diff --git a/lib/microid.php b/lib/microid.php
new file mode 100644
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--- /dev/null
+++ b/lib/microid.php
@@ -0,0 +1,97 @@
+<?php
+/**
+ * Laconica, the distributed open-source microblogging tool
+ *
+ * Microid class
+ *
+ * PHP version 5
+ *
+ * LICENCE: This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @category  ID
+ * @package   Laconica
+ * @author    Evan Prodromou <evan@controlyourself.ca>
+ * @copyright 2008 Control Yourself, Inc.
+ * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
+ * @link      http://laconi.ca/
+ */
+
+if (!defined('LACONICA')) {
+    exit(1);
+}
+
+/**
+ * A class for microids
+ *
+ * @category ID
+ * @package  Laconica
+ * @author   Evan Prodromou <evan@controlyourself.ca>
+ * @license  http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
+ * @link     http://laconi.ca/
+ * @see      http://microid.org/
+ */
+
+class Microid
+{
+    /** Agent part of the ID. */
+
+    var $agent = null;
+
+    /** Resource part of the ID. */
+
+    var $resource = null;
+
+    /**
+     * Constructor
+     *
+     * @param string $agent    Agent of the ID
+     * @param string $resource Resource part
+     */
+
+    function __construct($agent, $resource)
+    {
+        $this->agent    = $agent;
+        $this->resource = $resource;
+
+    }
+
+    /**
+     * Generate a MicroID string
+     *
+     * @return string MicroID for agent and resource
+     */
+
+    function toString()
+    {
+        $agent_proto    = $this->_getProto($this->agent);
+        $resource_proto = $this->_getProto($this->resource);
+
+        return $agent_proto.'+'.$resource_proto.':sha1:'.
+          sha1(sha1($this->agent).sha1($this->resource));
+    }
+
+    /**
+     * Utility for getting the protocol part of a URI
+     *
+     * @param string $uri URI to parse
+     *
+     * @return string scheme part of the URI
+     */
+
+    function _getProto($uri)
+    {
+        $colon = strpos($uri, ':');
+        return substr($uri, 0, $colon);
+    }
+}