104 lines
2.4 KiB
C
104 lines
2.4 KiB
C
#include "../include/decrypter.h"
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include "../include/flags.h"
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char*
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decryptText(char *text, char *key)
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{
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//CHECK FOR INVALID key
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if (strlen(key) != KEY_LENGTH)
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{
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fprintf(stderr, "Key must be 50 characters long!\n");
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exit(INVALID_KEY);
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}
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//VARIABLES
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char *returningText;
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int numberBuffer;
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char *textBuffer;
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numberBuffer = 1;
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//GET LENGTH OF returningText AND textKeyChain
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for (int i = 0; i < strlen(text); i++)
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{
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if (text[i] == ENCRYPTION_SEPARATOR) numberBuffer++;
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}
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//SET LENGTH
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returningText = malloc(numberBuffer);
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int textKeyChain[numberBuffer];
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int encryptedTextKeyChain[numberBuffer];
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//LOAD textKeyChain
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for (int i = 0; i < (sizeof(textKeyChain) / sizeof(int)); i++)
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{
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numberBuffer = i;
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//CHECK, IF numberBuffer ISN'T GREATER THAN KEY_LENGTH AND CUT UNUSED LENGTH
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while (numberBuffer >= KEY_LENGTH)
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{
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numberBuffer -= KEY_LENGTH;
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}
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//FILL textKeyChain
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if ((numberBuffer + 1) % 3 == 0)
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{
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textKeyChain[i] = key[numberBuffer] * key[numberBuffer + 1];
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} else if ((numberBuffer + 1) % 2 == 0)
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{
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textKeyChain[i] = key[numberBuffer] - key[numberBuffer + 1];
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} else
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{
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textKeyChain[i] = key[numberBuffer] + key[numberBuffer + 1];
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}
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}
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//LOAD encryptedTextKeyChain
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for (int i = 0; i < (sizeof(encryptedTextKeyChain) / sizeof(int)); i++)
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{
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numberBuffer = 0;
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//GET LENGTH OF EACH CHARACTER
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for (int j = 0; j < strlen(text); j++)
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{
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if (text[j] == ENCRYPTION_SEPARATOR) break;
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numberBuffer++;
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}
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textBuffer = malloc(numberBuffer);
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//LOAD textBuffer
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for (int j = 0; j < strlen(text); j++)
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{
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textBuffer[j] = text[j];
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if (numberBuffer == j) break;
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}
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encryptedTextKeyChain[i] = atoi(textBuffer);
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text += numberBuffer + 1;
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free(textBuffer);
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}
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//DECRYPT TEXT
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for (int i = 0; i < (sizeof(textKeyChain) / sizeof(int)); i++)
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{
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textKeyChain[i] -= encryptedTextKeyChain[i];
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}
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//LOAD returningText
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for (int i = 0; i < sizeof(textKeyChain) / sizeof(int); i++)
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{
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returningText[i] = (char) textKeyChain[i];
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}
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return returningText;
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}
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