Implement MISRA compliant Vernam cipher/One Time Pad algorithm

- Vernam cipher/One Time Pad algorithm - MISRA compliant
IMProject · Jun 9, 2024 · 395590f · 395590f
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diff --git a/Inc/crypto/vernam_cipher.h b/Inc/crypto/vernam_cipher.h
@@ -0,0 +1,62 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2024 IMProject Development Team. All rights reserved.
+ *   Authors: Juraj Ciberlin <[email protected]>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name IMProject nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#ifndef VERNAM_CIPHER_H_
+#define VERNAM_CIPHER_H_
+
+#include "typedefs.h"
+
+/**
+ * @brief Encryption using Vernam cipher/One Time Pad algorithm.
+ *
+ * @param[in/out] *msg Pointer to message that will be encrypted.
+ * @param[in] *key Pointer to key string.
+ * @param[in] key_length Key length.
+ *
+ * @return Status of encryption function. True if message size is higher than or equal to key length, otherwise false.
+ */
+bool VernamCipher_encrypt(char* msg, const char* key, int32_t key_length);
+
+/**
+ * @brief Decryption using Vernam cipher/One Time Pad algorithm.
+ *
+ * @param[in/out] *msg Pointer to message that will be decrypted.
+ * @param[in] *key Pointer to key string.
+ * @param[in] key_length Key length.
+ *
+ * @return Status of decryption function. True if message size is higher than or equal to key length, otherwise false.
+ */
+bool VernamCipher_decrypt(char* msg, const char* key, int32_t key_length);
+
+#endif /* VERNAM_CIPHER_H_ */
diff --git a/Makefile b/Makefile
@@ -107,6 +107,7 @@ IMUTILITY_FILES=\
   Src/crc/crc32_variants/crc32_xfer.c \
   Src/crypto/caesar_cipher.c \
   Src/crypto/chacha20.c \
+  Src/crypto/vernam_cipher.c \
   Src/sort/bubble_sort.c \
   Src/sort/heap_sort.c \
   Src/sort/insertion_sort.c \
@@ -139,7 +140,8 @@ SRC_FILES+=$(IMUTILITY_FILES) \
   Tests/test_queue.c \
   Tests/test_scheduler.c \
   Tests/test_selection_sort.c \
-  Tests/test_utils.c
+  Tests/test_utils.c \
+  Tests/test_vernam_cipher.c
 
 INC_DIRS_CODE= \
   -IInc \

diff --git a/README.md b/README.md
@@ -123,6 +123,8 @@ Join us on the Discord channel https://discord.gg/R6nZxZqDH3
 - CaesarCipher_encrypt
 - CaesarCipher_decrypt
 - Chacha20_crypt
+- VernamCipher_encrypt
+- VernamCipher_decrypt
 
 ### JSON
 - Json_startString

diff --git a/Src/crypto/vernam_cipher.c b/Src/crypto/vernam_cipher.c
@@ -0,0 +1,105 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2024 IMProject Development Team. All rights reserved.
+ *   Authors: Juraj Ciberlin <[email protected]>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name IMProject nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#include "vernam_cipher.h"
+
+#include <string.h>
+
+#include "utils.h"
+
+#define UPPER_A_ASCII   (65)
+#define LOWER_A_ASCII   (97)
+#define NUM_OF_ALPHA    (26)
+
+bool
+VernamCipher_encrypt(char* msg, const char* key, int32_t key_length) {
+    bool status = false;
+    const size_t msg_length = strlen(msg);
+    if ((int32_t)msg_length == key_length) {
+        for (int32_t i = 0; i < key_length; ++i) {
+            if (Utils_isAlpha(msg[i])) {
+                int8_t c;
+                if (Utils_isLowerChar(key[i])) {
+                    c = LOWER_A_ASCII;
+                } else {
+                    c = UPPER_A_ASCII;
+                }
+
+                int32_t ascii_val;
+                if (Utils_isUpperChar(msg[i])) {
+                    ascii_val = UPPER_A_ASCII;
+                } else {
+                    ascii_val = LOWER_A_ASCII;
+                }
+
+                int32_t temp = (((int8_t)msg[i] - ascii_val + (int8_t)key[i] - c) % NUM_OF_ALPHA);
+                int32_t cipher = temp + ascii_val;
+                msg[i] = (char)cipher;
+            }
+        }
+        status = true;
+    }
+    return status;
+}
+
+bool
+VernamCipher_decrypt(char* msg, const char* key, int32_t key_length) {
+    bool status = false;
+    const size_t msg_length = strlen(msg);
+    if ((int32_t)msg_length == key_length) {
+        for (int32_t i = 0; i < key_length; ++i) {
+            if (Utils_isAlpha(msg[i])) {
+                int8_t c;
+                if (Utils_isLowerChar(key[i])) {
+                    c = LOWER_A_ASCII;
+                } else {
+                    c = UPPER_A_ASCII;
+                }
+
+                int32_t ascii_val;
+                if (Utils_isUpperChar(msg[i])) {
+                    ascii_val = UPPER_A_ASCII;
+                } else {
+                    ascii_val = LOWER_A_ASCII;
+                }
+
+                int32_t cipher = ((msg[i] - ascii_val) - (key[i] - c));
+                cipher = (cipher < 0) ? (cipher + NUM_OF_ALPHA + ascii_val) : (cipher + ascii_val);
+                msg[i] = (char)cipher;
+            }
+        }
+        status = true;
+    }
+    return status;
+}
diff --git a/Tests/test_main.c b/Tests/test_main.c
@@ -20,6 +20,7 @@ RunAllTests(void) {
     RUN_TEST_GROUP(Scheduler);
     RUN_TEST_GROUP(SelectionSort);
     RUN_TEST_GROUP(Utils);
+    RUN_TEST_GROUP(VernamCipher);
 }
 
 int

diff --git a/Tests/test_vernam_cipher.c b/Tests/test_vernam_cipher.c
@@ -0,0 +1,35 @@
+#include "vernam_cipher.h"
+
+#include <string.h>
+
+#include "unity.h"
+#include "unity_fixture.h"
+
+TEST_GROUP(VernamCipher);
+
+TEST_SETUP(VernamCipher) {
+}
+
+TEST_TEAR_DOWN(VernamCipher) {
+}
+
+TEST_GROUP_RUNNER(VernamCipher) {
+    RUN_TEST_CASE(VernamCipher, VernamCipher_encryptDecrypt);
+}
+
+TEST(VernamCipher, VernamCipher_encryptDecrypt) {
+    const char expected_result[] = "ReSuLt1a";
+    const char key1[] = "OSIJEK11";
+    const char key2[] = "OSijek!/";
+    char message[] = "ReSuLt1a";
+    TEST_ASSERT_TRUE(VernamCipher_encrypt(message, key1, (int32_t)strlen(key1)));
+    TEST_ASSERT_TRUE(VernamCipher_decrypt(message, key1, (int32_t)strlen(key1)));
+    TEST_ASSERT_EQUAL_STRING(expected_result, message);
+
+    TEST_ASSERT_TRUE(VernamCipher_encrypt(message, key2, (int32_t)strlen(key2)));
+    TEST_ASSERT_TRUE(VernamCipher_decrypt(message, key2, (int32_t)strlen(key2)));
+    TEST_ASSERT_EQUAL_STRING(expected_result, message);
+
+    TEST_ASSERT_FALSE(VernamCipher_encrypt(message, key1, 3));
+    TEST_ASSERT_FALSE(VernamCipher_decrypt(message, key1, 100));
+}