diff --git a/trial3/layer1.c b/trial3/layer1.c
index b0e4b7c..9cac60b 100644
--- a/trial3/layer1.c
+++ b/trial3/layer1.c
@@ -100,33 +100,33 @@ int _calcCDID(uint8_t * CDID)
   uint8_t* FW_ID = calloc(1,sizeof(uint8_t)*FW_DGST_SIZE);
   readFWID(FW_ID);
 
-  mbedtls_sha256_context * sha_ctx;
-  mbedtls_sha256_init(sha_ctx);
-  if(mbedtls_sha256_starts_ret(sha_ctx,0) < 0 )
+  mbedtls_sha256_context sha_ctx;
+  mbedtls_sha256_init(&sha_ctx);
+  if(mbedtls_sha256_starts_ret(&sha_ctx,0) < 0 )
   {
     perror("SHA session failed to start\n");
-    mbedtls_sha256_free(sha_ctx);
+    mbedtls_sha256_free(&sha_ctx);
     return -1;
   }
 
-  if(mbedtls_sha256_update_ret(sha_ctx, UDS_ID, UDS_DGST_SIZE) < 0)
+  if(mbedtls_sha256_update_ret(&sha_ctx, UDS_ID, UDS_DGST_SIZE) < 0)
   {
     perror("SHA session update failed\n");
-    mbedtls_sha256_free(sha_ctx);
+    mbedtls_sha256_free(&sha_ctx);
     return -1;  
   }
 
-  if(mbedtls_sha256_update_ret(sha_ctx, FW_ID, FW_DGST_SIZE) < 0)
+  if(mbedtls_sha256_update_ret(&sha_ctx, FW_ID, FW_DGST_SIZE) < 0)
   {
     perror("SHA session update failed\n");
-    mbedtls_sha256_free(sha_ctx);
+    mbedtls_sha256_free(&sha_ctx);
     return -1;  
   }  
 
-  if(mbedtls_sha256_finish_ret(sha_ctx,CDID) < 0)
+  if(mbedtls_sha256_finish_ret(&sha_ctx,CDID) < 0)
   {
     perror("SHA session update failed\n");
-    mbedtls_sha256_free(sha_ctx);
+    mbedtls_sha256_free(&sha_ctx);
     return -1;  
   }
 
@@ -136,7 +136,7 @@ int _calcCDID(uint8_t * CDID)
   
   free(UDS_ID);
   free(FW_ID);
-  mbedtls_sha256_free(sha_ctx);
+  mbedtls_sha256_free(&sha_ctx);
   return RIOTSUCCESS;
 
 }