Vertical key derivation to use K_enb_initial instead of k_enb

srsue/hdr/upper/usim.h

@@ -126,6 +126,7 @@ private:
   uint8_t     autn[16];
   uint8_t     k_asme[32];
   uint8_t     nh[32];
+  uint8_t     k_enb_initial[32];
   uint8_t     k_enb[32];
   uint8_t     k_enb_star[32];
 

srsue/src/upper/usim.cc

@@ -243,6 +243,9 @@ void usim::generate_as_keys(uint8_t *k_asme,
 
   memcpy(this->k_asme, k_asme, 32);
 
+  // Save initial k_enb
+  memcpy(k_enb_initial, k_enb, 32);
+
   // Generate K_rrc_enc and K_rrc_int
   security_generate_k_rrc( k_enb,
                            cipher_algo,
@@ -282,7 +285,7 @@ void usim::generate_as_keys_ho(uint32_t pci,
     if (current_ncc) {
       sync = nh;
     } else {
-      sync = k_enb;
+      sync = k_enb_initial;
     }
     // Generate NH
     security_generate_nh(k_asme,