tutorial: root_of_trust: add starter code for encryption service

Author: pqcfox

examples/tutorials/root_of_trust/encryption_service_starter/Makefile

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+# Makefile for user application
+
+# Specify this directory relative to the current application.
+TOCK_USERLAND_BASE_DIR = ../../../../
+
+PACKAGE_NAME = org.tockos.tutorials.attestation.encryption
+
+# Which files to compile.
+C_SRCS := $(wildcard *.c)
+
+# Include userland master makefile. Contains rules and flags for actually
+# building the application.
+include $(TOCK_USERLAND_BASE_DIR)/AppMakefile.mk

examples/tutorials/root_of_trust/encryption_service_starter/README.md

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+Hardware Root of Trust (HWRoT) Demo Encryption Service Application
+------------------------------------------------------------------
+
+This application implements a basic UART encryption service for a mock hardware
+root of trust (HWRoT) which inputs user-provided 
+
+This is part of a tutorial which improves the application in multiple steps. A
+writeup for the tutorial is available at https://book.tockos.org/.
+
+Specific abilities of this version:
+
+* Does NOT allow logging to screen over IPC
+* Does NOT allow for plaintext over returning results in hex over UART
+* Does NOT allow for encryping user-provided plaintext using an encryption oracle driver
+
+This application is essentially just a scaffold to build from while following the tutorial.

examples/tutorials/root_of_trust/encryption_service_starter/main.c

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+// Hardware Root of Trust (HWRoT) Demo Encryption Service Application
+//
+// When selected by the main screen HWRoT Demo application, listens for user-provided
+// plaintexts over UART and encrypts them, logging status over IPC back to the screen
+// application.
+
+#include <stdio.h>
+
+int main(void) {
+  // Your code here...
+  printf("Encryption service app started!");
+}