diff --git a/subscriber_list.go b/subscriber_list.go
index 115114cb..516b0d38 100644
--- a/subscriber_list.go
+++ b/subscriber_list.go
@@ -1,7 +1,7 @@
 package mercure
 
 import (
-	"encoding/base64"
+	"encoding/ascii85"
 	"sort"
 	"strings"
 
@@ -17,15 +17,10 @@ func NewSubscriberList(size int) *SubscriberList {
 		skipfilter: skipfilter.New(func(s interface{}, filter interface{}) bool {
 			var private bool
 
-			encodedTopics := strings.Split(filter.(string), ":")
+			encodedTopics := strings.Split(filter.(string), "~")
 			topics := make([]string, len(encodedTopics))
 			for i, encodedTopic := range encodedTopics {
-				decoded, err := base64.StdEncoding.DecodeString(encodedTopic)
-				if err != nil {
-					return false
-				}
-
-				p := strings.SplitN(string(decoded), "_", 2)
+				p := strings.SplitN(encodedTopic, ">", 2)
 				if len(p) < 2 {
 					return false
 				}
@@ -33,7 +28,16 @@ func NewSubscriberList(size int) *SubscriberList {
 				if p[0] == "p" {
 					private = true
 				}
-				topics[i] = p[1]
+
+				decodedTopic := make([]byte, len(p[1]))
+				ndst, _, err := ascii85.Decode(decodedTopic, []byte(p[1]), true)
+				if err != nil {
+					return false
+				}
+
+				str := string(decodedTopic[:ndst])
+
+				topics[i] = str
 			}
 
 			return s.(*Subscriber).MatchTopics(topics, private)
@@ -44,16 +48,20 @@ func NewSubscriberList(size int) *SubscriberList {
 func (sc *SubscriberList) MatchAny(u *Update) (res []*Subscriber) {
 	encodedTopics := make([]string, len(u.Topics))
 	for i, t := range u.Topics {
+		encodedTopic := make([]byte, ascii85.MaxEncodedLen(len(t)))
+		nb := ascii85.Encode(encodedTopic, []byte(t))
+		encodedTopic = encodedTopic[:nb]
+
 		if u.Private {
-			encodedTopics[i] = base64.StdEncoding.EncodeToString([]byte("p_" + t))
+			encodedTopics[i] = "p>" + string(encodedTopic)
 		} else {
-			encodedTopics[i] = base64.StdEncoding.EncodeToString([]byte("_" + t))
+			encodedTopics[i] = ">" + string(encodedTopic)
 		}
 	}
 
 	sort.Strings(encodedTopics)
 
-	for _, m := range sc.skipfilter.MatchAny(strings.Join(encodedTopics, ":")) {
+	for _, m := range sc.skipfilter.MatchAny(strings.Join(encodedTopics, "~")) {
 		res = append(res, m.(*Subscriber))
 	}