diff --git a/src/twc-utils.c b/src/twc-utils.c
index 3f995ce..2ab5fac 100644
--- a/src/twc-utils.c
+++ b/src/twc-utils.c
@@ -168,3 +168,18 @@ twc_uint32_reverse_bytes(uint32_t num)
 
     return res;
 }
+
+/**
+ * Hash a Tox ID of size TOX_CLIENT_ID_SIZE bytes using a modified djb2 hash.
+ */
+unsigned long long
+twc_hash_tox_id(const uint8_t *tox_id)
+{
+    unsigned long long hash = 5381;
+
+    for (size_t i = 0; i < TOX_CLIENT_ID_SIZE; ++i)
+        hash ^= (hash << 5) + (hash >> 2) + tox_id[i];
+
+    return hash;
+}
+
diff --git a/src/twc-utils.h b/src/twc-utils.h
index 56e975f..45f5808 100644
--- a/src/twc-utils.h
+++ b/src/twc-utils.h
@@ -51,5 +51,8 @@ twc_get_friend_id_short(Tox *tox, int32_t friend_number);
 uint32_t
 twc_uint32_reverse_bytes(uint32_t num);
 
+unsigned long long
+twc_hash_tox_id(const uint8_t *tox_id);
+
 #endif // TOX_WEECHAT_UTILS_H