main: need polish, almost done

.gitignore

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+build/
+massif*
+dhat*
+.vimspector.json

Makefile

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+.PHONY: all test clean build
+
+SRC 	= src/main.c
+OJB 	= $(SRC:.c=.o)
+OUT 	= build
+
+CC 		= /usr/bin/gcc
+CFLAGS 	= -ansi -Wall -std=c99 -O0
+CFDEBUG = -ansi -Wall -g -std=c99 
+RM 		= /bin/rm -fr 
+TEST 	= -D TEST_TECH
+PART 	= -D PART_
+EVE 	= -D EVE_
+
+%.o: %.c
+	 $(CC) -c $(CFLAGS)
+
+build:
+	$(CC)  $(SRC) $(PART)$(part) $(EVE)$(eve) $(CFLAGS) -o $(OUT)/main.o
+
+build_test:
+	$(CC) $(SRC) $(CFLAGS) $(TEST) -o $(OUT)/main.o
+
+debug:
+	$(CC) $(SRC) $(PART)$(part) $(CFDEBUG) -o $(OUT)/main.o
+
+clean:
+	$(RM) $(OBJ) $(OUT)/main.o
+
+run:
+	$(MAKE) build  && ./build/main.o
+
+test: 
+	 $(MAKE) build_test && ./build/main.o

src/main.c

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+/*
+ * ----------------------------------------------------------------------------
+ * "THE BEER-WARE LICENSE" (Revision 42):
+ * <paum1202@usherbrooke.ca> wrote this file.  As long as you retain this notice you
+ * can do whatever you want with this stuff. If we meet some day, and you think
+ * this stuff is worth it, you can buy me a beer in return. -violette paulin 
+ * ----------------------------------------------------------------------------
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+/* get bits after n from k */
+#define LAST_BITS(k,n) ((k) & ((1 << (n)) - 1))
+/* get bits of k between m and n */
+#define MID_BITS(k,m,n) LAST_BITS((k) >> (m), ((n) - (m)))
+
+#define SIZE_ALPH 26
+#define SIZE_MSG 32
+#define SIZE_OTP 64
+
+struct eve {
+	uint32_t msg;
+	uint32_t tag;
+};
+
+static uint32_t			mac(uint32_t, uint32_t);
+static char			 	verif(uint32_t, uint32_t, uint32_t);
+static inline uint32_t	gen();
+static uint32_t			char_arr_to_uint32(char *);
+static struct eve		eve_shenanigans(struct eve);
+static char *			uint32_to_char_arr(uint32_t n);
+
+static void				print_hex(char *);
+
+int
+main(int argc, char *argv[])
+{
+	srand(time(0)); /* init rand */
+
+	uint32_t key = gen();
+	uint32_t msg = 0;
+
+#ifdef TEST_TECH
+	char *test = "yay";
+	printf("Testing char_arr_to_uint32 and uint32_to_char_arr: \n");
+	printf("%s\n", uint32_to_char_arr(char_arr_to_uint32(test)));
+#endif
+
+	printf("\n--- MSG ---\nas 0x: ");
+#ifdef PART_ZERO
+	msg = 0;
+	printf("0x00000000\n");
+#endif
+
+#ifdef PART_MAX
+	msg = UINT32_MAX;
+	printf("0xffffffff\n");
+#endif
+
+#ifdef PART_MID
+	printf("0x0000ffff\n");
+	/* is UINT16_MAX, but keeping this way for corrector convenience */
+	msg = UINT32_MAX & UINT16_MAX;
+#endif
+
+#ifdef PART_NAME
+	msg = *(uint32_t *)"bob";
+	printf("%u\n", msg);
+#endif
+
+	printf("as char *: %s\nas uint32: %u\n",
+			uint32_to_char_arr(msg), msg);
+
+	uint32_t tag = mac(msg, key);
+	printf("--- TAG ---\n%d \n", tag);
+
+	printf("--- VERIF ---\n%d\n", 
+			verif(key, msg, tag));
+
+	printf("\n--- ALICE ---\n");
+	printf("sends msg: %u\nsends tag: %u\n", msg, tag);
+	printf("knows key: %u\n", key);
+
+	printf("\n--- EVE ---\n");
+	printf("recieves msg: %u\nrecieves tag: %u\n", msg, tag);
+	struct eve tmp = { msg, tag };
+	tmp = eve_shenanigans(tmp);
+	msg = tmp.msg, tag = tmp.tag;
+	printf("sends msg: %u\nsends tag: %u\n", msg, tag);
+
+	printf("\n--- BOB ---\n");
+	printf("recieves msg: %u\nrecieves tag: %u\n", msg, tag);
+	printf("knows key: %u\n", key);
+	char res = verif(msg, tag, key);
+	printf("verifies: %s\n", res ? "TRUE" : "FALSE");
+	if (res)
+		printf("msg as char *: %s\n", uint32_to_char_arr(msg));
+
+	return 0;
+}
+
+static uint32_t
+gen()
+{
+	/* rand is between 0 and UINT32_MAX - 1 / 2 (because sign) */
+	return rand() + rand() + (rand() % 1);
+}
+
+static struct eve
+eve_shenanigans(struct eve str)
+{
+#ifdef EVE_NAME
+	str.msg = *(uint32_t *)"eve";
+	str.tag = str.tag ^ (*(uint32_t *)"bob") ^ str.msg;
+#endif
+
+#ifdef EVE_ZERO
+	str.msg = UINT32_MAX;
+	str.tag = str.tag ^ 0 ^ str.msg;
+#endif
+
+	return str;
+}
+
+static char
+verif(uint32_t key, uint32_t msg, uint32_t tag)
+{
+	return (key ^ msg) == tag;
+}
+
+static uint32_t
+mac(uint32_t key, uint32_t msg)
+{
+	return msg ^ key;
+}
+
+static uint32_t
+char_arr_to_uint32(char *arr)
+{
+	return *(uint32_t *)arr;
+}
+
+static char *
+uint32_to_char_arr(uint32_t n)
+{
+	char *res = calloc(4, 1);
+	res[0] = MID_BITS(n, 0, 8);
+	res[1] = MID_BITS(n, 8, 16);
+	res[2] = MID_BITS(n, 16, 24);
+	res[3] = MID_BITS(n, 24, 32);
+
+	return res;
+}
+
+static void
+print_hex(char *str)
+{
+	short k = 0;
+	while (str[k] != '\0') {
+		printf("%02X ", str[k] & 0xff);
+		++k;
+	}
+	printf("\n");
+}