diff --git a/openair3/NAS/COMMON/EMM/MSG/AttachRequest.c b/openair3/NAS/COMMON/EMM/MSG/AttachRequest.c
index 7448a33419..8edac423c3 100644
--- a/openair3/NAS/COMMON/EMM/MSG/AttachRequest.c
+++ b/openair3/NAS/COMMON/EMM/MSG/AttachRequest.c
@@ -47,7 +47,7 @@ int decode_attach_request(attach_request_msg *attach_request, uint8_t *buffer, u
     LOG_FUNC_RETURN(decoded_result);
   }
 
-  if ((decoded_result = decode_u8_nas_key_set_identifier(&attach_request->naskeysetidentifier, 0, *(buffer + decoded) >> 4, len - decoded)) < 0) {
+  if ((decoded_result = decode_nas_key_set_identifier(&attach_request->naskeysetidentifier, 0, *(buffer + decoded) >> 4)) < 0) {
     //         return decoded_result;
     LOG_FUNC_RETURN(decoded_result);
   }
@@ -299,7 +299,8 @@ int encode_attach_request(attach_request_msg *attach_request, uint8_t *buffer, u
   /* Checking IEI and pointer */
   CHECK_PDU_POINTER_AND_LENGTH_ENCODER(buffer, ATTACH_REQUEST_MINIMUM_LENGTH, len);
 
-  *(buffer + encoded) = ((encode_u8_nas_key_set_identifier(&attach_request->naskeysetidentifier) & 0x0f) << 4) | (encode_u8_eps_attach_type(&attach_request->epsattachtype) & 0x0f);
+  *(buffer + encoded) = ((encode_nas_key_set_identifier(&attach_request->naskeysetidentifier, 0) & 0x0f) << 4)
+                        | (encode_u8_eps_attach_type(&attach_request->epsattachtype) & 0x0f);
   encoded++;
 
   if ((encode_result =
diff --git a/openair3/NAS/COMMON/EMM/MSG/AuthenticationRequest.c b/openair3/NAS/COMMON/EMM/MSG/AuthenticationRequest.c
index 0914353478..71477f3aeb 100644
--- a/openair3/NAS/COMMON/EMM/MSG/AuthenticationRequest.c
+++ b/openair3/NAS/COMMON/EMM/MSG/AuthenticationRequest.c
@@ -38,7 +38,8 @@ int decode_authentication_request(authentication_request_msg *authentication_req
   CHECK_PDU_POINTER_AND_LENGTH_DECODER(buffer, AUTHENTICATION_REQUEST_MINIMUM_LENGTH, len);
 
   /* Decoding mandatory fields */
-  if ((decoded_result = decode_u8_nas_key_set_identifier(&authentication_request->naskeysetidentifierasme, 0, *(buffer + decoded), len - decoded)) < 0)
+  if ((decoded_result = decode_nas_key_set_identifier(&authentication_request->naskeysetidentifierasme, 0, *(buffer + decoded)))
+      < 0)
     return decoded_result;
 
   decoded++;
@@ -64,7 +65,7 @@ int encode_authentication_request(authentication_request_msg *authentication_req
   /* Checking IEI and pointer */
   CHECK_PDU_POINTER_AND_LENGTH_ENCODER(buffer, AUTHENTICATION_REQUEST_MINIMUM_LENGTH, len);
 
-  *(buffer + encoded) = ((encode_u8_nas_key_set_identifier(&authentication_request->naskeysetidentifierasme) & 0x0f) << 4) | 0x00;
+  *(buffer + encoded) = ((encode_nas_key_set_identifier(&authentication_request->naskeysetidentifierasme, 0) & 0x0f) << 4) | 0x00;
   encoded++;
 
   if ((encode_result =
diff --git a/openair3/NAS/COMMON/EMM/MSG/DetachRequest.c b/openair3/NAS/COMMON/EMM/MSG/DetachRequest.c
index 1697ea17e2..8a63ea71c8 100644
--- a/openair3/NAS/COMMON/EMM/MSG/DetachRequest.c
+++ b/openair3/NAS/COMMON/EMM/MSG/DetachRequest.c
@@ -41,7 +41,7 @@ int decode_detach_request(detach_request_msg *detach_request, uint8_t *buffer, u
   if ((decoded_result = decode_u8_detach_type(&detach_request->detachtype, 0, *(buffer + decoded) & 0x0f, len - decoded)) < 0)
     return decoded_result;
 
-  if ((decoded_result = decode_u8_nas_key_set_identifier(&detach_request->naskeysetidentifier, 0, *(buffer + decoded) >> 4, len - decoded)) < 0)
+  if ((decoded_result = decode_nas_key_set_identifier(&detach_request->naskeysetidentifier, 0, *(buffer + decoded) >> 4)) < 0)
     return decoded_result;
 
   decoded++;
@@ -62,7 +62,8 @@ int encode_detach_request(detach_request_msg *detach_request, uint8_t *buffer, u
   /* Checking IEI and pointer */
   CHECK_PDU_POINTER_AND_LENGTH_ENCODER(buffer, DETACH_REQUEST_MINIMUM_LENGTH, len);
 
-  *(buffer + encoded) = ((encode_u8_nas_key_set_identifier(&detach_request->naskeysetidentifier) << 4) | (encode_u8_detach_type(&detach_request->detachtype) & 0x0f));
+  *(buffer + encoded) = ((encode_nas_key_set_identifier(&detach_request->naskeysetidentifier, 0) << 4)
+                         | (encode_u8_detach_type(&detach_request->detachtype) & 0x0f));
   encoded++;
 
   if ((encode_result = encode_eps_mobile_identity(&detach_request->gutiorimsi,
diff --git a/openair3/NAS/COMMON/EMM/MSG/ExtendedServiceRequest.c b/openair3/NAS/COMMON/EMM/MSG/ExtendedServiceRequest.c
index a7ff89245b..99a556c7f3 100644
--- a/openair3/NAS/COMMON/EMM/MSG/ExtendedServiceRequest.c
+++ b/openair3/NAS/COMMON/EMM/MSG/ExtendedServiceRequest.c
@@ -41,7 +41,9 @@ int decode_extended_service_request(extended_service_request_msg *extended_servi
   if ((decoded_result = decode_u8_service_type(&extended_service_request->servicetype, 0, *(buffer + decoded) >> 4, len - decoded)) < 0)
     return decoded_result;
 
-  if ((decoded_result = decode_u8_nas_key_set_identifier(&extended_service_request->naskeysetidentifier, 0, *(buffer + decoded) & 0x0f, len - decoded)) < 0)
+  if ((decoded_result =
+           decode_nas_key_set_identifier(&extended_service_request->naskeysetidentifier, 0, *(buffer + decoded) & 0x0f))
+      < 0)
     return decoded_result;
 
   decoded++;
@@ -62,7 +64,8 @@ int encode_extended_service_request(extended_service_request_msg *extended_servi
   /* Checking IEI and pointer */
   CHECK_PDU_POINTER_AND_LENGTH_ENCODER(buffer, EXTENDED_SERVICE_REQUEST_MINIMUM_LENGTH, len);
 
-  *(buffer + encoded) = ((encode_u8_service_type(&extended_service_request->servicetype) & 0x0f) << 4) | (encode_u8_nas_key_set_identifier(&extended_service_request->naskeysetidentifier) & 0x0f);
+  *(buffer + encoded) = ((encode_u8_service_type(&extended_service_request->servicetype) & 0x0f) << 4)
+                        | (encode_nas_key_set_identifier(&extended_service_request->naskeysetidentifier, 0) & 0x0f);
   encoded++;
 
   if ((encode_result =
diff --git a/openair3/NAS/COMMON/EMM/MSG/FGSDeregistrationRequestUEOriginating.c b/openair3/NAS/COMMON/EMM/MSG/FGSDeregistrationRequestUEOriginating.c
index 0d9a4bbac2..af8dfd8c20 100644
--- a/openair3/NAS/COMMON/EMM/MSG/FGSDeregistrationRequestUEOriginating.c
+++ b/openair3/NAS/COMMON/EMM/MSG/FGSDeregistrationRequestUEOriginating.c
@@ -33,6 +33,7 @@
 #include <stdint.h>
 
 #include "FGSDeregistrationRequestUEOriginating.h"
+#include "NR_NAS_defs.h"
 
 int encode_fgs_deregistration_request_ue_originating(fgs_deregistration_request_ue_originating_msg *drr,
                                                      uint8_t *buffer,
@@ -45,7 +46,7 @@ int encode_fgs_deregistration_request_ue_originating(fgs_deregistration_request_
                       | ((dt->access_type & 0x3) << 4);
 
   int encode_result;
-  if ((encode_result = encode_nas_key_set_identifier(&drr->naskeysetidentifier, 0, buffer + encoded, len - encoded)) < 0)
+  if ((encode_result = encode_nas_key_set_identifier(&drr->naskeysetidentifier, IEI_NULL)) < 0)
     return encode_result;
 
   encoded++;
diff --git a/openair3/NAS/COMMON/EMM/MSG/RegistrationRequest.c b/openair3/NAS/COMMON/EMM/MSG/RegistrationRequest.c
index 3d177c396a..cf18e46ca2 100644
--- a/openair3/NAS/COMMON/EMM/MSG/RegistrationRequest.c
+++ b/openair3/NAS/COMMON/EMM/MSG/RegistrationRequest.c
@@ -35,6 +35,7 @@
 #include "nas_log.h"
 
 #include "RegistrationRequest.h"
+#include "NR_NAS_defs.h"
 
 int decode_registration_request(registration_request_msg *registration_request, uint8_t *buffer, uint32_t len)
 {
@@ -51,7 +52,8 @@ int decode_registration_request(registration_request_msg *registration_request,
     LOG_FUNC_RETURN(decoded_result);
   }
 
-  if ((decoded_result = decode_u8_nas_key_set_identifier(&registration_request->naskeysetidentifier, 0, *(buffer + decoded) >> 4, len - decoded)) < 0) {
+  if ((decoded_result = decode_nas_key_set_identifier(&registration_request->naskeysetidentifier, IEI_NULL, *(buffer + decoded) >> 4))
+      < 0) {
     //         return decoded_result;
     LOG_FUNC_RETURN(decoded_result);
   }
@@ -75,7 +77,8 @@ int encode_registration_request(registration_request_msg *registration_request,
   int encoded = 0;
   int encode_result = 0;
 
-  *(buffer + encoded) = ((encode_u8_nas_key_set_identifier(&registration_request->naskeysetidentifier) & 0x0f) << 4) | (encode_5gs_registration_type(&registration_request->fgsregistrationtype) & 0x0f);
+  *(buffer + encoded) = ((encode_nas_key_set_identifier(&registration_request->naskeysetidentifier, IEI_NULL) & 0x0f) << 4)
+                        | (encode_5gs_registration_type(&registration_request->fgsregistrationtype) & 0x0f);
   encoded++;
 
   if ((encode_result =
diff --git a/openair3/NAS/COMMON/EMM/MSG/SecurityModeCommand.c b/openair3/NAS/COMMON/EMM/MSG/SecurityModeCommand.c
index 25181d8e79..2e936e6a94 100644
--- a/openair3/NAS/COMMON/EMM/MSG/SecurityModeCommand.c
+++ b/openair3/NAS/COMMON/EMM/MSG/SecurityModeCommand.c
@@ -43,7 +43,8 @@ int decode_security_mode_command(security_mode_command_msg *security_mode_comman
   else
     decoded += decoded_result;
 
-  if ((decoded_result = decode_u8_nas_key_set_identifier(&security_mode_command->naskeysetidentifier, 0, *(buffer + decoded) & 0x0f, len - decoded)) < 0)
+  if ((decoded_result = decode_nas_key_set_identifier(&security_mode_command->naskeysetidentifier, 0, *(buffer + decoded) & 0x0f))
+      < 0)
     return decoded_result;
 
   decoded++;
@@ -124,7 +125,7 @@ int encode_security_mode_command(security_mode_command_msg *security_mode_comman
   else
     encoded += encode_result;
 
-  *(buffer + encoded) = (encode_u8_nas_key_set_identifier(&security_mode_command->naskeysetidentifier) & 0x0f);
+  *(buffer + encoded) = (encode_nas_key_set_identifier(&security_mode_command->naskeysetidentifier, 0) & 0x0f);
   encoded++;
 
   if ((encode_result =
diff --git a/openair3/NAS/COMMON/EMM/MSG/TrackingAreaUpdateRequest.c b/openair3/NAS/COMMON/EMM/MSG/TrackingAreaUpdateRequest.c
index 49632057c0..83968bc2c6 100644
--- a/openair3/NAS/COMMON/EMM/MSG/TrackingAreaUpdateRequest.c
+++ b/openair3/NAS/COMMON/EMM/MSG/TrackingAreaUpdateRequest.c
@@ -41,7 +41,9 @@ int decode_tracking_area_update_request(tracking_area_update_request_msg *tracki
   if ((decoded_result = decode_u8_eps_update_type(&tracking_area_update_request->epsupdatetype, 0, *(buffer + decoded) >> 4, len - decoded)) < 0)
     return decoded_result;
 
-  if ((decoded_result = decode_u8_nas_key_set_identifier(&tracking_area_update_request->naskeysetidentifier, 0, *(buffer + decoded) & 0x0f, len - decoded)) < 0)
+  if ((decoded_result =
+           decode_nas_key_set_identifier(&tracking_area_update_request->naskeysetidentifier, 0, *(buffer + decoded) & 0x0f))
+      < 0)
     return decoded_result;
 
   decoded++;
@@ -61,10 +63,10 @@ int decode_tracking_area_update_request(tracking_area_update_request_msg *tracki
 
     switch(ieiDecoded) {
     case TRACKING_AREA_UPDATE_REQUEST_NONCURRENT_NATIVE_NAS_KEY_SET_IDENTIFIER_IEI:
-      if ((decoded_result =
-             decode_nas_key_set_identifier(&tracking_area_update_request->noncurrentnativenaskeysetidentifier,
-                                           TRACKING_AREA_UPDATE_REQUEST_NONCURRENT_NATIVE_NAS_KEY_SET_IDENTIFIER_IEI,
-                                           buffer + decoded, len - decoded)) <= 0)
+      if ((decoded_result = decode_nas_key_set_identifier(&tracking_area_update_request->noncurrentnativenaskeysetidentifier,
+                                                          TRACKING_AREA_UPDATE_REQUEST_NONCURRENT_NATIVE_NAS_KEY_SET_IDENTIFIER_IEI,
+                                                          *(buffer + decoded)))
+          <= 0)
         return decoded_result;
 
       decoded += decoded_result;
@@ -293,8 +295,8 @@ int encode_tracking_area_update_request(tracking_area_update_request_msg *tracki
   /* Checking IEI and pointer */
   CHECK_PDU_POINTER_AND_LENGTH_ENCODER(buffer, TRACKING_AREA_UPDATE_REQUEST_MINIMUM_LENGTH, len);
 
-  *(buffer + encoded) = ((encode_u8_eps_update_type(&tracking_area_update_request->epsupdatetype) & 0x0f) << 4) | (encode_u8_nas_key_set_identifier(
-                          &tracking_area_update_request->naskeysetidentifier) & 0x0f);
+  *(buffer + encoded) = ((encode_u8_eps_update_type(&tracking_area_update_request->epsupdatetype) & 0x0f) << 4)
+                        | (encode_nas_key_set_identifier(&tracking_area_update_request->naskeysetidentifier, 0) & 0x0f);
   encoded++;
 
   if ((encode_result =
@@ -306,10 +308,9 @@ int encode_tracking_area_update_request(tracking_area_update_request_msg *tracki
 
   if ((tracking_area_update_request->presencemask & TRACKING_AREA_UPDATE_REQUEST_NONCURRENT_NATIVE_NAS_KEY_SET_IDENTIFIER_PRESENT)
       == TRACKING_AREA_UPDATE_REQUEST_NONCURRENT_NATIVE_NAS_KEY_SET_IDENTIFIER_PRESENT) {
-    if ((encode_result =
-           encode_nas_key_set_identifier(&tracking_area_update_request->noncurrentnativenaskeysetidentifier,
-                                         TRACKING_AREA_UPDATE_REQUEST_NONCURRENT_NATIVE_NAS_KEY_SET_IDENTIFIER_IEI,
-                                         buffer + encoded, len - encoded)) < 0)
+    if ((encode_result = encode_nas_key_set_identifier(&tracking_area_update_request->noncurrentnativenaskeysetidentifier,
+                                                       TRACKING_AREA_UPDATE_REQUEST_NONCURRENT_NATIVE_NAS_KEY_SET_IDENTIFIER_IEI))
+        < 0)
       // Return in case of error
       return encode_result;
     else
diff --git a/openair3/NAS/COMMON/IES/NasKeySetIdentifier.c b/openair3/NAS/COMMON/IES/NasKeySetIdentifier.c
index a547675675..82fe69d79e 100644
--- a/openair3/NAS/COMMON/IES/NasKeySetIdentifier.c
+++ b/openair3/NAS/COMMON/IES/NasKeySetIdentifier.c
@@ -28,67 +28,34 @@
 #include "TLVDecoder.h"
 #include "NasKeySetIdentifier.h"
 
-int decode_nas_key_set_identifier(NasKeySetIdentifier *naskeysetidentifier, uint8_t iei, uint8_t *buffer, uint32_t len)
+/**
+ * @brief Decode the NAS key set identifier from one byte
+ */
+int decode_nas_key_set_identifier(NasKeySetIdentifier *naskeysetidentifier, uint8_t iei, uint8_t value)
 {
-  int decoded = 0;
-  CHECK_PDU_POINTER_AND_LENGTH_DECODER(buffer, NAS_KEY_SET_IDENTIFIER_MINIMUM_LENGTH, len);
-
   if (iei > 0) {
-    CHECK_IEI_DECODER((*buffer & 0xf0), iei);
+    CHECK_IEI_DECODER((value & 0xf0), iei);
   }
 
-  naskeysetidentifier->tsc = (*(buffer + decoded) >> 3) & 0x1;
-  naskeysetidentifier->naskeysetidentifier = *(buffer + decoded) & 0x7;
-  decoded++;
+  naskeysetidentifier->tsc = (value >> 3) & 0x1;
+  naskeysetidentifier->naskeysetidentifier = value & 0x7;
+
+#if defined(NAS_DEBUG)
+  dump_nas_key_set_identifier_xml(naskeysetidentifier, iei);
+#endif
+
+  return 1; // 1 octet
+}
+
+/**
+ * @brief Encode the NAS key set identifier in one byte
+ */
+uint8_t encode_nas_key_set_identifier(NasKeySetIdentifier *naskeysetidentifier, uint8_t iei)
+{
 #if defined (NAS_DEBUG)
   dump_nas_key_set_identifier_xml(naskeysetidentifier, iei);
 #endif
-  return decoded;
-}
-
-int decode_u8_nas_key_set_identifier(NasKeySetIdentifier *naskeysetidentifier, uint8_t iei, uint8_t value, uint32_t len)
-{
-  int decoded = 0;
-  uint8_t *buffer = &value;
-  naskeysetidentifier->tsc = (*(buffer + decoded) >> 3) & 0x1;
-  naskeysetidentifier->naskeysetidentifier = *(buffer + decoded) & 0x7;
-  decoded++;
-#if defined (NAS_DEBUG)
-  dump_nas_key_set_identifier_xml(naskeysetidentifier, iei);
-#endif
-  return decoded;
-}
-
-int encode_nas_key_set_identifier(NasKeySetIdentifier *naskeysetidentifier, uint8_t iei, uint8_t *buffer, uint32_t len)
-{
-  uint8_t encoded = 0;
-  /* Checking length and pointer */
-  CHECK_PDU_POINTER_AND_LENGTH_ENCODER(buffer, NAS_KEY_SET_IDENTIFIER_MINIMUM_LENGTH, len);
-#if defined (NAS_DEBUG)
-  dump_nas_key_set_identifier_xml(naskeysetidentifier, iei);
-#endif
-  *(buffer + encoded) = 0x00 | (iei & 0xf0) |
-                        ((naskeysetidentifier->tsc & 0x1) << 3) |
-                        (naskeysetidentifier->naskeysetidentifier & 0x7);
-  encoded++;
-  return encoded;
-}
-
-uint8_t encode_u8_nas_key_set_identifier(NasKeySetIdentifier *naskeysetidentifier)
-{
-  uint8_t bufferReturn;
-  uint8_t *buffer = &bufferReturn;
-  uint8_t encoded = 0;
-  uint8_t iei = 0;
-#if defined (NAS_DEBUG)
-  dump_nas_key_set_identifier_xml(naskeysetidentifier, 0);
-#endif
-  *(buffer + encoded) = 0x00 | (iei & 0xf0) |
-                        ((naskeysetidentifier->tsc & 0x1) << 3) |
-                        (naskeysetidentifier->naskeysetidentifier & 0x7);
-  encoded++;
-
-  return bufferReturn;
+  return ((iei & 0xf0) | (naskeysetidentifier->tsc & 0x1) << 3) | (naskeysetidentifier->naskeysetidentifier & 0x7);
 }
 
 void dump_nas_key_set_identifier_xml(NasKeySetIdentifier *naskeysetidentifier, uint8_t iei)
diff --git a/openair3/NAS/COMMON/IES/NasKeySetIdentifier.h b/openair3/NAS/COMMON/IES/NasKeySetIdentifier.h
index 09daf13a56..5f6b445fc4 100644
--- a/openair3/NAS/COMMON/IES/NasKeySetIdentifier.h
+++ b/openair3/NAS/COMMON/IES/NasKeySetIdentifier.h
@@ -39,15 +39,11 @@ typedef struct NasKeySetIdentifier_tag {
   uint8_t  naskeysetidentifier:3;
 } NasKeySetIdentifier;
 
-int encode_nas_key_set_identifier(NasKeySetIdentifier *naskeysetidentifier, uint8_t iei, uint8_t *buffer, uint32_t len);
+uint8_t encode_nas_key_set_identifier(NasKeySetIdentifier *naskeysetidentifier, uint8_t iei);
 
 void dump_nas_key_set_identifier_xml(NasKeySetIdentifier *naskeysetidentifier, uint8_t iei);
 
-uint8_t encode_u8_nas_key_set_identifier(NasKeySetIdentifier *naskeysetidentifier);
-
-int decode_nas_key_set_identifier(NasKeySetIdentifier *naskeysetidentifier, uint8_t iei, uint8_t *buffer, uint32_t len);
-
-int decode_u8_nas_key_set_identifier(NasKeySetIdentifier *naskeysetidentifier, uint8_t iei, uint8_t value, uint32_t len);
+int decode_nas_key_set_identifier(NasKeySetIdentifier *naskeysetidentifier, uint8_t iei, uint8_t value);
 
 #endif /* NAS KEY SET IDENTIFIER_H_ */
 
diff --git a/openair3/NAS/COMMON/NR_NAS_defs.h b/openair3/NAS/COMMON/NR_NAS_defs.h
index 1ced950a4d..f5510e5392 100644
--- a/openair3/NAS/COMMON/NR_NAS_defs.h
+++ b/openair3/NAS/COMMON/NR_NAS_defs.h
@@ -256,6 +256,7 @@ typedef enum {
 } cause_secu_id_t;
 								
 // IEI (information element identifier) are spread in each message definition
+#define IEI_NULL 0x00
 #define IEI_RAND 0x21
 #define IEI_AUTN 0x20
 #define IEI_EAP  0x78