某人觉得md5运算的块要单独提出来，后来又提到其实不做md5也一样，另外的某人一琢磨也对，就提交了

lib/wechat.js

@@ -139,12 +139,8 @@ var respond = function (handler) {
         var storage = req.sessionStore;
         var _end = res.end;
         var userOpenid = message.FromUserName;
-	    var serviceOpenid = message.ToUserName;
-	    var _str = serviceOpenid + ":" + userOpenid;
-	    var _hash = crypto.createHash("md5");
-	    _hash.update(_str);
-	    var _hashmsg = _hash.digest('hex');
-	    var hashid = _hashmsg.toString();
+        var SPOpenid = message.ToUserName;
+        var mixId = SPOpenid + ":" + userOpenid;
         res.end = function () {
           _end.apply(res, arguments);
           if (req.wxsession) {
@@ -172,12 +168,12 @@ var respond = function (handler) {
           res.reply.apply(res, arguments);
         };
 
-        storage.get(hashid, function (err, session) {
+        storage.get(mixId, function (err, session) {
           if (!session) {
-            req.wxsession = new Session(hashid, req);
+            req.wxsession = new Session(mixId, req);
             req.wxsession.cookie = req.session.cookie;
           } else {
-            req.wxsession = new Session(hashid, req, session);
+            req.wxsession = new Session(mixId, req, session);
           }
           done();
         });