From 50381c06244e944390de382f6bdd85cc8b9a3332 Mon Sep 17 00:00:00 2001
From: Sadeep Madurange <sadeep@asciimx.com>
Date: Wed, 6 Nov 2024 11:51:41 +0800
Subject: XOR cypher.

---
 door_lock/Makefile |  2 +-
 door_lock/main.c   | 57 ------------------------------------
 door_lock/servo.c  | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 87 insertions(+), 58 deletions(-)
 delete mode 100644 door_lock/main.c
 create mode 100644 door_lock/servo.c

diff --git a/door_lock/Makefile b/door_lock/Makefile
index c188507..92b9945 100644
--- a/door_lock/Makefile
+++ b/door_lock/Makefile
@@ -2,7 +2,7 @@ CC = avr-gcc
 MCU = atmega328p
 TARGET = app
 
-SRC = main.c serial.c
+SRC = servo.c serial.c
 OBJ = $(SRC:.c=.o)
 
 CFLAGS = -std=gnu99
diff --git a/door_lock/main.c b/door_lock/main.c
deleted file mode 100644
index d272a7f..0000000
--- a/door_lock/main.c
+++ /dev/null
@@ -1,57 +0,0 @@
-#include <stddef.h>
-
-#include <avr/io.h>
-#include <avr/interrupt.h>
-
-#define PWM_MIN 1200
-#define PWM_MID 3000
-#define PWM_MAX 5000
-
-#define SERVO_PIN  PB1
-#define LOCK_BTN   PD6
-#define UNLOCK_BTN PD7
-
-static inline void servo_init(void)
-{
-	DDRB |= 1 << SERVO_PIN;
-	TCCR1A |= (1 << WGM11) | (1 << COM1A1);
-	TCCR1B |= (1 << WGM12) | (1 << WGM13) | (1 << CS11);
-
-	ICR1 = 40000;
-
-	DDRD &= ~((1 << LOCK_BTN) | (1 << UNLOCK_BTN));
-	PORTD |= (1 << LOCK_BTN) | (1 << UNLOCK_BTN);
-}
-
-static inline void pcint2_init(void)
-{
-	PCICR |= (1 << PCIE2);
-	PCMSK2 |= ((1 << PCINT22) | (1 << PCINT23));
-}
-
-static inline uint8_t is_btn_pressed(uint8_t btn)
-{
-    return !((PIND >> btn) & 0x01);
-}
-
-int main(void) 
-{
-	servo_init();
-	pcint2_init();
-
-	sei();
-
-	for(;;)
-		;
-
-	return 0;
-}
-
-ISR(PCINT2_vect)
-{
-	if (is_btn_pressed(LOCK_BTN))
-		OCR1A = PWM_MID;
-
-	if (is_btn_pressed(UNLOCK_BTN))
-		OCR1A = PWM_MIN;
-}
diff --git a/door_lock/servo.c b/door_lock/servo.c
new file mode 100644
index 0000000..45640df
--- /dev/null
+++ b/door_lock/servo.c
@@ -0,0 +1,86 @@
+#include <stdint.h>
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <util/delay.h>
+
+#include "serial.h"
+
+#define PWM_MIN 1200
+#define PWM_MID 3000
+#define PWM_MAX 5000
+
+#define SERVO_PIN  PB1
+#define LOCK_BTN   PD6
+#define ULOCK_BTN  PD7
+
+#define XORLEN     32
+#define KEY        "dM>}jdb,6gsnC$J^K 8(I5vyPemPs%;K"
+#define ULOCK_FLAG "43iqr5$NB8SpN?Z/52{iVl>o|i!.'dsT"
+
+static inline void servo_init(void)
+{
+	DDRB |= 1 << SERVO_PIN;
+	TCCR1A |= (1 << WGM11) | (1 << COM1A1);
+	TCCR1B |= (1 << WGM12) | (1 << WGM13) | (1 << CS11);
+
+	ICR1 = 40000;
+
+	DDRD &= ~((1 << LOCK_BTN) | (1 << ULOCK_BTN));
+	PORTD |= (1 << LOCK_BTN) | (1 << ULOCK_BTN);
+}
+
+static inline void pcint2_init(void)
+{
+	PCICR |= (1 << PCIE2);
+	PCMSK2 |= ((1 << PCINT22) | (1 << PCINT23));
+}
+
+static inline uint8_t is_btn_pressed(uint8_t btn)
+{
+    return !((PIND >> btn) & 0x01);
+}
+
+static inline void xor(const char *s, char *d, uint8_t n)
+{
+	int i;
+
+	for (i = 0; i < n && s[i]; i++)
+		d[i] = s[i] ^ KEY[i];
+}
+
+int main(void) 
+{
+	char s1[XORLEN];
+	char s2[XORLEN + 1]; 
+
+	servo_init();
+	pcint2_init();
+
+	serial_init();
+
+	sei();
+
+	for(;;) {
+		// encrypt
+		xor(ULOCK_FLAG, s1, XORLEN);
+
+		// decrypt
+		xor(s1, s2, XORLEN);
+		s2[XORLEN] = 0;
+		serial_write_line(s2);
+
+		_delay_ms(1000);
+	}
+
+	return 0;
+}
+
+ISR(PCINT2_vect)
+{
+	if (is_btn_pressed(LOCK_BTN))
+		OCR1A = PWM_MID;
+
+	if (is_btn_pressed(ULOCK_BTN))
+		OCR1A = PWM_MIN;
+}
-- 
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