Simple Vernam Encryption C Snippet

vernam.c

/** Algorithme de cryptage Vernam
*** Grabriel Lemieux
***
**/

#include <stdio.h>
#include <string.h>
#include <unistd.h>


typedef unsigned int uint;
uint flags;

void printv(const char toPrint[]);
uint verbose();
uint encode(char toEncode[]);
uint decode(char toDecode[]);
int getFileSize(FILE *toGet);

int main(int args,char* argv[]){
	flags=0;
	int opt=0;

	while(opt != -1){
		opt = getopt(args,argv,"cdv");
		switch(opt){
			case 'c':
				flags|=0x01;
				printf("As it's use user generated entropy, the encryption will take some time.\n'");
				break;
			case 'd':
				flags|=0x02;
				break;
			case 'v':
				flags|=0x04;
				printf("Vernam V 0.1 -- Verbose Mode --\n");
				break;
			case 'h':
				break;						
		}

	}
	
	if( (flags & 0x02) && (flags & 0x01)){
		printf("Cannot do the both in same time!\n");
		return -1;
	}

	if(flags & 0x01){
			int i=0;
			for(i=optind;i<args;++i){
				if(verbose()){
					printf("Encoding file: %s \n ",argv[i]);
				}
				encode(argv[i]);
			}
	}

	if(flags & 0x02){
			int i=0;
			for(i=optind;i<args;++i){
				if(verbose()){
					printf("Decoding file: %s \n",argv[i]);
				}
				decode(argv[i]);
			}

	}
	
	return 0;
}


void printv(const char toPrint[]){
	if(flags & 0x04){
		printf("%s\n",toPrint);	
	}
}

uint verbose(){
	return (flags & 0x04)?1:0;
}

uint encode(char toEncode[]){

	//Le fichier à lire et le fichier à encoder
	FILE* fichier = fopen(toEncode,"r");
	FILE* random = fopen("/dev/random","r");

	if(fichier == NULL){
		printf("File %s not found.");
		return 0;	
	}	

	//Connaitre la taille du fichier
	fseek(fichier,0,SEEK_END);
	int size = ftell(fichier);
	rewind(fichier);

	
	printv("\tLoading file in memory.");
	char encoded[size];
	char key[size];

	//Charger la clef en mémoire
	int i;
	for(i=0;i<size;i++){
		fread(&(key[i]),sizeof(char),1,random);
	}

	//Fermer le fichier random, le chargement est terminé
	fclose(random);

	printv("\tCoding the file:");

	//Appliquer la clef
	for(i=0;i<size;i++){
		char temp;		
		fread(&temp,sizeof(char),1,fichier);
		encoded[i] = temp ^ key[i];
		if(verbose()){
			printf("%c ^ %c (%c)",temp,key[i],encoded[i]);		
		}		
	}

	printv(" ");		
	printv("\tSaving encoded file.");

	//Éviter les attaques en assignant la bonne valeur à "toSavePath"
	int strlengtin = strlen(toEncode) + strlen(".enc") ;
	char toSavePath[strlengtin];
	char toSaveKPath[strlengtin];
	
	strcpy(toSavePath,toEncode);
	strcat(toSavePath,".enc");

	strcpy(toSaveKPath,toEncode);
	strcat(toSaveKPath,".key");
	
	//Sauvegarder le fichier
	FILE* toSave = fopen(toSavePath,"w");
	FILE* toSaveKey = fopen(toSaveKPath,"w");

	for(i=0;i<size;++i){
		fwrite(&(encoded[i]),sizeof(char),1,toSave);
		fwrite(&(key[i]),sizeof(char),1,toSaveKey);
	}

	fclose(toSave);
	fclose(toSaveKey);
		
	return 1;
}

uint decode(char toDecode[]){
	//Éviter les attaques en assignant la bonne valeur "toGetPath"
	int strlengtin = strlen(toDecode) + strlen(".enc");
	char toGetPath[strlengtin];
	char toGetKPath[strlengtin];

	strcpy(toGetPath,toDecode);
	strcat(toGetPath,".enc");

	strcpy(toGetKPath,toDecode);
	strcat(toGetKPath,".key");

	printv("\tOpenning key and source file.");
	
	FILE* inEncode = fopen(toGetPath,"r");
	FILE* inKeyCode= fopen(toGetKPath,"r");

	if( (inEncode==NULL) && (inKeyCode==NULL) ){
		printf("\tFile %s or %s not found.\n",inEncode,inKeyCode);
		return 0;	
	}

	int sizeC = getFileSize(inEncode);
	int sizeD = getFileSize(inKeyCode);

	if( sizeC != sizeD ){
		printf("\tThe size doesn't fit.\n");		
		return 0;
	}	

	printv("\tReading files.");
	char decoded[sizeC];
	int i;
	for(i=0;i<sizeC;++i){
		char tempKey;	
		char tempCoded;	
		fread(&(tempKey),sizeof(char),1,inKeyCode);
		fread(&(tempCoded),sizeof(char),1,inEncode);
		decoded[i]= tempKey ^ tempCoded;
		if(verbose()){
			printf("%c ^ %c (%c)",tempCoded,tempKey,decoded[i]);		
		}
	}

	fclose(inEncode);
	fclose(inKeyCode);
	FILE* decodedFile = fopen(toDecode,"w");
	
	printv("\tWritting of the coded file.");
	for(i=0;i<sizeC;++i){
		fwrite(&(decoded[i]),sizeof(char),1,decodedFile);
	}

	fclose(decodedFile);
	return 1;
}

int getFileSize(FILE *toGet){
	fseek(toGet,0,SEEK_END);
	int size = ftell(toGet);	
	rewind(toGet);	
	
	return size;

}