diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -2112,6 +2112,7 @@
     'PhabricatorSavedQuery' => 'applications/search/storage/PhabricatorSavedQuery.php',
     'PhabricatorSavedQueryQuery' => 'applications/search/query/PhabricatorSavedQueryQuery.php',
     'PhabricatorScopedEnv' => 'infrastructure/env/PhabricatorScopedEnv.php',
+    'PhabricatorScryptPasswordHasher' => 'infrastructure/util/password/PhabricatorScryptPasswordHasher.php',
     'PhabricatorSearchAbstractDocument' => 'applications/search/index/PhabricatorSearchAbstractDocument.php',
     'PhabricatorSearchApplication' => 'applications/search/application/PhabricatorSearchApplication.php',
     'PhabricatorSearchApplicationSearchEngine' => 'applications/search/query/PhabricatorSearchApplicationSearchEngine.php',
@@ -5012,6 +5013,7 @@
       'PhabricatorPolicyInterface',
     ),
     'PhabricatorSavedQueryQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
+    'PhabricatorScryptPasswordHasher' => 'PhabricatorPasswordHasher',
     'PhabricatorSearchApplication' => 'PhabricatorApplication',
     'PhabricatorSearchApplicationSearchEngine' => 'PhabricatorApplicationSearchEngine',
     'PhabricatorSearchAttachController' => 'PhabricatorSearchBaseController',
diff --git a/src/infrastructure/util/password/PhabricatorScryptPasswordHasher.php b/src/infrastructure/util/password/PhabricatorScryptPasswordHasher.php
new file mode 100644
--- /dev/null
+++ b/src/infrastructure/util/password/PhabricatorScryptPasswordHasher.php
@@ -0,0 +1,129 @@
+<?php
+
+final class PhabricatorScryptPasswordHasher
+  extends PhabricatorPasswordHasher {
+
+  public function getHumanReadableName() {
+    return pht('scrypt');
+  }
+
+  public function getHashName() {
+    return 'scrypt';
+  }
+
+  public function getHashLength() {
+    // 'logN', 'r', and 'p' are each 3 bytes.
+    // There are four '|' separators, one byte each.
+    // The salt is 16 bytes.
+    // The hash is 40 bytes, but converted to a hex string, so 80 bytes total.
+    // So: 3 + 3 + 3 + 4 + 16 + (40*2) = 109
+    return 109;
+  }
+
+  public function canHashPasswords() {
+    return extension_loaded('scrypt') && function_exists('scrypt');
+  }
+
+  public function getInstallInstructions() {
+    return pht('Install the `scrypt` extension via PECL/PEAR.');
+  }
+
+  public function getStrength() {
+    return 4.0;
+  }
+
+  public function getHumanReadableStrength() {
+    return pht('Great');
+  }
+
+  protected function getPasswordHash(PhutilOpaqueEnvelope $envelope) {
+    list($log_n, $r, $p) = $this->getScryptParams();
+    $salt = Filesystem::readRandomCharacters(16);
+
+    return new PhutilOpaqueEnvelope(
+      $this->createHash($envelope->openEnvelope(), $salt, $log_n, $r, $p));
+  }
+
+  protected function verifyPassword(
+    PhutilOpaqueEnvelope $password,
+    PhutilOpaqueEnvelope $hash) {
+    return $this->verifyPass($password->openEnvelope(), $hash->openEnvelope());
+  }
+
+  protected function canUpgradeInternalHash(PhutilOpaqueEnvelope $hash) {
+    $info = $this->getParams($hash->openEnvelope());
+
+    // NOTE: If the costs don't match -- even if the new cost is lower than
+    // the old cost -- count this as an upgrade. This allows costs to be
+    // adjusted down and hashing to be migrated toward the new cost if costs
+    // are ever configured too high for some reason.
+
+    if ($info !== $this->getScryptParams()) {
+      return true;
+    }
+
+    return false;
+  }
+
+  private function getScryptParams() {
+    // Recommended interactive scrypt parameters (log2(N), r, p)
+    //   - NOTE: /n/ is specified as log2(N)
+    //
+    // Running time is proportional to `r`, `n`, and `p`.
+    //
+    // Memory usage is approximately `128*r*n` bytes. Default settings are
+    // `128*(2^14)*8 = 16MB`.
+    //
+    // `p` can be independently tuned to influence running time since it has
+    // low influence on memory use.
+    return array(14, 8, 1);
+  }
+
+  /**
+   * Verify a password against a serialized hash
+   */
+  private function verifyPass($pass, $hash) {
+    list($log_n, $r, $p, $salt, $raw_hash) = $this->separateHash($hash);
+
+    $pass_hash = $this->createHash($pass, $salt, $log_n, $r, $p);
+    return $pass_hash === $hash; /* TODO FIXME: constant time comparison? */
+  }
+
+  /**
+   * Create a fully 'serialized' hash with included parameters.
+   *
+   * @phutil-external-symbol function scrypt
+   */
+  private function createHash($raw_input, $salt, $log_n, $r, $p) {
+    $hash = scrypt(
+      $raw_input, $salt,
+      pow(2, intval($log_n)), intval($r), intval($p),
+      40);
+
+    // Format numbers to three decimal places for accurate hash
+    // lengths, since the 40 byte output and 16 byte salt are
+    // statically known. (Someone could set `p = 10` for example,
+    // which would break things with naive formatting.)
+    $log_n = sprintf('%03d', $log_n);
+    $r     = sprintf('%03d', $r);
+    $p     = sprintf('%03d', $p);
+    return implode('|', array($log_n, $r, $p, $salt, $hash));
+  }
+
+  /**
+   * Get the parameters used for a hashed password.
+   */
+  private function getParams($hash) {
+    list($log_n, $r, $p, $salt, $raw_hash) = $this->separateHash($hash);
+    return array($log_n, $r, $p);
+  }
+
+  /**
+   * Split a hashed password into its internal components.
+   */
+  private function separateHash($hash) {
+    list($log_n, $r, $p, $salt, $raw_hash) = explode('|', $hash);
+    return array(intval($log_n), intval($r), intval($p), $salt, $raw_hash);
+  }
+
+}