed password.
+   */
+  protected function storeHashedPassword(UserInterface $account, $hashed_password) {
+    $account->setPassword($hashed_password);
+    db_update('users_field_data')
+      ->fields(['pass' => $hashed_password])
+      ->condition('uid', $account->id())
+      ->execute();
+  }
+
 }
diff --git a/core/modules/user/src/UserAuth.php b/core/modules/user/src/UserAuth.php
index 9fbcf09..30da858 100644
--- a/core/modules/user/src/UserAuth.php
+++ b/core/modules/user/src/UserAuth.php
@@ -47,7 +47,7 @@ public function authenticate($username, $password) {
       $account_search = $this->entityManager->getStorage('user')->loadByProperties(array('name' => $username));
 
       if ($account = reset($account_search)) {
-        if ($this->passwordChecker->check($password, $account->getPassword())) {
+        if ($this->passwordChecker->verify($password, $account->getPassword())) {
           // Successful authentication.
           $uid = $account->id();
 
diff --git a/core/modules/user/tests/modules/user_custom_pass_hash_params_test/user_custom_pass_hash_params_test.info.yml b/core/modules/user/tests/modules/user_custom_pass_hash_params_test/user_custom_pass_hash_params_test.info.yml
new file mode 100644
index 0000000..aca50c4
--- /dev/null
+++ b/core/modules/user/tests/modules/user_custom_pass_hash_params_test/user_custom_pass_hash_params_test.info.yml
@@ -0,0 +1,6 @@
+name: 'User custom password hash params test'
+type: module
+description: 'Support module for testing custom hashing password algorithm parameters.'
+package: Testing
+version: VERSION
+core: 8.x
diff --git a/core/modules/user/tests/modules/user_custom_pass_hash_params_test/user_custom_pass_hash_params_test.services.yml b/core/modules/user/tests/modules/user_custom_pass_hash_params_test/user_custom_pass_hash_params_test.services.yml
new file mode 100644
index 0000000..56c1281
--- /dev/null
+++ b/core/modules/user/tests/modules/user_custom_pass_hash_params_test/user_custom_pass_hash_params_test.services.yml
@@ -0,0 +1,7 @@
+services:
+  password:
+    class: Drupal\Core\Password\PhpPassword
+    arguments: [11, '@drupal7_password']
+  drupal7_password:
+    class: Drupal\Core\Password\Drupal7Password
+    arguments: [16]
diff --git a/core/modules/user/tests/modules/user_custom_phpass_params_test/user_custom_phpass_params_test.info.yml b/core/modules/user/tests/modules/user_custom_phpass_params_test/user_custom_phpass_params_test.info.yml
deleted file mode 100644
index 68b8ff9..0000000
--- a/core/modules/user/tests/modules/user_custom_phpass_params_test/user_custom_phpass_params_test.info.yml
+++ /dev/null
@@ -1,6 +0,0 @@
-name: 'User custom phpass params test'
-type: module
-description: 'Support module for testing custom phpass password algorithm parameters.'
-package: Testing
-version: VERSION
-core: 8.x
diff --git a/core/modules/user/tests/modules/user_custom_phpass_params_test/user_custom_phpass_params_test.services.yml b/core/modules/user/tests/modules/user_custom_phpass_params_test/user_custom_phpass_params_test.services.yml
deleted file mode 100644
index 8950bfe..0000000
--- a/core/modules/user/tests/modules/user_custom_phpass_params_test/user_custom_phpass_params_test.services.yml
+++ /dev/null
@@ -1,4 +0,0 @@
-services:
-  password:
-    class: Drupal\Core\Password\PhpassHashedPassword
-    arguments: [19]
diff --git a/core/modules/user/tests/src/Unit/UserAuthTest.php b/core/modules/user/tests/src/Unit/UserAuthTest.php
index 1b96d8f..6d28101 100644
--- a/core/modules/user/tests/src/Unit/UserAuthTest.php
+++ b/core/modules/user/tests/src/Unit/UserAuthTest.php
@@ -129,7 +129,7 @@ public function testAuthenticateWithIncorrectPassword() {
       ->will($this->returnValue(array($this->testUser)));
 
     $this->passwordService->expects($this->once())
-      ->method('check')
+      ->method('verify')
       ->with($this->password, $this->testUser->getPassword())
       ->will($this->returnValue(FALSE));
 
@@ -152,7 +152,7 @@ public function testAuthenticateWithCorrectPassword() {
       ->will($this->returnValue(array($this->testUser)));
 
     $this->passwordService->expects($this->once())
-      ->method('check')
+      ->method('verify')
       ->with($this->password, $this->testUser->getPassword())
       ->will($this->returnValue(TRUE));
 
@@ -179,7 +179,7 @@ public function testAuthenticateWithZeroPassword() {
       ->will($this->returnValue(array($this->testUser)));
 
     $this->passwordService->expects($this->once())
-      ->method('check')
+      ->method('verify')
       ->with(0, 0)
       ->will($this->returnValue(TRUE));
 
@@ -207,7 +207,7 @@ public function testAuthenticateWithCorrectPasswordAndNewPasswordHash() {
       ->will($this->returnValue(array($this->testUser)));
 
     $this->passwordService->expects($this->once())
-      ->method('check')
+      ->method('verify')
       ->with($this->password, $this->testUser->getPassword())
       ->will($this->returnValue(TRUE));
     $this->passwordService->expects($this->once())
diff --git a/core/tests/Drupal/KernelTests/KernelTestBase.php b/core/tests/Drupal/KernelTests/KernelTestBase.php
index 4da96ba..3b72863 100644
--- a/core/tests/Drupal/KernelTests/KernelTestBase.php
+++ b/core/tests/Drupal/KernelTests/KernelTestBase.php
@@ -624,9 +624,11 @@ public function register(ContainerBuilder $container) {
         ->clearTag('path_processor_outbound');
     }
 
-    if ($container->hasDefinition('password')) {
+    if ($container->hasDefinition('password') && $container->hasDefinition('drupal7_password')) {
+      $container->getDefinition('drupal7_password')
+        ->setArguments([1]);
       $container->getDefinition('password')
-        ->setArguments(array(1));
+        ->setArguments([4, $container->get('drupal7_password')]);
     }
     TestServiceProvider::addRouteProvider($container);
   }
diff --git a/core/tests/Drupal/Tests/Core/Password/PasswordHashingTest.php b/core/tests/Drupal/Tests/Core/Password/Drupal7PasswordTest.php
similarity index 73%
rename from core/tests/Drupal/Tests/Core/Password/PasswordHashingTest.php
rename to core/tests/Drupal/Tests/Core/Password/Drupal7PasswordTest.php
index 5c378ed..70795f8 100644
--- a/core/tests/Drupal/Tests/Core/Password/PasswordHashingTest.php
+++ b/core/tests/Drupal/Tests/Core/Password/Drupal7PasswordTest.php
@@ -2,22 +2,22 @@
 
 /**
  * @file
- * Contains \Drupal\Tests\Core\Password\PasswordHashingTest.
+ * Contains Drupal\system\Tests\System\Drupal7PasswordTest.
  */
 
 namespace Drupal\Tests\Core\Password;
 
-use Drupal\Core\Password\PhpassHashedPassword;
+use Drupal\Core\Password\Drupal7Password;
 use Drupal\Core\Password\PasswordInterface;
 use Drupal\Tests\UnitTestCase;
 
 /**
  * Unit tests for password hashing API.
  *
- * @coversDefaultClass \Drupal\Core\Password\PhpassHashedPassword
+ * @coversDefaultClass \Drupal\Core\Password\Drupal7Password
  * @group System
  */
-class PasswordHashingTest extends UnitTestCase {
+class Drupal7PasswordTest extends UnitTestCase {
 
   /**
    * The user for testing.
@@ -50,7 +50,7 @@ class PasswordHashingTest extends UnitTestCase {
   /**
    * The password hasher under test.
    *
-   * @var \Drupal\Core\Password\PhpassHashedPassword
+   * @var \Drupal\Core\Password\Drupal7Password
    */
   protected $passwordHasher;
 
@@ -60,7 +60,7 @@ class PasswordHashingTest extends UnitTestCase {
   protected function setUp() {
     parent::setUp();
     $this->password = $this->randomMachineName();
-    $this->passwordHasher = new PhpassHashedPassword(1);
+    $this->passwordHasher = new Drupal7Password(1);
     $this->hashedPassword = $this->passwordHasher->hash($this->password);
     $this->md5HashedPassword = 'U' . $this->passwordHasher->hash(md5($this->password));
   }
@@ -71,12 +71,11 @@ protected function setUp() {
    * @covers ::enforceLog2Boundaries
    */
   public function testWithinBounds() {
-    $hasher = new FakePhpassHashedPassword();
-    $this->assertEquals(PhpassHashedPassword::MIN_HASH_COUNT, $hasher->enforceLog2Boundaries(1), "Min hash count enforced");
-    $this->assertEquals(PhpassHashedPassword::MAX_HASH_COUNT, $hasher->enforceLog2Boundaries(100), "Max hash count enforced");
+    $hasher = new FakeDrupal7Password();
+    $this->assertEquals(Drupal7Password::MIN_HASH_COUNT, $hasher->enforceLog2Boundaries(1), 'Min hash count enforced');
+    $this->assertEquals(Drupal7Password::MAX_HASH_COUNT, $hasher->enforceLog2Boundaries(100), 'Max hash count enforced');
   }
 
-
   /**
    * Test a password needs update.
    *
@@ -92,14 +91,14 @@ public function testPasswordNeedsUpdate() {
    *
    * @covers ::hash
    * @covers ::getCountLog2
-   * @covers ::check
+   * @covers ::verify
    * @covers ::needsRehash
    */
   public function testPasswordHashing() {
-    $this->assertSame($this->passwordHasher->getCountLog2($this->hashedPassword), PhpassHashedPassword::MIN_HASH_COUNT, 'Hashed password has the minimum number of log2 iterations.');
+    $this->assertSame($this->passwordHasher->getCountLog2($this->hashedPassword), Drupal7Password::MIN_HASH_COUNT);
     $this->assertNotEquals($this->hashedPassword, $this->md5HashedPassword, 'Password hashes not the same.');
-    $this->assertTrue($this->passwordHasher->check($this->password, $this->md5HashedPassword), 'Password check succeeds.');
-    $this->assertTrue($this->passwordHasher->check($this->password, $this->hashedPassword), 'Password check succeeds.');
+    $this->assertTrue($this->passwordHasher->verify($this->password, $this->md5HashedPassword), 'Password check succeeds.');
+    $this->assertTrue($this->passwordHasher->verify($this->password, $this->hashedPassword), 'Password check succeeds.');
     // Since the log2 setting hasn't changed and the user has a valid password,
     // userNeedsNewHash() should return FALSE.
     $this->assertFalse($this->passwordHasher->needsRehash($this->hashedPassword), 'Does not need a new hash.');
@@ -110,22 +109,22 @@ public function testPasswordHashing() {
    *
    * @covers ::hash
    * @covers ::getCountLog2
-   * @covers ::check
+   * @covers ::verify
    * @covers ::needsRehash
    */
   public function testPasswordRehashing() {
     // Increment the log2 iteration to MIN + 1.
-    $password_hasher = new PhpassHashedPassword(PhpassHashedPassword::MIN_HASH_COUNT + 1);
+    $password_hasher = new Drupal7Password(Drupal7Password::MIN_HASH_COUNT + 1);
     $this->assertTrue($password_hasher->needsRehash($this->hashedPassword), 'Needs a new hash after incrementing the log2 count.');
     // Re-hash the password.
     $rehashed_password = $password_hasher->hash($this->password);
-    $this->assertSame($password_hasher->getCountLog2($rehashed_password), PhpassHashedPassword::MIN_HASH_COUNT + 1, 'Re-hashed password has the correct number of log2 iterations.');
+    $this->assertSame($password_hasher->getCountLog2($rehashed_password), Drupal7Password::MIN_HASH_COUNT + 1, 'Re-hashed password has the correct number of log2 iterations.');
     $this->assertNotEquals($rehashed_password, $this->hashedPassword, 'Password hash changed again.');
 
     // Now the hash should be OK.
     $this->assertFalse($password_hasher->needsRehash($rehashed_password), 'Re-hashed password does not need a new hash.');
-    $this->assertTrue($password_hasher->check($this->password, $rehashed_password), 'Password check succeeds with re-hashed password.');
-    $this->assertTrue($this->passwordHasher->check($this->password, $rehashed_password), 'Password check succeeds with re-hashed password with original hasher.');
+    $this->assertTrue($password_hasher->verify($this->password, $rehashed_password), 'Password check succeeds with re-hashed password.');
+    $this->assertTrue($this->passwordHasher->verify($this->password, $rehashed_password), 'Password check succeeds with re-hashed password with original hasher.');
   }
 
   /**
@@ -175,7 +174,7 @@ public function providerLongPasswords() {
 /**
  * A fake class for tests.
  */
-class FakePhpassHashedPassword extends PhpassHashedPassword {
+class FakeDrupal7Password extends Drupal7Password {
 
   function __construct() {
     // Noop.
diff --git a/core/tests/Drupal/Tests/Core/Password/PhpPhpPasswordTest.php b/core/tests/Drupal/Tests/Core/Password/PhpPhpPasswordTest.php
new file mode 100644
index 0000000..7fb679c
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Password/PhpPhpPasswordTest.php
@@ -0,0 +1,162 @@
+<?php
+
+/**
+ * @file
+ * Contains Drupal\system\Tests\System\PhpPasswordTest.
+ */
+
+namespace Drupal\Tests\Core\Password;
+
+use Drupal\Core\Password\Drupal7Password;
+use Drupal\Core\Password\PhpPassword;
+use Drupal\Core\Password\PasswordInterface;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Unit tests for password hashing API.
+ *
+ * @coversDefaultClass \Drupal\Core\Password\Drupal7Password
+ * @group System
+ */
+class PhpPasswordTest extends UnitTestCase {
+
+  /**
+   * The raw password.
+   *
+   * @var string
+   */
+  protected $password;
+
+  /**
+   * The md5 hashed password.
+   *
+   * @var string
+   */
+  protected $md5Hash;
+
+  /**
+   * The hashed password.
+   *
+   * @var string
+   */
+  protected $hashedPassword;
+
+  /**
+   * The Drupal 7 hashed password.
+   *
+   * @var string
+   */
+  protected $d7Hash;
+
+  /**
+   * The password hasher under test.
+   *
+   * @var \Drupal\Core\Password\PasswordInterface
+   */
+  protected $passwordHasher;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $d7_hashing_service = new Drupal7Password(1);
+    $this->passwordHasher = new PhpPassword(4, $d7_hashing_service);
+    $this->password = $this->randomMachineName();
+    $this->md5Hash = md5($this->password);
+    $this->d7Hash = $d7_hashing_service->hash($this->password);
+  }
+
+  /**
+   * Test a password needs update.
+   *
+   * @covers ::needsRehash
+   */
+  public function testPasswordNeedsUpdate() {
+    // The md5 password should be flagged as needing an rehashing.
+    $this->assertTrue($this->passwordHasher->needsRehash($this->md5Hash));
+    // The Drupal 7 password should be flagged as needing an rehashing.
+    $this->assertTrue($this->passwordHasher->needsRehash($this->d7Hash));
+  }
+
+  /**
+   * Test password hashing.
+   *
+   * @covers ::hash
+   * @covers ::verify
+   * @covers ::needsRehash
+   */
+  public function testPasswordHashing() {
+    $this->hashedPassword = $this->passwordHasher->hash($this->password);
+
+    $this->assertNotEquals($this->hashedPassword, $this->md5Hash);
+    $this->assertNotEquals($this->hashedPassword, $this->d7Hash);
+
+    $this->assertTrue($this->passwordHasher->verify($this->password, $this->hashedPassword));
+    $this->assertFalse($this->passwordHasher->needsRehash($this->hashedPassword));
+  }
+
+  /**
+   * Tests password rehashing.
+   *
+   * @covers ::hash
+   * @covers ::check
+   * @covers ::needsRehash
+   */
+  public function testPasswordRehashing() {
+    // Increment the cost from 4 to 5.
+    $this->passwordHasher = new PhpPassword(5, new Drupal7Password(1));
+    $this->assertTrue($this->passwordHasher->needsRehash($this->hashedPassword));
+
+    // Re-hash the password.
+    $rehashed_password = $this->passwordHasher->hash($this->password);
+    $this->assertNotEquals($rehashed_password, $this->hashedPassword);
+
+    // Now the hash should be OK.
+    $this->assertFalse($this->passwordHasher->needsRehash($rehashed_password));
+    $this->assertTrue($this->passwordHasher->verify($this->password, $rehashed_password));
+  }
+
+  /**
+   * Verifies that passwords longer than 512 bytes are not hashed.
+   *
+   * @covers ::hash
+   *
+   * @dataProvider providerLongPasswords
+   */
+  public function testLongPassword($password, $allowed) {
+
+    $hashed_password = $this->passwordHasher->hash($password);
+
+    if ($allowed) {
+      $this->assertNotFalse($hashed_password);
+    }
+    else {
+      $this->assertFalse($hashed_password);
+    }
+  }
+
+  /**
+   * Provides the test matrix for testLongPassword().
+   */
+  public function providerLongPasswords() {
+    // '512 byte long password is allowed.'
+    $passwords['allowed'] = array(str_repeat('x', PasswordInterface::PASSWORD_MAX_LENGTH), TRUE);
+    // 513 byte long password is not allowed.
+    $passwords['too_long'] = array(str_repeat('x', PasswordInterface::PASSWORD_MAX_LENGTH + 1), FALSE);
+
+    // Check a string of 3-byte UTF-8 characters, 510 byte long password is
+    // allowed.
+    $len = floor(PasswordInterface::PASSWORD_MAX_LENGTH / 3);
+    $diff = PasswordInterface::PASSWORD_MAX_LENGTH % 3;
+    $passwords['utf8'] = array(str_repeat('€', $len), TRUE);
+    // 512 byte long password is allowed.
+    $passwords['ut8_extended'] = array($passwords['utf8'][0] . str_repeat('x', $diff), TRUE);
+
+    // Check a string of 3-byte UTF-8 characters, 513 byte long password is
+    // allowed.
+    $passwords['utf8_too_long'] = array(str_repeat('€', $len + 1), FALSE);
+    return $passwords;
+  }
+
+}