diff --git a/hgext/bookmarks.py b/hgext/bookmarks.py
--- a/hgext/bookmarks.py
+++ b/hgext/bookmarks.py
@@ -30,7 +30,7 @@
 
 from mercurial.i18n import _
 from mercurial.node import nullid, nullrev, hex, short
-from mercurial import util, commands, localrepo, repair, extensions
+from mercurial import util, commands, localrepo, repair, extensions, changegroup
 import os
 
 def write(repo):
@@ -316,6 +316,14 @@
     setcurrent(repo, rev)
     return res
 
+def listkey(repo):
+    return ('expected', 'actually')
+
+def pushkey(repo, values):
+    repo.ui.warn("pushed " + str(values) + "\n")
+
+changegroup.keyhandlers['bookmarks'] = listkey, pushkey
+
 cmdtable = {
     "bookmarks":
         (bookmark,
diff --git a/mercurial/changegroup.py b/mercurial/changegroup.py
--- a/mercurial/changegroup.py
+++ b/mercurial/changegroup.py
@@ -9,6 +9,10 @@
 import util
 import struct, os, bz2, zlib, tempfile
 
+# format per handler:
+# 'key' : (listkey-handler, pushkey-handler)
+keyhandlers = {}
+
 def getchunk(source):
     """return the next chunk from changegroup 'source' as a string"""
     d = source.read(4)
diff --git a/mercurial/hgweb/protocol.py b/mercurial/hgweb/protocol.py
--- a/mercurial/hgweb/protocol.py
+++ b/mercurial/hgweb/protocol.py
@@ -5,7 +5,7 @@
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
-import cStringIO, zlib, tempfile, errno, os, sys, urllib, copy
+import cStringIO, zlib, tempfile, errno, os, sys, urllib, copy, json
 from mercurial import util, streamclone
 from mercurial.node import bin, hex
 from mercurial import changegroup as changegroupmod
@@ -17,11 +17,11 @@
 __all__ = [
    'lookup', 'heads', 'branches', 'between', 'changegroup',
    'changegroupsubset', 'capabilities', 'unbundle', 'stream_out',
-   'branchmap',
+   'branchmap', 'listkeys', 'pushkeys'
 ]
 
 HGTYPE = 'application/mercurial-0.1'
-basecaps = 'lookup changegroupsubset branchmap'.split()
+basecaps = 'lookup changegroupsubset branchmap pushkeys'.split()
 
 def lookup(repo, req):
     try:
@@ -206,3 +206,37 @@
             yield chunk
     except streamclone.StreamException, inst:
         yield str(inst)
+
+def listkeys(repo, req):
+    import pdb
+    if req.env['REQUEST_METHOD'] != 'POST':
+        # TODO: HTTP METHOD NOT DEFINED
+        raise ErrorResponse(HTTP_METHOD_NOT_ALLOWED, 'Not allowed')
+    print "i'm going to read"
+    pdb.set_trace()
+    data = req.read()
+    print "i got my data "
+    if not data:
+        rsp = keyhandlers.keys()
+    else:
+        obj = json.load(req)
+        rsp = {}
+        for ns in obj:
+            if ns in keyhandlers and keyhandlers[ns][0]:
+                rsp[ns] = keyhandlers[ns][0]
+    req.respond(HTTP_OK, 'application/json')
+    return json.dumps(rsp, ensure_ascii=True)
+
+def pushkeys(repo, req):
+    if req.env['REQUEST_METHOD'] != 'POST':
+        raise ErrorResponse(HTTP_METHOD_NOT_ALLOWED, 'Not allowed')
+    data = req.read()[0].strip()
+    if not data:
+        raise ErrorResponse(HTTP_BAD_REQUEST, 'Require data')
+    rsp = {}
+    obj = json.loads(data)
+    for ns, values in obj.iteritems():
+        if ns in keyhandlers and keyhandlers[ns][1]:
+            rsp[ns] = keyhandlers[ns][1](values)
+    req.respond(HTTP_OK, 'application/json')
+    return json.dumps(rsp, ensure_ascii=True)
diff --git a/mercurial/httprepo.py b/mercurial/httprepo.py
--- a/mercurial/httprepo.py
+++ b/mercurial/httprepo.py
@@ -9,7 +9,7 @@
 from node import bin, hex, nullid
 from i18n import _
 import repo, changegroup, statichttprepo, error, url, util
-import os, urllib, urllib2, urlparse, zlib, httplib
+import os, urllib, urllib2, urlparse, zlib, httplib, json
 import errno, socket
 import encoding
 
@@ -195,6 +195,17 @@
         f = self.do_cmd("changegroup", roots=n)
         return util.chunkbuffer(zgenerator(f))
 
+    def pushkeys(self, data):
+        f = self.do_cmd("listkeys", json.loads(data))
+        self.ui.warn(f)
+        return util.chunkbuffer(zgenerator(f))
+
+    def listkeys(self, namespaces=None):
+        f = self.do_read("listkeys", data=json.dumps(namespaces,
+            ensure_ascii=True), headers={'Content-Type': 'application/json'})
+        self.ui.status(f)
+        return json.loads(f)
+
     def changegroupsubset(self, bases, heads, source):
         self.requirecap('changegroupsubset', _('look up remote changes'))
         baselst = " ".join([hex(n) for n in bases])
diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
--- a/mercurial/localrepo.py
+++ b/mercurial/localrepo.py
@@ -15,11 +15,12 @@
 import merge as merge_
 import tags as tags_
 from lock import release
-import weakref, stat, errno, os, time, inspect
+from changegroup import keyhandlers
+import weakref, stat, errno, os, time, inspect, json
 propertycache = util.propertycache
 
 class localrepository(repo.repository):
-    capabilities = set(('lookup', 'changegroupsubset', 'branchmap'))
+    capabilities = set(('lookup', 'changegroupsubset', 'branchmap', 'pushkeys'))
     supported = set('revlogv1 store fncache shared'.split())
 
     def __init__(self, baseui, path=None, create=0):
@@ -1449,6 +1450,8 @@
 
             if not fetch:
                 self.ui.status(_("no changes found\n"))
+                if remote.capable('pushkeys'):
+                    self.pullkeys(remote)
                 return 0
 
             if heads is None and remote.capable('changegroupsubset'):
@@ -1462,7 +1465,10 @@
                                        "other repository doesn't support "
                                        "changegroupsubset."))
                 cg = remote.changegroupsubset(fetch, heads, 'pull')
-            return self.addchangegroup(cg, 'pull', remote.url())
+            res = self.addchangegroup(cg, 'pull', remote.url())
+            if remote.capable('pushkeys'):
+                self.pullkeys(remote)
+            return res
         finally:
             lock.release()
 
@@ -1476,8 +1482,12 @@
         # servers, http servers).
 
         if remote.capable('unbundle'):
-            return self.push_unbundle(remote, force, revs)
-        return self.push_addchangegroup(remote, force, revs)
+            res = self.push_unbundle(remote, force, revs)
+        else:
+            res = self.push_addchangegroup(remote, force, revs)
+        if remote.capable('pushkeys'):
+            self.pushkeysremote(remote)
+        return res
 
     def prepush(self, remote, force, revs):
         '''Analyze the local and remote repositories and determine which
@@ -1618,6 +1628,48 @@
             return remote.unbundle(cg, remote_heads, 'push')
         return ret[1]
 
+    def listkeys(self, namespaces=None):
+        if not namespaces:
+            return keyhandlers.keys()
+        rsp = {}
+        for ns in namespaces:
+            if ns in keyhandlers and keyhandlers[ns][0]:
+                rsp[ns] = keyhandlers[ns][0](self)
+        return rsp
+
+    def pushkeys(self, data):
+        rsp = {}
+        for ns, values in data.iteritems():
+            if ns in keyhandlers and keyhandlers[ns][0]:
+                rsp[ns] = keyhandlers[ns][0](self)
+        return rsp
+
+    def pushkeysremote(self, remote):
+        """helper function to be called from push()"""
+        req = {}
+        for ns in remote.listkeys():
+            if ns in keyhandlers and keyhandlers[ns][0]:
+                req[ns] = keyhandlers[ns][0](self)
+        obj = remote.pushkeys(req)
+        for ns, error in obj.iteritems():
+            if error:
+                self.ui.warn(error)
+        self.ui.status(_("pushing keys completed\n"))
+
+    def pullkeys(self, remote):
+        """helper function to be called from pull()"""
+        rsp = {}
+        keys = remote.listkeys(keyhandlers.keys())
+        count = 0
+        for ns, values in keys.iteritems():
+            if ns in keyhandlers and keyhandlers[ns][1]:
+                count += len(values)
+                rsp[ns] = keyhandlers[ns][1](self, values)
+        for ns, error in rsp.iteritems():
+            if error:
+                self.ui.warn(error)
+        self.ui.status(_("added %d keys\n" % count))
+
     def changegroupinfo(self, nodes, source):
         if self.ui.verbose or source == 'bundle':
             self.ui.status(_("%d changesets found\n") % len(nodes))
diff --git a/mercurial/sshrepo.py b/mercurial/sshrepo.py
--- a/mercurial/sshrepo.py
+++ b/mercurial/sshrepo.py
@@ -8,7 +8,7 @@
 from node import bin, hex
 from i18n import _
 import repo, util, error, encoding
-import re, urllib
+import re, urllib, json
 
 class remotelock(object):
     def __init__(self, repo):
@@ -266,4 +266,13 @@
     def stream_out(self):
         return self.do_cmd('stream_out')
 
+    def listkeys(self, namespaces=None):
+        self.ui.status("listkeys")
+        return json.loads(self.call('listkeys',
+            namespaces=json.dumps(namespaces)), ensure_ascii=True)
+
+    def pushkeys(self, data):
+        return json.loads(self.call('pushkeys', data=json.loads(data)),
+                ensure_ascii=True)
+
 instance = sshrepository
diff --git a/mercurial/sshserver.py b/mercurial/sshserver.py
--- a/mercurial/sshserver.py
+++ b/mercurial/sshserver.py
@@ -9,11 +9,11 @@
 from i18n import _
 from node import bin, hex
 import streamclone, util, hook
-import os, sys, tempfile, urllib, copy
+import os, sys, tempfile, urllib, copy, json
 
 class sshserver(object):
 
-    caps = 'unbundle lookup changegroupsubset branchmap'.split()
+    caps = 'unbundle lookup changegroupsubset branchmap pushkeys'.split()
 
     def __init__(self, ui, repo):
         self.ui = ui
@@ -223,3 +223,7 @@
         except streamclone.StreamException, inst:
             self.fout.write(str(inst))
             self.fout.flush()
+
+    def do_listkeys(self):
+        namespaces = json.loads(self.getarg()[0].split())
+        return json.dumps(self.repo.listkeys(namespaces), ensure_ascii=True)