diff --git a/misc/sim/run-sim b/misc/sim/run-sim
index 985fe2f..abe108c 100755
--- a/misc/sim/run-sim
+++ b/misc/sim/run-sim
@@ -1,4 +1,4 @@
 #!/bin/bash
 export GOPATH=$PWD
 go get -d yggdrasil
-go run -tags debug misc/sim/treesim.go
+go run -tags debug misc/sim/treesim.go "$@"
diff --git a/misc/sim/treesim.go b/misc/sim/treesim.go
index 3a0959e..8a4bb2a 100644
--- a/misc/sim/treesim.go
+++ b/misc/sim/treesim.go
@@ -8,6 +8,7 @@ import "strconv"
 import "time"
 import "log"
 
+import "runtime"
 import "runtime/pprof"
 import "flag"
 
@@ -280,17 +281,7 @@ func pingNodes(store map[[32]byte]*Node) {
 			}
 			destAddr := dest.core.DEBUG_getAddr()[:]
 			ticker := time.NewTicker(150 * time.Millisecond)
-			ch := make(chan bool, 1)
-			ch <- true
-			doTicker := func() {
-				for range ticker.C {
-					select {
-					case ch <- true:
-					default:
-					}
-				}
-			}
-			go doTicker()
+			sendTo(payload, destAddr)
 			for loop := true; loop; {
 				select {
 				case packet := <-dest.recv:
@@ -299,7 +290,7 @@ func pingNodes(store map[[32]byte]*Node) {
 							loop = false
 						}
 					}
-				case <-ch:
+				case <-ticker.C:
 					sendTo(payload, destAddr)
 					//dumpDHTSize(store) // note that this uses racey functions to read things...
 				}
@@ -458,4 +449,5 @@ func main() {
 		var block chan struct{}
 		<-block
 	}
+	runtime.GC()
 }
diff --git a/src/yggdrasil/core.go b/src/yggdrasil/core.go
index 2f60a1b..9b9bcc1 100644
--- a/src/yggdrasil/core.go
+++ b/src/yggdrasil/core.go
@@ -22,7 +22,6 @@ type Core struct {
 	sigPriv     sigPrivKey
 	switchTable switchTable
 	peers       peers
-	sigs        sigManager
 	sessions    sessions
 	router      router
 	dht         dht
@@ -50,7 +49,6 @@ func (c *Core) init(bpub *boxPubKey,
 	c.boxPub, c.boxPriv = *bpub, *bpriv
 	c.sigPub, c.sigPriv = *spub, *spriv
 	c.admin.core = c
-	c.sigs.init()
 	c.searches.init(c)
 	c.dht.init(c)
 	c.sessions.init(c)
diff --git a/src/yggdrasil/dht.go b/src/yggdrasil/dht.go
index 31acd8a..e7815b7 100644
--- a/src/yggdrasil/dht.go
+++ b/src/yggdrasil/dht.go
@@ -273,6 +273,20 @@ func (t *dht) ping(info *dhtInfo, target *NodeID) {
 // Periodic maintenance work to keep important DHT nodes alive.
 func (t *dht) doMaintenance() {
 	now := time.Now()
+	newReqs := make(map[boxPubKey]map[NodeID]time.Time, len(t.reqs))
+	for key, dests := range t.reqs {
+		newDests := make(map[NodeID]time.Time, len(dests))
+		for nodeID, start := range dests {
+			if now.Sub(start) > 6*time.Second {
+				continue
+			}
+			newDests[nodeID] = start
+		}
+		if len(newDests) > 0 {
+			newReqs[key] = newDests
+		}
+	}
+	t.reqs = newReqs
 	for infoID, info := range t.table {
 		if now.Sub(info.recv) > time.Minute || info.pings > 3 {
 			delete(t.table, infoID)
diff --git a/src/yggdrasil/peer.go b/src/yggdrasil/peer.go
index cf82792..67aa805 100644
--- a/src/yggdrasil/peer.go
+++ b/src/yggdrasil/peer.go
@@ -175,7 +175,6 @@ func (p *peer) doSendSwitchMsgs() {
 // This must be launched in a separate goroutine by whatever sets up the peer struct.
 // It handles link protocol traffic.
 func (p *peer) linkLoop() {
-	go p.doSendSwitchMsgs()
 	tick := time.NewTicker(time.Second)
 	defer tick.Stop()
 	for {
@@ -317,7 +316,7 @@ func (p *peer) handleSwitchMsg(packet []byte) {
 		sigMsg.Hops = msg.Hops[:idx]
 		loc.coords = append(loc.coords, hop.Port)
 		bs := getBytesForSig(&hop.Next, &sigMsg)
-		if !p.core.sigs.check(&prevKey, &hop.Sig, bs) {
+		if !verify(&prevKey, bs, &hop.Sig) {
 			p.core.peers.removePeer(p.port)
 		}
 		prevKey = hop.Next
diff --git a/src/yggdrasil/router.go b/src/yggdrasil/router.go
index 41e2863..b482476 100644
--- a/src/yggdrasil/router.go
+++ b/src/yggdrasil/router.go
@@ -121,7 +121,6 @@ func (r *router) mainLoop() {
 				r.core.switchTable.doMaintenance()
 				r.core.dht.doMaintenance()
 				r.core.sessions.cleanup()
-				r.core.sigs.cleanup()
 				util_getBytes() // To slowly drain things
 			}
 		case f := <-r.admin:
diff --git a/src/yggdrasil/session.go b/src/yggdrasil/session.go
index b0022d7..92ae262 100644
--- a/src/yggdrasil/session.go
+++ b/src/yggdrasil/session.go
@@ -311,6 +311,11 @@ func (ss *sessions) createSession(theirPermKey *boxPubKey) *sessionInfo {
 
 func (ss *sessions) cleanup() {
 	// Time thresholds almost certainly could use some adjusting
+	for k := range ss.permShared {
+		// Delete a key, to make sure this eventually shrinks to 0
+		delete(ss.permShared, k)
+		break
+	}
 	if time.Since(ss.lastCleanup) < time.Minute {
 		return
 	}
@@ -319,6 +324,36 @@ func (ss *sessions) cleanup() {
 			s.close()
 		}
 	}
+	permShared := make(map[boxPubKey]*boxSharedKey, len(ss.permShared))
+	for k, v := range ss.permShared {
+		permShared[k] = v
+	}
+	ss.permShared = permShared
+	sinfos := make(map[handle]*sessionInfo, len(ss.sinfos))
+	for k, v := range ss.sinfos {
+		sinfos[k] = v
+	}
+	ss.sinfos = sinfos
+	byMySes := make(map[boxPubKey]*handle, len(ss.byMySes))
+	for k, v := range ss.byMySes {
+		byMySes[k] = v
+	}
+	ss.byMySes = byMySes
+	byTheirPerm := make(map[boxPubKey]*handle, len(ss.byTheirPerm))
+	for k, v := range ss.byTheirPerm {
+		byTheirPerm[k] = v
+	}
+	ss.byTheirPerm = byTheirPerm
+	addrToPerm := make(map[address]*boxPubKey, len(ss.addrToPerm))
+	for k, v := range ss.addrToPerm {
+		addrToPerm[k] = v
+	}
+	ss.addrToPerm = addrToPerm
+	subnetToPerm := make(map[subnet]*boxPubKey, len(ss.subnetToPerm))
+	for k, v := range ss.subnetToPerm {
+		subnetToPerm[k] = v
+	}
+	ss.subnetToPerm = subnetToPerm
 	ss.lastCleanup = time.Now()
 }
 
diff --git a/src/yggdrasil/signature.go b/src/yggdrasil/signature.go
deleted file mode 100644
index 203c9ad..0000000
--- a/src/yggdrasil/signature.go
+++ /dev/null
@@ -1,90 +0,0 @@
-package yggdrasil
-
-// This is where we record which signatures we've previously checked
-// It's so we can avoid needlessly checking them again
-
-import (
-	"sync"
-	"time"
-)
-
-// This keeps track of what signatures have already been checked.
-// It's used to skip expensive crypto operations, given that many signatures are likely to be the same for the average node's peers.
-type sigManager struct {
-	mutex       sync.RWMutex
-	checked     map[sigBytes]knownSig
-	lastCleaned time.Time
-}
-
-// Represents a known signature.
-// Includes the key, the signature bytes, the bytes that were signed, and the time it was last used.
-type knownSig struct {
-	key  sigPubKey
-	sig  sigBytes
-	bs   []byte
-	time time.Time
-}
-
-// Initializes the signature manager.
-func (m *sigManager) init() {
-	m.checked = make(map[sigBytes]knownSig)
-}
-
-// Checks if a key and signature match the supplied bytes.
-// If the same key/sig/bytes have been checked before, it returns true from the cached results.
-// If not, it checks the key, updates it in the cache if successful, and returns the checked results.
-func (m *sigManager) check(key *sigPubKey, sig *sigBytes, bs []byte) bool {
-	if m.isChecked(key, sig, bs) {
-		return true
-	}
-	verified := verify(key, bs, sig)
-	if verified {
-		m.putChecked(key, sig, bs)
-	}
-	return verified
-}
-
-// Checks the cache to see if this key/sig/bytes combination has already been verified.
-// Returns true if it finds a match.
-func (m *sigManager) isChecked(key *sigPubKey, sig *sigBytes, bs []byte) bool {
-	m.mutex.RLock()
-	defer m.mutex.RUnlock()
-	k, isIn := m.checked[*sig]
-	if !isIn {
-		return false
-	}
-	if k.key != *key || k.sig != *sig || len(bs) != len(k.bs) {
-		return false
-	}
-	for idx := 0; idx < len(bs); idx++ {
-		if bs[idx] != k.bs[idx] {
-			return false
-		}
-	}
-	k.time = time.Now()
-	return true
-}
-
-// Puts a new result into the cache.
-// This result is then used by isChecked to skip the expensive crypto verification if it's needed again.
-// This is useful because, for nodes with multiple peers, there is often a lot of overlap between the signatures provided by each peer.
-func (m *sigManager) putChecked(key *sigPubKey, newsig *sigBytes, bs []byte) {
-	m.mutex.Lock()
-	defer m.mutex.Unlock()
-	k := knownSig{key: *key, sig: *newsig, bs: bs, time: time.Now()}
-	m.checked[*newsig] = k
-}
-
-func (m *sigManager) cleanup() {
-	m.mutex.Lock()
-	defer m.mutex.Unlock()
-	if time.Since(m.lastCleaned) < time.Minute {
-		return
-	}
-	for s, k := range m.checked {
-		if time.Since(k.time) > time.Minute {
-			delete(m.checked, s)
-		}
-	}
-	m.lastCleaned = time.Now()
-}