diff --git a/src/lib/Data.php b/src/lib/Data.php
index 3f380b0..6713767 100644
--- a/src/lib/Data.php
+++ b/src/lib/Data.php
@@ -9,7 +9,7 @@ class Data {
      * @return SQLite3 A new connection to the database
      */
     public static function getConnection(): SQLite3 {
-        $db = new SQLite3('../data/' . DATABASE_NAME);
+        $db = new SQLite3(implode(DIRECTORY_SEPARATOR, [__DIR__, '..', 'data', DATABASE_NAME]));
         $db->exec('PRAGMA foreign_keys = ON;');
         return $db;
     }
@@ -65,47 +65,6 @@ class Data {
         $db->close();
     }
 
-    /**
-     * Find a user by their ID
-     *
-     * @param string $email The e-mail address of the user to retrieve
-     * @return array|null The user information, or null if the user is not found
-     */
-    public static function findUserByEmail(string $email): ?array {
-        $db = self::getConnection();
-        try {
-            $query = $db->prepare('SELECT * FROM frc_user WHERE email = :email');
-            $query->bindValue(':email', $email);
-            $result = $query->execute();
-            if ($result) {
-                $user = $result->fetchArray(SQLITE3_ASSOC);
-                if ($user) return $user;
-                return null;
-            }
-            return null;
-        } finally {
-            $db->close();
-        }
-    }
-
-    /**
-     * Add a user
-     *
-     * @param string $email The e-mail address for the user
-     * @param string $password The user's password
-     */
-    public static function addUser(string $email, string $password): void {
-        $db = self::getConnection();
-        try {
-            $query = $db->prepare('INSERT INTO frc_user (email, password) VALUES (:email, :password)');
-            $query->bindValue(':email', $email);
-            $query->bindValue(':password', password_hash($password, PASSWORD_DEFAULT));
-            $query->execute();
-        } finally {
-            $db->close();
-        }
-    }
-
     /**
      * Parse/format a date/time from a string
      *
@@ -132,7 +91,7 @@ class Data {
         try {
             $query = $db->prepare('SELECT * FROM feed WHERE id = :id AND user_id = :user');
             $query->bindValue(':id', $feedId);
-            $query->bindValue(':user', $_REQUEST[Key::USER_ID]);
+            $query->bindValue(':user', $_SESSION[Key::USER_ID]);
             $result = $query->execute();
             return $result ? $result->fetchArray(SQLITE3_ASSOC) : false;
         } finally {
diff --git a/src/lib/Feed.php b/src/lib/Feed.php
index 3f2cbbc..79a9859 100644
--- a/src/lib/Feed.php
+++ b/src/lib/Feed.php
@@ -229,7 +229,7 @@ class Feed {
     private static function refreshFeed(string $url, SQLite3 $db): array {
         $feedQuery = $db->prepare('SELECT id FROM feed WHERE url = :url AND user_id = :user');
         $feedQuery->bindValue(':url',  $url);
-        $feedQuery->bindValue(':user', $_REQUEST[Key::USER_ID]);
+        $feedQuery->bindValue(':user', $_SESSION[Key::USER_ID]);
         $feedResult = $feedQuery->execute();
         $feedId = $feedResult ? $feedResult->fetchArray(SQLITE3_NUM)[0] : -1;
         if ($feedId < 0) return ['error' => "No feed for URL $url found"];
@@ -273,7 +273,7 @@ class Feed {
             INSERT INTO feed (user_id, url, title, updated_on, checked_on)
             VALUES (:user, :url, :title, :updated, :checked)
             SQL);
-        $query->bindValue(':user',    $_REQUEST[Key::USER_ID]);
+        $query->bindValue(':user',    $_SESSION[Key::USER_ID]);
         $query->bindValue(':url',     $feed['url']);
         $query->bindValue(':title',   self::eltValue($feed['channel'], 'title'));
         $query->bindValue(':updated', $feed['updated']);
@@ -300,7 +300,7 @@ class Feed {
         $query = $db->prepare('UPDATE feed SET url = :url WHERE id = :id AND user_id = :user');
         $query->bindValue(':url',  $url);
         $query->bindValue(':id',   $existing['id']);
-        $query->bindValue(':user', $_REQUEST[Key::USER_ID]);
+        $query->bindValue(':user', $_SESSION[Key::USER_ID]);
         $query->execute();
 
         return self::refreshFeed($url, $db);
@@ -312,7 +312,7 @@ class Feed {
      */
     public static function refreshAll(SQLite3 $db): array {
         $query = $db->prepare('SELECT url FROM feed WHERE user_id = :user');
-        $query->bindValue(':user', $_REQUEST[Key::USER_ID]);
+        $query->bindValue(':user', $_SESSION[Key::USER_ID]);
         $result = $query->execute();
         $url    = $result ? $result->fetchArray(SQLITE3_NUM) : false;
         if ($url) {
diff --git a/src/lib/Key.php b/src/lib/Key.php
index 39e7bfd..e1bf82a 100644
--- a/src/lib/Key.php
+++ b/src/lib/Key.php
@@ -2,10 +2,10 @@
 
 class Key {
 
-    /** @var string The $_REQUEST key for teh current user's e-mail address */
+    /** @var string The $_SESSION key for the current user's e-mail address */
     public const string USER_EMAIL = 'FRC_USER_EMAIL';
 
-    /** @var string The $_REQUEST key for the current user's ID */
+    /** @var string The $_SESSION key for the current user's ID */
     public const string USER_ID = 'FRC_USER_ID';
 
     /** @var string The $_REQUEST key for the array of user messages to display */
diff --git a/src/lib/Security.php b/src/lib/Security.php
index 7b1c7cf..c79ebed 100644
--- a/src/lib/Security.php
+++ b/src/lib/Security.php
@@ -14,38 +14,108 @@ class Security {
     /** @var int Require users to provide e-mail address and password */
     public const int MULTI_USER = 2;
 
+    /** @var string The e-mail address for the single user */
+    public const string SINGLE_USER_EMAIL = 'solouser@example.com';
+
+    /** @var string The password for the single user with no password */
+    private const string SINGLE_USER_PASSWORD = 'no-password-required';
+
     /**
-     * Verify that user is logged on
-     * @param bool $redirectIfAnonymous Whether to redirect the request if there is no user logged on
+     * Find a user by their ID
+     *
+     * @param string $email The e-mail address of the user to retrieve
+     * @param SQLite3 $db The data connection to use to retrieve the user
+     * @return array|false The user information, or null if the user is not found
      */
-    public static function verifyUser(bool $redirectIfAnonymous = true): void {
-        switch (SECURITY_MODEL) {
-            case self::SINGLE_USER:
-                $user = self::retrieveSingleUser();
-                break;
-            case self::SINGLE_USER_WITH_PASSWORD:
-                die('Single User w/ Password has not yet been implemented');
-            case self::MULTI_USER:
-                die('Multi-User Mode has not yet been implemented');
-            default:
-                die('Unrecognized security model (' . SECURITY_MODEL . ')');
-        }
-        if (!$user && $redirectIfAnonymous) {
-            header('/logon?returnTo=' . $_SERVER['REQUEST_URI'], true, HTTP_REDIRECT_TEMP);
-            die();
-        }
-        $_REQUEST[Key::USER_ID]    = $user['id'];
-        $_REQUEST[Key::USER_EMAIL] = $user['email'];
+    private static function findUserByEmail(string $email, SQLite3 $db): array|false {
+        $query = $db->prepare('SELECT * FROM frc_user WHERE email = :email');
+        $query->bindValue(':email', $email);
+        $result = $query->execute();
+        return $result ? $result->fetchArray(SQLITE3_ASSOC) : false;
     }
 
     /**
-     * Retrieve the single user
-     * @return array The user information for the single user
+     * Add a user
+     *
+     * @param string $email The e-mail address for the user
+     * @param string $password The user's password
+     * @param SQLite3 $db The data connection to use to add the user
      */
-    private static function retrieveSingleUser(): array {
-        $user = Data::findUserByEmail('solouser@example.com');
-        if ($user) return $user;
-        Data::addUser('solouser@example.com', 'no-password-required');
-        return Data::findUserByEmail('solouser@example.com');
+    public static function addUser(string $email, string $password, SQLite3 $db): void {
+        $query = $db->prepare('INSERT INTO frc_user (email, password) VALUES (:email, :password)');
+        $query->bindValue(':email',    $email);
+        $query->bindValue(':password', password_hash($password, PASSWORD_DEFAULT));
+        $query->execute();
+    }
+
+    /**
+     * Verify a user's password
+     *
+     * @param array $user The user information retrieved from the database
+     * @param string $password The password provided by the user
+     * @param string|null $returnTo The URL to which the user should be redirected
+     * @param SQLite3 $db The database connection to use to verify the user's credentials
+     */
+    private static function verifyPassword(array $user, string $password, ?string $returnTo, SQLite3 $db): void {
+        if (password_verify($password, $user['password'])) {
+            if (password_needs_rehash($user['password'], PASSWORD_DEFAULT)) {
+                $rehash = $db->prepare('UPDATE frc_user SET password = :hash WHERE id = :id');
+                $rehash->bindValue(':hash', password_hash($password, PASSWORD_DEFAULT));
+                $rehash->bindValue(':id',   $user['id']);
+                $rehash->execute();
+            }
+            $_SESSION[Key::USER_ID]    = $user['id'];
+            $_SESSION[Key::USER_EMAIL] = $user['email'];
+            frc_redirect($returnTo ?? '/');
+        }
+    }
+
+    /**
+     * Log on a user with e-mail address and password
+     *
+     * @param string $email The e-mail address for the user
+     * @param string $password The password provided by the user
+     * @param string|null $returnTo The URL to which the user should be redirected
+     * @param SQLite3 $db The database connection to use to verify the user's credentials
+     */
+    public static function logOnUser(string $email, string $password, ?string $returnTo, SQLite3 $db): void {
+        $user = self::findUserByEmail($email, $db);
+        if ($user) self::verifyPassword($user, $password, $returnTo, $db);
+        add_error('Invalid credentials; log on unsuccessful');
+    }
+
+    /**
+     * Log on the single user
+     *
+     * @param SQLite3 $db The data connection to use to retrieve the user
+     */
+    private static function logOnSingleUser(SQLite3 $db): void {
+        $user = self::findUserByEmail(self::SINGLE_USER_EMAIL, $db);
+        if (!$user) {
+            self::addUser(self::SINGLE_USER_EMAIL, self::SINGLE_USER_PASSWORD, $db);
+            $user = self::findUserByEmail(self::SINGLE_USER_EMAIL, $db);
+        }
+        self::verifyPassword($user, self::SINGLE_USER_PASSWORD, $_GET['returnTo'], $db);
+    }
+
+    /**
+     * Verify that user is logged on
+     *
+     * @param SQLite3 $db The data connection to use if required
+     * @param bool $redirectIfAnonymous Whether to redirect the request if there is no user logged on
+     */
+    public static function verifyUser(SQLite3 $db, bool $redirectIfAnonymous = true): void {
+        if (array_key_exists(Key::USER_ID, $_SESSION)) return;
+
+        if (SECURITY_MODEL == self::SINGLE_USER) self::logOnSingleUser($db);
+
+        if (SECURITY_MODEL != self::SINGLE_USER_WITH_PASSWORD && SECURITY_MODEL != self::MULTI_USER) {
+            die('Unrecognized security model (' . SECURITY_MODEL . ')');
+        }
+
+        if ($redirectIfAnonymous) {
+            header("Location: /user/log-on?returnTo={$_SERVER['REQUEST_URI']}", true, 307);
+            die();
+        }
     }
 }
diff --git a/src/public/assets/style.css b/src/public/assets/style.css
index 86bd961..9518ea3 100644
--- a/src/public/assets/style.css
+++ b/src/public/assets/style.css
@@ -57,7 +57,10 @@ article {
         padding: .5rem;
     }
 }
-input[type=url], input[type=text] {
+input[type=url],
+input[type=text],
+input[type=email],
+input[type=password] {
     width: 50%;
     font-size: 1rem;
     padding: .25rem;
diff --git a/src/public/feed.php b/src/public/feed.php
index 85446c2..80f985a 100644
--- a/src/public/feed.php
+++ b/src/public/feed.php
@@ -7,10 +7,10 @@
 
 include '../start.php';
 
-Security::verifyUser();
+$db = Data::getConnection();
+Security::verifyUser($db);
 
-$feedId = array_key_exists('id', $_GET) ? $_GET['id'] : '';
-$db     = Data::getConnection();
+$feedId = $_GET['id'] ?? '';
 
 if ($_SERVER['REQUEST_METHOD'] == 'POST') {
     $isNew = $_POST['id'] == 'new';
@@ -31,7 +31,7 @@ if ($_SERVER['REQUEST_METHOD'] == 'POST') {
 
 if ($feedId == 'new') {
     $title = 'Add RSS Feed';
-    $feed = [ 'id' => $_GET['id'], 'url' => '' ];
+    $feed = [ 'id' => $_GET['id'], 'url' => ''];
 } else {
     $title = 'Edit RSS Feed';
     if ($feedId == 'error') {
diff --git a/src/public/index.php b/src/public/index.php
index 6bcb14f..9b75399 100644
--- a/src/public/index.php
+++ b/src/public/index.php
@@ -7,9 +7,8 @@
 
 include '../start.php';
 
-Security::verifyUser();
-
 $db = Data::getConnection();
+Security::verifyUser($db);
 
 if (array_key_exists('refresh', $_GET)) {
     $refreshResult = Feed::refreshAll($db);
diff --git a/src/public/item.php b/src/public/item.php
index 1e98bd5..ee4a714 100644
--- a/src/public/item.php
+++ b/src/public/item.php
@@ -8,9 +8,8 @@
 
 include '../start.php';
 
-Security::verifyUser();
-
 $db = Data::getConnection();
+Security::verifyUser($db);
 
 if ($_SERVER['REQUEST_METHOD'] == 'POST') {
     // "Keep as New" button sends a POST request to reset the is_read flag before going back to the list of unread items
@@ -20,7 +19,7 @@ if ($_SERVER['REQUEST_METHOD'] == 'POST') {
          WHERE item.id = :id AND feed.user_id = :user
         SQL);
     $isValidQuery->bindValue(':id',   $_POST['id']);
-    $isValidQuery->bindValue(':user', $_REQUEST[Key::USER_ID]);
+    $isValidQuery->bindValue(':user', $_SESSION[Key::USER_ID]);
     $isValidResult = $isValidQuery->execute();
     if ($isValidResult && $isValidResult->fetchArray(SQLITE3_NUM)[0] == 1) {
         $keepUnread = $db->prepare('UPDATE item SET is_read = 0 WHERE id = :id');
@@ -39,7 +38,7 @@ $query = $db->prepare(<<<'SQL'
        AND feed.user_id = :user
     SQL);
 $query->bindValue(':id',   $_GET['id']);
-$query->bindValue(':user', $_REQUEST[Key::USER_ID]);
+$query->bindValue(':user', $_SESSION[Key::USER_ID]);
 $result = $query->execute();
 $item = $result ? $result->fetchArray(SQLITE3_ASSOC) : false;
 
diff --git a/src/public/user/log-off.php b/src/public/user/log-off.php
new file mode 100644
index 0000000..5ba1f32
--- /dev/null
+++ b/src/public/user/log-off.php
@@ -0,0 +1,10 @@
+<?php
+/**
+ * User Log Off Page
+ */
+
+include '../../start.php';
+
+if (array_key_exists(Key::USER_ID, $_SESSION)) session_destroy();
+
+frc_redirect('/');
diff --git a/src/public/user/log-on.php b/src/public/user/log-on.php
new file mode 100644
index 0000000..64f4aab
--- /dev/null
+++ b/src/public/user/log-on.php
@@ -0,0 +1,39 @@
+<?php
+include '../../start.php';
+
+$db = Data::getConnection();
+Security::verifyUser($db, redirectIfAnonymous: false);
+
+// Users already logged on have no need of this page
+if (array_key_exists(Key::USER_ID, $_SESSION)) frc_redirect('/');
+
+if ($_SERVER['REQUEST_METHOD'] == 'POST') {
+    Security::logOnUser($_POST['email'] ?? '', $_POST['password'], $_POST['returnTo'], $db);
+    // If we're still here, something didn't work; preserve the returnTo parameter
+    $_GET['returnTo'] = $_POST['returnTo'];
+}
+
+$isSingle = SECURITY_MODEL == Security::SINGLE_USER_WITH_PASSWORD;
+
+page_head('Log On'); ?>
+<h1>Log On</h1>
+<article>
+    <form method=POST action=/user/log-on hx-post=/user/log-on><?php
+        if (($_GET['returnTo'] ?? '') != '') { ?>
+            <input type=hidden name=returnTo value="<?=$_GET['returnTo']?>"><?php
+        }
+        if (!$isSingle) { ?>
+            <label>
+                E-mail Address
+                <input type=email name=email required autofocus>
+            </label><br><?php
+        } ?>
+        <label>
+            Password
+            <input type=password name=password required<?=$isSingle ? ' autofocus' : ''?>>
+        </label><br>
+        <button type=submit>Log On</button>
+    </form>
+</article><?php
+page_foot();
+$db->close();
diff --git a/src/start.php b/src/start.php
index 48701ab..249c21f 100644
--- a/src/start.php
+++ b/src/start.php
@@ -14,6 +14,12 @@ require 'user-config.php';
 
 Data::ensureDb();
 
+session_start([
+    'name'            => 'FRCSESSION',
+    'use_strict_mode' => true,
+    'cookie_httponly' => true,
+    'cookie_samesite' => 'Strict']);
+
 /**
  * Add a message to be displayed at the top of the page
  *
@@ -59,20 +65,20 @@ function page_head(string $title): void {
 <header>
     <a class=title href="/">Feed Reader Central</a>
     <div><?php
-        if (array_key_exists(Key::USER_ID, $_REQUEST)) {
-            echo '<a href=/feed?id=new>Add Feed</a>';
-            if ($_REQUEST[Key::USER_EMAIL] != 'solouser@example.com') echo " | {$_REQUEST[Key::USER_EMAIL]}";
+        if (array_key_exists(Key::USER_ID, $_SESSION)) {
+            echo '<a href=/feed?id=new>Add Feed</a> | <a href=/user/log-off>Log Off</a>';
+            if ($_SESSION[Key::USER_EMAIL] != Security::SINGLE_USER_EMAIL) echo " | {$_SESSION[Key::USER_EMAIL]}";
+        } else {
+            echo '<a href=/user/log-on>Log On</a>';
         } ?>
     </div>
 </header>
 <main hx-target=this><?php
-    if (array_key_exists(Key::USER_MSG, $_REQUEST)) {
-        foreach ($_REQUEST[Key::USER_MSG] as $msg) { ?>
-            <div>
-                <?=$msg['level'] == 'INFO' ? '' : "<strong>{$msg['level']}</strong><br>"?>
-                <?=$msg['message']?>
-            </div><?php
-        }
+    foreach ($_REQUEST[Key::USER_MSG] ?? [] as $msg) { ?>
+        <div>
+            <?=$msg['level'] == 'INFO' ? '' : "<strong>{$msg['level']}</strong><br>"?>
+            <?=$msg['message']?>
+        </div><?php
     }
 }
 
@@ -81,6 +87,7 @@ function page_head(string $title): void {
  */
 function page_foot(): void {
     ?></main></body></html><?php
+    session_commit();
 }
 
 /**
@@ -94,8 +101,8 @@ function frc_redirect(string $value): void {
         http_response_code(400);
         die();
     }
-    header("Location: $value");
-    http_response_code(303);
+    session_commit();
+    header("Location: $value", true, 303);
     die();
 }
 
diff --git a/src/user-config.php b/src/user-config.php
index 55af358..a89cefe 100644
--- a/src/user-config.php
+++ b/src/user-config.php
@@ -11,8 +11,6 @@
  * - Security::SINGLE_USER (no e-mail required, does not require a password)
  * - Security::SINGLE_USER_WITH_PASSWORD (no e-mail required, does require a password)
  * - Security::MULTI_USER (e-mail and password required for all users)
- *
- * (NOTE THAT ONLY SINGLE_USER IS CURRENTLY IMPLEMENTED)
  */
 const SECURITY_MODEL = Security::SINGLE_USER;