diff --git a/openair3/NAS/COMMON/IES/AuthenticationResponseParameter.c b/openair3/NAS/COMMON/IES/AuthenticationResponseParameter.c
index 3ac3e60a3d..85bcaeb1b2 100644
--- a/openair3/NAS/COMMON/IES/AuthenticationResponseParameter.c
+++ b/openair3/NAS/COMMON/IES/AuthenticationResponseParameter.c
@@ -53,7 +53,10 @@ int decode_authentication_response_parameter(AuthenticationResponseParameter *au
 #endif
   return decoded;
 }
-int encode_authentication_response_parameter(AuthenticationResponseParameter *authenticationresponseparameter, uint8_t iei, uint8_t *buffer, uint32_t len)
+int encode_authentication_response_parameter(const AuthenticationResponseParameter *authenticationresponseparameter,
+                                             uint8_t iei,
+                                             uint8_t *buffer,
+                                             uint32_t len)
 {
   uint8_t *lenPtr;
   uint32_t encoded = 0;
diff --git a/openair3/NAS/COMMON/IES/AuthenticationResponseParameter.h b/openair3/NAS/COMMON/IES/AuthenticationResponseParameter.h
index 4e3dd33d5b..75a2dd9a2d 100644
--- a/openair3/NAS/COMMON/IES/AuthenticationResponseParameter.h
+++ b/openair3/NAS/COMMON/IES/AuthenticationResponseParameter.h
@@ -35,7 +35,10 @@ typedef struct AuthenticationResponseParameter_tag {
   OctetString res;
 } AuthenticationResponseParameter;
 
-int encode_authentication_response_parameter(AuthenticationResponseParameter *authenticationresponseparameter, uint8_t iei, uint8_t *buffer, uint32_t len);
+int encode_authentication_response_parameter(const AuthenticationResponseParameter *authenticationresponseparameter,
+                                             uint8_t iei,
+                                             uint8_t *buffer,
+                                             uint32_t len);
 
 int decode_authentication_response_parameter(AuthenticationResponseParameter *authenticationresponseparameter, uint8_t iei, uint8_t *buffer, uint32_t len);
 
diff --git a/openair3/NAS/COMMON/IES/NasKeySetIdentifier.c b/openair3/NAS/COMMON/IES/NasKeySetIdentifier.c
index 82fe69d79e..368e66911b 100644
--- a/openair3/NAS/COMMON/IES/NasKeySetIdentifier.c
+++ b/openair3/NAS/COMMON/IES/NasKeySetIdentifier.c
@@ -50,7 +50,7 @@ int decode_nas_key_set_identifier(NasKeySetIdentifier *naskeysetidentifier, uint
 /**
  * @brief Encode the NAS key set identifier in one byte
  */
-uint8_t encode_nas_key_set_identifier(NasKeySetIdentifier *naskeysetidentifier, uint8_t iei)
+uint8_t encode_nas_key_set_identifier(const NasKeySetIdentifier *naskeysetidentifier, uint8_t iei)
 {
 #if defined (NAS_DEBUG)
   dump_nas_key_set_identifier_xml(naskeysetidentifier, iei);
diff --git a/openair3/NAS/COMMON/IES/NasKeySetIdentifier.h b/openair3/NAS/COMMON/IES/NasKeySetIdentifier.h
index 5f6b445fc4..bdc1506cb2 100644
--- a/openair3/NAS/COMMON/IES/NasKeySetIdentifier.h
+++ b/openair3/NAS/COMMON/IES/NasKeySetIdentifier.h
@@ -39,7 +39,7 @@ typedef struct NasKeySetIdentifier_tag {
   uint8_t  naskeysetidentifier:3;
 } NasKeySetIdentifier;
 
-uint8_t encode_nas_key_set_identifier(NasKeySetIdentifier *naskeysetidentifier, uint8_t iei);
+uint8_t encode_nas_key_set_identifier(const NasKeySetIdentifier *naskeysetidentifier, uint8_t iei);
 
 void dump_nas_key_set_identifier_xml(NasKeySetIdentifier *naskeysetidentifier, uint8_t iei);
 
diff --git a/openair3/NAS/COMMON/UTIL/OctetString.c b/openair3/NAS/COMMON/UTIL/OctetString.c
index 2f1b7b2c32..4afa522664 100644
--- a/openair3/NAS/COMMON/UTIL/OctetString.c
+++ b/openair3/NAS/COMMON/UTIL/OctetString.c
@@ -55,8 +55,7 @@ void free_octet_string(OctetString *octetstring)
   }
 }
 
-
-int encode_octet_string(OctetString *octetstring, uint8_t *buffer, uint32_t buflen)
+int encode_octet_string(const OctetString *octetstring, uint8_t *buffer, uint32_t buflen)
 {
   if (octetstring != NULL) {
 	if ((octetstring->value != NULL) && (octetstring->length > 0)) {
@@ -71,7 +70,7 @@ int encode_octet_string(OctetString *octetstring, uint8_t *buffer, uint32_t bufl
   }
 }
 
-int decode_octet_string(OctetString *octetstring, uint16_t pdulen, uint8_t *buffer, uint32_t buflen)
+int decode_octet_string(OctetString *octetstring, uint16_t pdulen, const uint8_t *buffer, uint32_t buflen)
 {
   if (buflen < pdulen)
     return -1;
diff --git a/openair3/NAS/COMMON/UTIL/OctetString.h b/openair3/NAS/COMMON/UTIL/OctetString.h
index 2223b67ece..fcfe6d46b4 100644
--- a/openair3/NAS/COMMON/UTIL/OctetString.h
+++ b/openair3/NAS/COMMON/UTIL/OctetString.h
@@ -58,9 +58,9 @@ OctetString* dup_octet_string(OctetString*octetstring);
 
 void free_octet_string(OctetString *octetstring);
 
-int encode_octet_string(OctetString *octetstring, uint8_t *buffer, uint32_t len);
+int encode_octet_string(const OctetString *octetstring, uint8_t *buffer, uint32_t len);
 
-int decode_octet_string(OctetString *octetstring, uint16_t pdulen, uint8_t *buffer, uint32_t buflen);
+int decode_octet_string(OctetString *octetstring, uint16_t pdulen, const uint8_t *buffer, uint32_t buflen);
 
 char* dump_octet_string_xml(const OctetString * const octetstring);
 
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGCNasMessageContainer.c b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGCNasMessageContainer.c
index 9c317c59d5..d06521c88c 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGCNasMessageContainer.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGCNasMessageContainer.c
@@ -60,7 +60,7 @@ int decode_fgc_nas_message_container(FGCNasMessageContainer *nasmessagecontainer
 
   return decoded;
 }
-int encode_fgc_nas_message_container(FGCNasMessageContainer *nasmessagecontainer, uint8_t iei, uint8_t *buffer, uint32_t len)
+int encode_fgc_nas_message_container(const FGCNasMessageContainer *nasmessagecontainer, uint8_t iei, uint8_t *buffer, uint32_t len)
 {
   uint32_t encoded = 0;
   int encode_result;
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGCNasMessageContainer.h b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGCNasMessageContainer.h
index 5e9c8aac12..a81c1add67 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGCNasMessageContainer.h
+++ b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGCNasMessageContainer.h
@@ -44,7 +44,7 @@ typedef struct FGCNasMessageContainer_tag {
   OctetString nasmessagecontainercontents;
 } FGCNasMessageContainer;
 
-int encode_fgc_nas_message_container(FGCNasMessageContainer *nasmessagecontainer, uint8_t iei, uint8_t *buffer, uint32_t len);
+int encode_fgc_nas_message_container(const FGCNasMessageContainer *nasmessagecontainer, uint8_t iei, uint8_t *buffer, uint32_t len);
 
 int decode_fgc_nas_message_container(FGCNasMessageContainer *nasmessagecontainer, uint8_t iei, uint8_t *buffer, uint32_t len);
 
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGMMCapability.c b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGMMCapability.c
index 3a275ced7f..c053070518 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGMMCapability.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGMMCapability.c
@@ -35,7 +35,7 @@
 #include "TLVDecoder.h"
 #include "FGMMCapability.h"
 
-int encode_5gmm_capability(FGMMCapability *fgmmcapability, uint8_t iei, uint8_t *buffer, uint32_t len)
+int encode_5gmm_capability(const FGMMCapability *fgmmcapability, uint8_t iei, uint8_t *buffer, uint32_t len)
 {
   int encoded = 0;
   if (iei) {
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGMMCapability.h b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGMMCapability.h
index a28ba2ff3b..b125935f9d 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGMMCapability.h
+++ b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGMMCapability.h
@@ -42,6 +42,6 @@ typedef struct {
   uint8_t value;
 } FGMMCapability;
 
-int encode_5gmm_capability(FGMMCapability *fgmmcapability, uint8_t iei, uint8_t *buffer, uint32_t len);
+int encode_5gmm_capability(const FGMMCapability *fgmmcapability, uint8_t iei, uint8_t *buffer, uint32_t len);
 
 #endif /* FGMM_CAPABILITY_H_ */
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSMobileIdentity.c b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSMobileIdentity.c
index 6407448279..7e1489ac81 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSMobileIdentity.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSMobileIdentity.c
@@ -41,11 +41,11 @@
 
 static int decode_guti_5gs_mobile_identity(Guti5GSMobileIdentity_t *guti, const uint8_t *buffer);
 
-static int encode_guti_5gs_mobile_identity(Guti5GSMobileIdentity_t *guti, uint8_t *buffer);
-static int encode_suci_5gs_mobile_identity(Suci5GSMobileIdentity_t *suci, uint8_t *buffer);
-static int encode_imeisv_5gs_mobile_identity(Imeisv5GSMobileIdentity_t *imeisv, uint8_t *buffer);
+static int encode_guti_5gs_mobile_identity(const Guti5GSMobileIdentity_t *guti, uint8_t *buffer);
+static int encode_suci_5gs_mobile_identity(const Suci5GSMobileIdentity_t *suci, uint8_t *buffer);
+static int encode_imeisv_5gs_mobile_identity(const Imeisv5GSMobileIdentity_t *imeisv, uint8_t *buffer);
 
-int encode_stmsi_5gs_mobile_identity(uint8_t *buffer, Stmsi5GSMobileIdentity_t *stmsi, uint32_t len)
+int encode_stmsi_5gs_mobile_identity(uint8_t *buffer, const Stmsi5GSMobileIdentity_t *stmsi, uint32_t len)
 {
   // Return if buffer is shorter than min length
   if (len < LEN_5G_FGS_TMSI_IE)
@@ -126,7 +126,7 @@ int decode_5gs_mobile_identity(FGSMobileIdentity *fgsmobileidentity, uint8_t iei
   return (decoded + decoded_rc);
 }
 
-int encode_5gs_mobile_identity(FGSMobileIdentity *fgsmobileidentity, uint8_t iei, uint8_t *buffer, uint32_t len)
+int encode_5gs_mobile_identity(const FGSMobileIdentity *fgsmobileidentity, uint8_t iei, uint8_t *buffer, uint32_t len)
 {
   // Return if buffer is shorter than min length
   if (len < MIN_LEN_FGS_MOBILE_ID_IE)
@@ -222,7 +222,7 @@ static int decode_guti_5gs_mobile_identity(Guti5GSMobileIdentity_t *guti, const
   return decoded;
 }
 
-static int encode_guti_5gs_mobile_identity(Guti5GSMobileIdentity_t *guti, uint8_t *buffer)
+static int encode_guti_5gs_mobile_identity(const Guti5GSMobileIdentity_t *guti, uint8_t *buffer)
 {
   uint32_t encoded = 0;
   uint16_t temp;
@@ -245,7 +245,7 @@ static int encode_guti_5gs_mobile_identity(Guti5GSMobileIdentity_t *guti, uint8_
   return encoded;
 }
 
-static int encode_suci_5gs_mobile_identity(Suci5GSMobileIdentity_t *suci, uint8_t *buffer)
+static int encode_suci_5gs_mobile_identity(const Suci5GSMobileIdentity_t *suci, uint8_t *buffer)
 {
   uint32_t encoded = 0;
   *(buffer + encoded) = (suci->supiformat << 4) | (suci->typeofidentity);
@@ -269,7 +269,7 @@ static int encode_suci_5gs_mobile_identity(Suci5GSMobileIdentity_t *suci, uint8_
   *(buffer + encoded) = suci->homenetworkpki;
   encoded++;
 
-  char *ptr = suci->schemeoutput;
+  const char *ptr = suci->schemeoutput;
   while (ptr < suci->schemeoutput + strlen(suci->schemeoutput)) {
     buffer[encoded] = ((*(ptr + 1) - '0') << 4) | (*(ptr) - '0');
     encoded++;
@@ -281,7 +281,7 @@ static int encode_suci_5gs_mobile_identity(Suci5GSMobileIdentity_t *suci, uint8_
   return encoded;
 }
 
-static int encode_imeisv_5gs_mobile_identity(Imeisv5GSMobileIdentity_t *imeisv, uint8_t *buffer)
+static int encode_imeisv_5gs_mobile_identity(const Imeisv5GSMobileIdentity_t *imeisv, uint8_t *buffer)
 {
   uint32_t encoded = 0;
   *(buffer + encoded) = 0x00 | (imeisv->digittac01 << 4) | (imeisv->oddeven << 3) | (imeisv->typeofidentity);
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSMobileIdentity.h b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSMobileIdentity.h
index a66b74dc51..b7e66019cc 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSMobileIdentity.h
+++ b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSMobileIdentity.h
@@ -148,11 +148,11 @@ typedef union FGSMobileIdentity_tag {
 } FGSMobileIdentity;
 // clang-format on
 
-int encode_5gs_mobile_identity(FGSMobileIdentity *fgsmobileidentity, uint8_t iei, uint8_t *buffer, uint32_t len);
+int encode_5gs_mobile_identity(const FGSMobileIdentity *fgsmobileidentity, uint8_t iei, uint8_t *buffer, uint32_t len);
 
 int decode_5gs_mobile_identity(FGSMobileIdentity *fgsmobileidentity, uint8_t iei, const uint8_t *buffer, uint32_t len);
 
-int encode_stmsi_5gs_mobile_identity(uint8_t *buffer, Stmsi5GSMobileIdentity_t *stmsi, uint32_t len);
+int encode_stmsi_5gs_mobile_identity(uint8_t *buffer, const Stmsi5GSMobileIdentity_t *stmsi, uint32_t len);
 int decode_stmsi_5gs_mobile_identity(Stmsi5GSMobileIdentity_t *stmsi, const uint8_t *buffer, uint32_t len);
 
 #endif /* FGS MOBILE IDENTITY_H_ */
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationResult.c b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationResult.c
index 88eb1b810b..739cee7973 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationResult.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationResult.c
@@ -46,7 +46,7 @@ int decode_fgs_registration_result(FGSRegistrationResult *fgsregistrationresult,
   return decoded;
 }
 
-uint16_t encode_fgs_registration_result(FGSRegistrationResult *fgsregistrationresult)
+uint16_t encode_fgs_registration_result(const FGSRegistrationResult *fgsregistrationresult)
 {
   uint16_t bufferReturn;
   uint16_t *buffer = &bufferReturn;
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationResult.h b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationResult.h
index b792dad13c..04f45417b8 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationResult.h
+++ b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationResult.h
@@ -48,7 +48,7 @@ typedef struct {
   uint8_t registrationresult: 3;
 } FGSRegistrationResult;
 
-uint16_t encode_fgs_registration_result(FGSRegistrationResult *fgsregistrationresult);
+uint16_t encode_fgs_registration_result(const FGSRegistrationResult *fgsregistrationresult);
 
 int decode_fgs_registration_result(FGSRegistrationResult *fgsregistrationresult, uint8_t iei, uint16_t value, uint32_t len);
 
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationType.c b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationType.c
index d50d7bc852..81825f585a 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationType.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationType.c
@@ -49,7 +49,7 @@ int decode_5gs_registration_type(FGSRegistrationType *fgsregistrationtype, uint8
   return decoded;
 }
 
-int encode_5gs_registration_type(FGSRegistrationType *fgsregistrationtype)
+int encode_5gs_registration_type(const FGSRegistrationType *fgsregistrationtype)
 {
   uint8_t bufferReturn;
   uint8_t *buffer = &bufferReturn;
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationType.h b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationType.h
index 4298a33504..ea42ac160e 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationType.h
+++ b/openair3/NAS/NR_UE/5GS/5GMM/IES/FGSRegistrationType.h
@@ -47,7 +47,7 @@ typedef uint8_t FGSRegistrationType;
 #define EMERGENCY_REGISTRATION             0b100
 // clang-format on
 
-int encode_5gs_registration_type(FGSRegistrationType *fgsregistrationtype);
+int encode_5gs_registration_type(const FGSRegistrationType *fgsregistrationtype);
 
 int decode_5gs_registration_type(FGSRegistrationType *fgsregistrationtype, uint8_t iei, uint8_t value, uint32_t len);
 
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/IES/NrUESecurityCapability.c b/openair3/NAS/NR_UE/5GS/5GMM/IES/NrUESecurityCapability.c
index d069b50a39..5d2d7cc040 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/IES/NrUESecurityCapability.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/IES/NrUESecurityCapability.c
@@ -35,7 +35,10 @@
 #include "TLVDecoder.h"
 #include "NrUESecurityCapability.h"
 
-int encode_nrue_security_capability(NrUESecurityCapability *nruesecuritycapability, uint8_t iei, uint8_t *buffer, uint32_t len)
+int encode_nrue_security_capability(const NrUESecurityCapability *nruesecuritycapability,
+                                    uint8_t iei,
+                                    uint8_t *buffer,
+                                    uint32_t len)
 {
   int encoded = 0;
   if (iei) {
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/IES/NrUESecurityCapability.h b/openair3/NAS/NR_UE/5GS/5GMM/IES/NrUESecurityCapability.h
index b772feeba7..a8ee4391b3 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/IES/NrUESecurityCapability.h
+++ b/openair3/NAS/NR_UE/5GS/5GMM/IES/NrUESecurityCapability.h
@@ -45,6 +45,9 @@ typedef struct {
   uint8_t EIA;
 } NrUESecurityCapability;
 
-int encode_nrue_security_capability(NrUESecurityCapability *nruesecuritycapability, uint8_t iei, uint8_t *buffer, uint32_t len);
+int encode_nrue_security_capability(const NrUESecurityCapability *nruesecuritycapability,
+                                    uint8_t iei,
+                                    uint8_t *buffer,
+                                    uint32_t len);
 
 #endif /* NRUE_SECURITY_CAPABILITY_H_ */
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/IES/SORTransparentContainer.c b/openair3/NAS/NR_UE/5GS/5GMM/IES/SORTransparentContainer.c
index 3bbcb89f92..9a6af8517c 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/IES/SORTransparentContainer.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/IES/SORTransparentContainer.c
@@ -30,7 +30,10 @@
 
 //#define NAS_DEBUG 1
 
-int decode_sor_transparent_container(SORTransparentContainer *sortransparentcontainer, uint8_t iei, uint8_t *buffer, uint32_t len)
+int decode_sor_transparent_container(SORTransparentContainer *sortransparentcontainer,
+                                     uint8_t iei,
+                                     const uint8_t *buffer,
+                                     uint32_t len)
 {
   int decoded = 0;
   int decode_result;
@@ -61,7 +64,10 @@ int decode_sor_transparent_container(SORTransparentContainer *sortransparentcont
   LOG_FUNC_RETURN(decoded);
 }
 
-int encode_sor_transparent_container(SORTransparentContainer *sortransparentcontainer, uint8_t iei, uint8_t *buffer, uint32_t len)
+int encode_sor_transparent_container(const SORTransparentContainer *sortransparentcontainer,
+                                     uint8_t iei,
+                                     uint8_t *buffer,
+                                     uint32_t len)
 {
   uint8_t *lenPtr;
   uint32_t encoded = 0;
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/IES/SORTransparentContainer.h b/openair3/NAS/NR_UE/5GS/5GMM/IES/SORTransparentContainer.h
index 652710c0b3..7ed4e039ef 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/IES/SORTransparentContainer.h
+++ b/openair3/NAS/NR_UE/5GS/5GMM/IES/SORTransparentContainer.h
@@ -35,9 +35,15 @@ typedef struct SORTransparentContainer_tag {
   OctetString sortransparentcontainercontents;
 } SORTransparentContainer;
 
-int encode_sor_transparent_container(SORTransparentContainer *sortransparentcontainer, uint8_t iei, uint8_t *buffer, uint32_t len);
+int encode_sor_transparent_container(const SORTransparentContainer *sortransparentcontainer,
+                                     uint8_t iei,
+                                     uint8_t *buffer,
+                                     uint32_t len);
 
-int decode_sor_transparent_container(SORTransparentContainer *sortransparentcontainer, uint8_t iei, uint8_t *buffer, uint32_t len);
+int decode_sor_transparent_container(SORTransparentContainer *sortransparentcontainer,
+                                     uint8_t iei,
+                                     const uint8_t *buffer,
+                                     uint32_t len);
 
 void dump_sor_transparent_container_xml(SORTransparentContainer *sortransparentcontainer, uint8_t iei);
 
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSAuthenticationResponse.c b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSAuthenticationResponse.c
index d93f03aed5..319026f9ef 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSAuthenticationResponse.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSAuthenticationResponse.c
@@ -37,7 +37,9 @@
 
 #include "FGSAuthenticationResponse.h"
 
-int encode_fgs_authentication_response(fgs_authentication_response_msg *authentication_response, uint8_t *buffer, uint32_t len)
+int encode_fgs_authentication_response(const fgs_authentication_response_msg *authentication_response,
+                                       uint8_t *buffer,
+                                       uint32_t len)
 {
   int encoded = 0;
   int encode_result = 0;
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSAuthenticationResponse.h b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSAuthenticationResponse.h
index d67e43bb7b..6f5427531b 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSAuthenticationResponse.h
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSAuthenticationResponse.h
@@ -57,6 +57,8 @@ typedef struct fgs_authentication_response_msg_tag {
   AuthenticationResponseParameter authenticationresponseparameter;
 } fgs_authentication_response_msg;
 
-int encode_fgs_authentication_response(fgs_authentication_response_msg *authentication_response, uint8_t *buffer, uint32_t len);
+int encode_fgs_authentication_response(const fgs_authentication_response_msg *authentication_response,
+                                       uint8_t *buffer,
+                                       uint32_t len);
 
 #endif /* ! defined(FGS_AUTHENTICATION_RESPONSE_H_) */
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSDeregistrationRequestUEOriginating.c b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSDeregistrationRequestUEOriginating.c
index 6e1c0f102e..dbe1a548fb 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSDeregistrationRequestUEOriginating.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSDeregistrationRequestUEOriginating.c
@@ -32,12 +32,12 @@
 
 #define IEI_NULL 0x00
 
-int encode_fgs_deregistration_request_ue_originating(fgs_deregistration_request_ue_originating_msg *drr,
+int encode_fgs_deregistration_request_ue_originating(const fgs_deregistration_request_ue_originating_msg *drr,
                                                      uint8_t *buffer,
                                                      uint32_t len)
 {
   int encoded = 0;
-  FGSDeregistrationType *dt = &drr->deregistrationtype;
+  const FGSDeregistrationType *dt = &drr->deregistrationtype;
   *(buffer + encoded) = ((dt->switchoff & 0x1) << 7) | ((dt->reregistration_required & 0x1) << 6) | ((dt->access_type & 0x3) << 4);
 
   int encode_result;
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSDeregistrationRequestUEOriginating.h b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSDeregistrationRequestUEOriginating.h
index 566c00c11c..3c3bf3114f 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSDeregistrationRequestUEOriginating.h
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSDeregistrationRequestUEOriginating.h
@@ -47,7 +47,7 @@ typedef struct fgs_deregistration_request_ue_originating_msg_tag {
   FGSMobileIdentity fgsmobileidentity;
 } fgs_deregistration_request_ue_originating_msg;
 
-int encode_fgs_deregistration_request_ue_originating(fgs_deregistration_request_ue_originating_msg *registrationrequest,
+int encode_fgs_deregistration_request_ue_originating(const fgs_deregistration_request_ue_originating_msg *registrationrequest,
                                                      uint8_t *buffer,
                                                      uint32_t len);
 
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSNASSecurityModeComplete.c b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSNASSecurityModeComplete.c
index 369f3a3e2d..f24dc50749 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSNASSecurityModeComplete.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSNASSecurityModeComplete.c
@@ -33,7 +33,7 @@
 #include "FGCNasMessageContainer.h"
 #include "FGSMobileIdentity.h"
 
-int encode_fgs_security_mode_complete(fgs_security_mode_complete_msg *fgs_security_mode_comp, uint8_t *buffer, uint32_t len)
+int encode_fgs_security_mode_complete(const fgs_security_mode_complete_msg *fgs_security_mode_comp, uint8_t *buffer, uint32_t len)
 {
   int encoded = 0;
   int encode_result = 0;
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSNASSecurityModeComplete.h b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSNASSecurityModeComplete.h
index 36ec4ed2b2..01f6cc15d4 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSNASSecurityModeComplete.h
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSNASSecurityModeComplete.h
@@ -54,6 +54,6 @@ typedef struct fgs_security_mode_complete_msg_tag {
   FGCNasMessageContainer fgsnasmessagecontainer;
 } fgs_security_mode_complete_msg;
 
-int encode_fgs_security_mode_complete(fgs_security_mode_complete_msg *fgs_security_mode_comp, uint8_t *buffer, uint32_t len);
+int encode_fgs_security_mode_complete(const fgs_security_mode_complete_msg *fgs_security_mode_comp, uint8_t *buffer, uint32_t len);
 
 #endif /* ! defined(FGS_NAS_SECURITY_MODE_COMPLETE_H_) */
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSUplinkNasTransport.c b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSUplinkNasTransport.c
index 26d2e9ad61..6b1b748146 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSUplinkNasTransport.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSUplinkNasTransport.c
@@ -34,7 +34,7 @@
 #include <string.h>
 #include "TLVEncoder.h"
 
-int encode_fgs_payload_container(FGSPayloadContainer *paycontainer, uint8_t iei, uint8_t *buffer, uint32_t len)
+static int encode_fgs_payload_container(const FGSPayloadContainer *paycontainer, uint8_t iei, uint8_t *buffer, uint32_t len)
 {
   uint32_t encoded = 0;
   int encode_result;
@@ -62,7 +62,7 @@ int encode_fgs_payload_container(FGSPayloadContainer *paycontainer, uint8_t iei,
   return encoded;
 }
 
-int encode_nssai(OctetString *nssai, uint8_t iei, uint8_t *buffer)
+static int encode_nssai(const OctetString *nssai, uint8_t iei, uint8_t *buffer)
 {
   uint32_t encoded = 0;
   int encode_result;
@@ -84,7 +84,7 @@ int encode_nssai(OctetString *nssai, uint8_t iei, uint8_t *buffer)
   return encoded;
 }
 
-int encode_dnn(OctetString *dnn, uint8_t iei, uint8_t *buffer)
+static int encode_dnn(const OctetString *dnn, uint8_t iei, uint8_t *buffer)
 {
   uint32_t encoded = 0;
   int encode_result;
@@ -106,7 +106,7 @@ int encode_dnn(OctetString *dnn, uint8_t iei, uint8_t *buffer)
   return encoded;
 }
 
-int encode_fgs_uplink_nas_transport(fgs_uplink_nas_transport_msg *fgs_up_nas_transport, uint8_t *buffer, uint32_t len)
+int encode_fgs_uplink_nas_transport(const fgs_uplink_nas_transport_msg *fgs_up_nas_transport, uint8_t *buffer, uint32_t len)
 {
   int encoded = 0;
   int encode_result = 0;
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSUplinkNasTransport.h b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSUplinkNasTransport.h
index 6c045d7d48..06ade93896 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSUplinkNasTransport.h
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSUplinkNasTransport.h
@@ -66,6 +66,6 @@ typedef struct fgs_uplink_nas_transport_msg_tag {
   OctetString dnn;
 } fgs_uplink_nas_transport_msg;
 
-int encode_fgs_uplink_nas_transport(fgs_uplink_nas_transport_msg *fgs_security_mode_comp, uint8_t *buffer, uint32_t len);
+int encode_fgs_uplink_nas_transport(const fgs_uplink_nas_transport_msg *fgs_security_mode_comp, uint8_t *buffer, uint32_t len);
 
 #endif /* ! defined(FGS_UPLINK_NAS_TRANSPORT_H_) */
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationAccept.c b/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationAccept.c
index b110ca75a3..bca9dff06a 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationAccept.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationAccept.c
@@ -65,7 +65,7 @@ int decode_registration_accept(registration_accept_msg *registration_accept, con
   return decoded;
 }
 
-int encode_registration_accept(registration_accept_msg *registration_accept, uint8_t *buffer, uint32_t len)
+int encode_registration_accept(const registration_accept_msg *registration_accept, uint8_t *buffer, uint32_t len)
 {
   int encoded = 0;
 
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationAccept.h b/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationAccept.h
index 61c987db4b..d48a8f21d4 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationAccept.h
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationAccept.h
@@ -61,6 +61,6 @@ typedef struct registration_accept_msg_tag {
 
 int decode_registration_accept(registration_accept_msg *registrationaccept, const uint8_t *buffer, uint32_t len);
 
-int encode_registration_accept(registration_accept_msg *registrationaccept, uint8_t *buffer, uint32_t len);
+int encode_registration_accept(const registration_accept_msg *registrationaccept, uint8_t *buffer, uint32_t len);
 
 #endif /* ! defined(REGISTRATION_ACCEPT_H_) */
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationComplete.c b/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationComplete.c
index 702b3ab600..0ce14cdcd8 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationComplete.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationComplete.c
@@ -23,14 +23,14 @@
 #include <stdint.h>
 #include "SORTransparentContainer.h"
 
-int decode_registration_complete(registration_complete_msg *registration_complete, uint8_t *buffer, uint32_t len)
+int decode_registration_complete(registration_complete_msg *registration_complete, const uint8_t *buffer, uint32_t len)
 {
   uint32_t decoded = 0;
   int decoded_result = 0;
 
   /* Decoding mandatory fields */
   if ((decoded_result =
-           decode_sor_transparent_container(&registration_complete->sortransparentcontainer, 0, buffer + decoded, len - decoded))
+           decode_sor_transparent_container(registration_complete->sortransparentcontainer, 0, buffer + decoded, len - decoded))
       < 0)
     return decoded_result;
   else
@@ -39,7 +39,7 @@ int decode_registration_complete(registration_complete_msg *registration_complet
   return decoded;
 }
 
-int encode_registration_complete(registration_complete_msg *registration_complete, uint8_t *buffer, uint32_t len)
+int encode_registration_complete(const registration_complete_msg *registration_complete, uint8_t *buffer, uint32_t len)
 {
   int encoded = 0;
   int encode_result = 0;
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationComplete.h b/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationComplete.h
index e97c8d262d..1c2141243a 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationComplete.h
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationComplete.h
@@ -41,8 +41,8 @@ typedef struct registration_complete_msg_tag {
   SORTransparentContainer *sortransparentcontainer;
 } registration_complete_msg;
 
-int decode_registration_complete(registration_complete_msg *registrationcomplete, uint8_t *buffer, uint32_t len);
+int decode_registration_complete(registration_complete_msg *registrationcomplete, const uint8_t *buffer, uint32_t len);
 
-int encode_registration_complete(registration_complete_msg *registrationcomplete, uint8_t *buffer, uint32_t len);
+int encode_registration_complete(const registration_complete_msg *registrationcomplete, uint8_t *buffer, uint32_t len);
 
 #endif /* ! defined(REGISTRATION_COMPLETE_H_) */
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationRequest.c b/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationRequest.c
index dd08e61dba..8f6fea900e 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationRequest.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationRequest.c
@@ -34,7 +34,7 @@
 
 #define IEI_NULL 0x00
 
-int decode_registration_request(registration_request_msg *registration_request, uint8_t *buffer, uint32_t len)
+int decode_registration_request(registration_request_msg *registration_request, const uint8_t *buffer, uint32_t len)
 {
   uint32_t decoded = 0;
   int decoded_result = 0;
@@ -68,7 +68,7 @@ int decode_registration_request(registration_request_msg *registration_request,
   return decoded;
 }
 
-int encode_registration_request(registration_request_msg *registration_request, uint8_t *buffer, uint32_t len)
+int encode_registration_request(const registration_request_msg *registration_request, uint8_t *buffer, uint32_t len)
 {
   int encoded = 0;
   int encode_result = 0;
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationRequest.h b/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationRequest.h
index 3ae943a5f1..9112fa6795 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationRequest.h
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationRequest.h
@@ -112,8 +112,8 @@ typedef struct registration_request_msg_tag {
   NrUESecurityCapability nruesecuritycapability;
 } registration_request_msg;
 
-int decode_registration_request(registration_request_msg *registrationrequest, uint8_t *buffer, uint32_t len);
+int decode_registration_request(registration_request_msg *registrationrequest, const uint8_t *buffer, uint32_t len);
 
-int encode_registration_request(registration_request_msg *registrationrequest, uint8_t *buffer, uint32_t len);
+int encode_registration_request(const registration_request_msg *registrationrequest, uint8_t *buffer, uint32_t len);
 
 #endif /* ! defined(REGISTRATION_REQUEST_H_) */
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/fgs_service_request.c b/openair3/NAS/NR_UE/5GS/5GMM/MSG/fgs_service_request.c
index fa31e1e297..4603db55c5 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/fgs_service_request.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/fgs_service_request.c
@@ -38,7 +38,7 @@
 /**
  * @brief Encode 5GMM NAS Service Request message (8.2.16 of 3GPP TS 24.501)
  */
-int encode_fgs_service_request(uint8_t *buffer, fgs_service_request_msg_t *service_request, uint32_t len)
+int encode_fgs_service_request(uint8_t *buffer, const fgs_service_request_msg_t *service_request, uint32_t len)
 {
   // Return if buffer is shorter than min length
   if (len < MIN_LEN_FGS_SERVICE_REQUEST)
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/fgs_service_request.h b/openair3/NAS/NR_UE/5GS/5GMM/MSG/fgs_service_request.h
index 79c7c00c62..82a721d52a 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/fgs_service_request.h
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/fgs_service_request.h
@@ -53,7 +53,7 @@ typedef struct {
   FGCNasMessageContainer *fgsnasmessagecontainer;
 } fgs_service_request_msg_t;
 
-int encode_fgs_service_request(uint8_t *buffer, fgs_service_request_msg_t *servicerequest, uint32_t len);
+int encode_fgs_service_request(uint8_t *buffer, const fgs_service_request_msg_t *servicerequest, uint32_t len);
 int decode_fgs_service_request(fgs_service_request_msg_t *sr, const uint8_t *buffer, uint32_t len);
 
 #endif /* ! defined(FGS_SERVICE_REQUEST_H_) */