diff --git a/makefile b/makefile
index 0c94d89..61a883a 100644
--- a/makefile
+++ b/makefile
@@ -6,7 +6,7 @@
 SRC = src/grammar/types.c $(BUILDPATH)/$(GRAMMAR)/expenses.yy.c $(BUILDPATH)/$(GRAMMAR)/expenses.tab.c src/bot/handlers.c src/bot/context.c src/main.c
 INSTALLPATH = /usr/local
 CFLAGS = `pkg-config --cflags glib-2.0`
-LFLAGS =  -lstrophe `pkg-config --libs glib-2.0` 
+LFLAGS =  -lstrophe -lssl -lcrypto `pkg-config --libs glib-2.0` 
 DEBFLAGS = -g -Wall
 OFLAGS = -O2
 NAME = xmpp-bot
diff --git a/src/bot/context.c b/src/bot/context.c
index 014380a..220f5c7 100644
--- a/src/bot/context.c
+++ b/src/bot/context.c
@@ -10,10 +10,65 @@
     g_string_free(user.pass, freeSegment);
 }
 
-int bot_xmpp_set_avatar(struct BotXmppCtx * const bctx, const GString *avatarFile)
+/* Implement https://xmpp.org/extensions/xep-0084.html */
+/* TODO need to understand the format for data stanza encoding (bytes? base64?) */
+/* int bot_xmpp_set_avatar_user(struct BotXmppCtx * const bctx, const GString *avatarFile) */
+/* { */
+/*     gchar *avatar; */
+/*     gsize avatarLenght; */
+/*     xmpp_stanza_t *iq, *pubsub, *publish, *item, *data; */
+
+/*     /\* 1. Create IQ 'set' stanza *\/ */
+/*     iq = xmpp_stanza_new(bctx->ctx); */
+/*     xmpp_stanza_set_name(iq, "iq"); */
+/*     xmpp_stanza_set_type(iq, "set"); */
+/*     xmpp_stanza_set_id(iq, "publish1"); */
+
+/*     /\* Create <pubsub> protocol element*\/ */
+/*     pubsub = xmpp_stanza_new(bctx->ctx); */
+/*     xmpp_stanza_set_name(pubsub, "pubsub"); */
+/*     xmpp_stanza_set_ns(pubsub, "http://jabber.org/protocol/pubsub"); */
+/*     xmpp_stanza_add_child(iq, pubsub); */
+
+/*     /\* Create <publish> element *\/ */
+/*     publish = xmpp_stanza_new(bctx->ctx); */
+/*     xmpp_stanza_set_name(publish, "publish"); */
+/*     xmpp_stanza_set_attribute(publish, "node", "urn:xmpp:avatar:data"); */
+/*     xmpp_stanza_add_child(pubsub, publish); */
+
+/*     /\* Add <item> where id should be the sha1sum of the image *\/ */
+/*     item = xmpp_stanza_new(bctx->ctx); */
+/*     xmpp_stanza_set_name(item, "item"); */
+/* 	xmpp_stanza_set_id(item, "SHA1SUM"); */
+/*     xmpp_stanza_add_child(publish, item); */
+
+/*     /\* Add <data> with base64 data *\/ */
+/*     data = xmpp_stanza_new(bctx->ctx); */
+/*     xmpp_stanza_set_name(data, "data"); */
+/*     xmpp_stanza_set_ns(data, "urn:xmpp:avatar:data"); */
+/*     if(g_file_get_contents(avatarFile->str, &avatar, &avatarLenght, NULL)) { */
+/*         xmpp_stanza_set_text(data, avatar); */
+/*     } else { */
+/*         fprintf(stderr, "Unable to read png avatar.\n"); */
+/*     } */
+/*     xmpp_stanza_set_text(data, "DATA"); */
+/*     xmpp_stanza_add_child(item, data); */
+
+/*     /\* 6. Send stanza and release it + all children *\/ */
+/*     xmpp_send(bctx->conn, iq); */
+/*     xmpp_stanza_release(iq); */
+
+/*     return 0; */
+/* } */
+
+
+/* implement https://xmpp.org/extensions/xep-0153.html */
+GString *bot_xmpp_set_avatar(struct BotXmppCtx * const bctx, const GString *avatarFile)
 {
     gchar *avatar;
     gsize avatarLenght;
+    GString *avatarID;
+    unsigned char hash[SHA_DIGEST_LENGTH]; /* == 20 */
     xmpp_stanza_t *iq, *vcard, *photo, *type, *binval;
 
     /* 1. Create IQ 'set' stanza */
@@ -26,10 +81,12 @@
     vcard = xmpp_stanza_new(bctx->ctx);
     xmpp_stanza_set_name(vcard, "vCard");
     xmpp_stanza_set_ns(vcard, "vcard-temp");
+    xmpp_stanza_add_child(iq, vcard);
 
     /* Create <PHOTO> element */
     photo = xmpp_stanza_new(bctx->ctx);
     xmpp_stanza_set_name(photo, "PHOTO");
+    xmpp_stanza_add_child(vcard, photo);
 
     /* Add <TYPE> (e.g., image/jpeg) */
     type = xmpp_stanza_new(bctx->ctx);
@@ -42,22 +99,18 @@
     xmpp_stanza_set_name(binval, "BINVAL");
 
     if(g_file_get_contents(avatarFile->str, &avatar, &avatarLenght, NULL)) {
+        SHA1(avatarFile->str, sizeof(avatarFile->str)-1, hash);
         xmpp_stanza_set_text(binval, avatar);
     } else {
         fprintf(stderr, "Unable to read BASE64-encoded avatar.\n");
     }
-
     xmpp_stanza_add_child(photo, binval);
 
-    /* Assemble tree */
-    xmpp_stanza_add_child(vcard, photo);
-    xmpp_stanza_add_child(iq, vcard);
-
     /* 6. Send stanza and release it + all children */
     xmpp_send(bctx->conn, iq);
     xmpp_stanza_release(iq);
 
-    return 0;
+    return g_string_new(hash);
 }
 
 int bot_xmpp_startup(struct BotUserInfo user, GString *avatarFile, struct BotXmppCtx * const bctx)
@@ -65,6 +118,7 @@
     xmpp_log_t* newLog;
     xmpp_ctx_t* newCtx;
     xmpp_conn_t* newCon;
+    GString *avatarID;
     int connectStatus;
 
     /* init library */
@@ -91,6 +145,9 @@
     xmpp_conn_set_jid(newCon, user.jid->str);
     xmpp_conn_set_pass(newCon, user.pass->str);
 
+    /* TODO properly set avatarID in presence stanza */
+    avatarID = bot_xmpp_set_avatar(bctx, avatarFile);
+
     /* initiate connection */
     connectStatus = xmpp_connect_client(newCon, NULL, 0, conn_handler, newCtx);
     if(connectStatus != 0) {
@@ -102,8 +159,6 @@
     (*bctx).ctx = newCtx;
     (*bctx).conn = newCon;
 
-    bot_xmpp_set_avatar(bctx, avatarFile);
-
     return 0;
 }
 
diff --git a/src/bot/context.h b/src/bot/context.h
index 2c0fbc1..8a49dc2 100644
--- a/src/bot/context.h
+++ b/src/bot/context.h
@@ -12,6 +12,7 @@
 #include <stdbool.h>
 #include <glib.h>
 #include <strophe.h>
+#include <openssl/sha.h> /* For SHA1 */
 #include "handlers.h"
 
 struct BotUserInfo {
@@ -28,7 +29,7 @@
 void bot_free_user_data(struct BotUserInfo user, GString *filename, bool freeSegment);
 
 /* sets the given avatar file (base64 encoded) */
-int bot_xmpp_set_avatar(struct BotXmppCtx * const bctx, const GString *avatarFile);
+GString *bot_xmpp_set_avatar(struct BotXmppCtx * const bctx, const GString *avatarFile);
 
 /* perform xmpp startup, store in bctx if completed successfully */
 int bot_xmpp_startup(struct BotUserInfo user, GString *avatarFile, struct BotXmppCtx * const bctx);