diff --git a/templates/esp32/src/main.ino b/templates/esp32/src/main.ino
index db8273f..24be19c 100644
--- a/templates/esp32/src/main.ino
+++ b/templates/esp32/src/main.ino
@@ -61,11 +61,16 @@ void setup() {
     memset(ad, 0, MAX_BYTES);
     memset(m, 0, MAX_BYTES);
     memset(c, 0, MAX_BYTES);
+    mlen = 8;
+    adlen = 0;
+    crypto_aead_encrypt(c, &clen, m, mlen, ad, adlen, nsec, npub, k);
+    crypto_aead_decrypt(m, &mlen, nsec, c, clen, ad, adlen, npub, k);
     SerialOut.print("Hello, World!");
 }
 
 void loop() {
     int res;
+    portMUX_TYPE mux = portMUX_INITIALIZER_UNLOCKED;
     uint16_t len = uartp_recv(cmdbuf, CMDBUF_LEN - 1);
     uint8_t action = cmdbuf[0];
     if (len == 0 || len > CMDBUF_LEN - 1)
@@ -82,22 +87,18 @@ void loop() {
         case 'p': my_assert(l == CRYPTO_NPUBBYTES); memcpy(npub, var, l); break;
         case 's': my_assert(l == CRYPTO_NSECBYTES); memcpy(nsec, var, l); break;
         case 'e':
-			noInterrupts();
-			asm("nop");
+            portENTER_CRITICAL(&mux);
             digitalWrite(CRYPTO_BUSY, LOW);
             res = crypto_aead_encrypt(c, &clen, m, mlen, ad, adlen, nsec, npub, k);
             digitalWrite(CRYPTO_BUSY, HIGH);
-			asm("nop");
-			interrupts();
+            portEXIT_CRITICAL(&mux);
             break;
         case 'd':
-			noInterrupts();
-			asm("nop");
+            portENTER_CRITICAL(&mux);
             digitalWrite(CRYPTO_BUSY, LOW);
             res = crypto_aead_decrypt(m, &mlen, nsec, c, clen, ad, adlen, npub, k);
             digitalWrite(CRYPTO_BUSY, HIGH);
-			asm("nop");
-			interrupts();
+            portEXIT_CRITICAL(&mux);
             break;
         case'M': var = m;    rl = mlen; break;
         case'C': var = c;    rl = clen; break;