diff --git a/ble/central_device_db.h b/ble/central_device_db.h
index 6e25ac438..d882b0828 100644
--- a/ble/central_device_db.h
+++ b/ble/central_device_db.h
@@ -38,26 +38,73 @@
 
 #include <btstack/utils.h>
 
+/** 
+
+	A Central Device DB is only required for signed writes
+	
+	Per bonded device, it stores the Identity Resolving Key (IRK), the Connection Signature Resolving Key (CSRK)
+	   and the last used counter
+
+	The IRK is necessary to identify a device that uses private addresses
+	The CSRK is used to generate the signatur on the remote device and is needed to verify the signature itself
+	The Counter is necessary to prevent reply attacks
+
+*/
+
+
 // Central Device db interface
+
+
+/**
+ * @brief init
+ */
 void central_device_db_init();
 
-// @returns index if successful, -1 otherwise
+/**
+ * @brief add device to db
+ * @param addr_type, address of the device
+ * @param irk and csrk of the device
+ * @returns index if successful, -1 otherwise
+ */
 int central_device_db_add(int addr_type, bd_addr_t addr, sm_key_t irk, sm_key_t csrk);
 
-// @returns number of device in db
+/**
+ * @brief get number of devices in db for enumeration
+ * @returns number of device in db
+ */
 int central_device_db_count(void);
 
-// get device information: addr type and address
-void central_device_db_info(int index, int * addr_type, bd_addr_t addr, sm_key_t csrk);
+/**
+ * @brief get device information: addr type and address needed to identify device
+ * @param index
+ * @param addr_type, address of the device as output
+ * @param irk of the device
+ */
+void central_device_db_info(int index, int * addr_type, bd_addr_t addr, sm_key_t irk);
 
-// get signature key
+/**
+ * @brief get signing key for this device
+ * @param index
+ * @param signing key as output
+ */
 void central_device_db_csrk(int index, sm_key_t csrk);
 
-// query last used/seen signing counter
+/**
+ * @brief query last used/seen signing counter
+ * @param index
+ * @returns next expected counter, 0 after devices was added
+ */
 uint32_t central_device_db_counter_get(int index);
 
-// update signing counter
+/**
+ * @brief update signing counter
+ * @param index
+ * @param counter to store
+ */
 void central_device_db_counter_set(int index, uint32_t counter);
 
-// free device
-void central_device_db_remove(int index);
\ No newline at end of file
+/**
+ * @brief free device
+ * @param index
+ */
+void central_device_db_remove(int index);