diff --git a/phpgwapi/inc/class.egw_sharing.inc.php b/phpgwapi/inc/class.egw_sharing.inc.php
index 28c8474da8..ebcc274211 100644
--- a/phpgwapi/inc/class.egw_sharing.inc.php
+++ b/phpgwapi/inc/class.egw_sharing.inc.php
@@ -24,8 +24,11 @@ class egw_sharing
 {
 	/**
 	 * Length of base64 encoded token (real length is only 3/4 of it)
+	 *
+	 * Dropbox uses just 15 chars (letters/numbers 5-6 bit), php sessions use 32 chars (hex = 4bits),
+	 * so 32 chars of base64 = 6bits should be plenty.
 	 */
-	const TOKEN_LENGTH = 64;
+	const TOKEN_LENGTH = 32;
 
 	/**
 	 * Name of table used for storing tokens
@@ -237,9 +240,12 @@ class egw_sharing
 	public static function token()
 	{
 		// generate random token (using oppenssl if available otherwise mt_rand based auth::randomstring)
-		$token = function_exists('openssl_random_pseudo_bytes') ?
-			base64_encode(openssl_random_pseudo_bytes(3*self::TOKEN_LENGTH/4)) :
-			auth::randomstring(self::TOKEN_LENGTH);
+		do {
+			$token = function_exists('openssl_random_pseudo_bytes') ?
+				base64_encode(openssl_random_pseudo_bytes(3*self::TOKEN_LENGTH/4)) :
+				auth::randomstring(self::TOKEN_LENGTH);
+			// base64 can contain chars not allowed in our vfs-urls eg. / or #
+		} while ($token != egw_vfs::encodePathComponent($token));
 
 		return $token;
 	}
@@ -276,7 +282,7 @@ class egw_sharing
 			$path = 'vfs://default'.($path[0] == '/' ? '' : '/').$path;
 		}
 		// check if file exists and is readable
-		if (!file_exists($path) || is_readable($path))
+		if (!file_exists($path) || !is_readable($path))
 		{
 			throw new egw_exception_not_found("'$path' NOT found!");
 		}
@@ -323,7 +329,9 @@ class egw_sharing
 					$tmp_file = egw_vfs::concat($user_tmp, ($n?$n.'.':'').egw_vfs::basename($name));
 				}
 				while(!(is_dir($path) && egw_vfs::mkdir($tmp_file) ||
-					!is_dir($path) && ($fp = egw_vfs::fopen($tmp_file, 'x'))) && $n++ < 100);
+					!is_dir($path) && (!egw_vfs::file_exists($tmp_file) && ($fp = egw_vfs::fopen($tmp_file, 'x')) ||
+						// do not copy identical files again to users tmp dir, just re-use them
+						egw_vfs::file_exists($tmp_file) && egw_vfs::compare(egw_vfs::PREFIX.$tmp_file, $path))) && $n++ < 100);
 
 				if ($n >= 100)
 				{
@@ -340,6 +348,13 @@ class egw_sharing
 				$path2tmp[$path] = $tmp_file;
 
 				$path = $tmp_file;
+
+				// if not already installed, install periodic cleanup of tmp files
+				$async = new asyncservice();
+				if (!$async->read('egw_sharing-tmp-cleanup'))
+				{
+					$async->set_timer(array('day' => 28),'egw_sharing-tmp_cleanup','egw_sharing::tmp_cleanup',null);
+				}
 			}
 
 			$i = 0;
@@ -366,6 +381,28 @@ class egw_sharing
 		return $share;
 	}
 
+	/**
+	 * Periodic (monthly) cleanup of temp. sharing files
+	 */
+	public static function tmp_cleanup()
+	{
+		try {
+			egw_vfs::$is_root = true;
+			/* not yet ready
+			egw_vfs::find('/home', array(
+				'path_preg' => '|^/home/[^/]+/.tmp',
+				'maxdepth' => 3,
+			), function($path, $stat)
+			{
+				error_log(__METHOD__."() path=$path");
+			});*/
+		}
+		catch (Exception $e) {
+			unset($e);
+		}
+		egw_vfs::$is_root = false;
+	}
+
 	/**
 	 * Generate link from share or share-token
 	 *
diff --git a/phpgwapi/inc/class.egw_vfs.inc.php b/phpgwapi/inc/class.egw_vfs.inc.php
index b72c52fc3e..65dd99d9c7 100644
--- a/phpgwapi/inc/class.egw_vfs.inc.php
+++ b/phpgwapi/inc/class.egw_vfs.inc.php
@@ -2005,6 +2005,36 @@ class egw_vfs extends vfs_stream_wrapper
 		if (self::LOG_LEVEL > 1 || !$ret && self::LOG_LEVEL) error_log(__METHOD__."($tmp_name, $target, ".array2string($props).") returning ".array2string($ret));
 		return $ret;
 	}
+
+	/**
+	 * Compare two files from vfs or local file-system for identical content
+	 *
+	 * VFS files must use URL, to be able to distinguish them eg. from temp. files!
+	 *
+	 * @param string $file1 vfs-url or local path, eg. /tmp/some-file.txt or vfs://default/home/user/some-file.txt
+	 * @param string $file2 -- " --
+	 * @return boolean true: if files are identical, false: if not or file not found
+	 */
+	public static function compare($file1, $file2)
+	{
+		if (filesize($file1) != filesize($file2) ||
+			!($fp1 = fopen($file1, 'r')) || !($fp2 = fopen($file2, 'r')))
+		{
+			//error_log(__METHOD__."($file1, $file2) returning FALSE (different size)");
+			return false;
+		}
+		while (($read1 = fread($fp1, 8192)) !== false &&
+			($read2 = fread($fp2, 8192)) !== false &&
+			$read1 === $read2 && !feof($fp1) && !feof($fp2))
+		{
+			// just loop until we find a difference
+		}
+
+		fclose($fp1);
+		fclose($fp2);
+		//error_log(__METHOD__."($file1, $file2) returning ".array2string($read1 === $read2)." (content differs)");
+		return $read1 === $read2;
+	}
 }
 
 egw_vfs::init_static();