Problems with encrypting a file - c

Question

I was trying to encrypt a file from a header file and every time I run the program, it deletes the information in the file AccountInformation.txt. Is there any reason why it is deleting the information from AccountInformation.txt and how can I fix my code?
Any help will be great, thank you.
The c code is bellow:
#include <stdio.h>
#include <string.h>
#include "Encryption1.h"
// Variable for signup and login
char fname[120], lname[120], username[120], password[120];
int session;
FILE * accountInfoPointer;
// Main Fucntion for sign up and login
int main (void)
{
// Asking user is they want to sign up or login
printf("What would you like to do?\n");
printf("1. Sign u\n");
printf("2. Login\n");
printf("3. Admin login");
scanf("%d", &session);
// signup
switch(session)
{
case 1:
// Retreiving all of the user's data
printf("What is your FIRST name?\n");
scanf(" %s", fname);
printf("What is your LAST name?\n");
scanf(" %s", lname);
printf("Please enter a username?\n");
scanf(" %s", username);
printf("Create a password\n");
scanf(" %s", password);
accountInfoPointer = fopen("AccountInformation.txt", "a");
fprintf(accountInfoPointer, "Name: %s %s\nUsername: %s\nPassword: %s\n\n", fname, lname, username, password);
fclose(accountInfoPointer);
goto Encrypt; //goes to calender menu
Encrypt:{
//char Title;{
printf("\n\n\t\t\t\t::::::Encrypt::::::\n");
encrypted1(1);
}
break;
}
}
This is the header file code:
#include<stdio.h>
#include<stdlib.h>
int encrypt(void);
int decrypt(void);
int encrypt_view(void);
int decrypt_view(void);
FILE *fp1, *fp2;
char ch;
void encrypted1(int Encrypt)
{
int choice;
while(1)
{
printf("Select One of the Following:\n");
printf("\n1. Encrypt\n");
printf("2. Decrypt\n");
printf("3. View The Encypted File\n");
printf("4. View The Decrypted File\n");
printf("5. Exit\n");
printf("\nEnter Your Choice:\t");
scanf("%d", &choice);
switch(choice)
{
case 1: encrypt();
break;
case 2: decrypt();
break;
case 3: encrypt_view();
break;
case 4: decrypt_view();
break;
case 5: exit(1);
}
}
printf("\n");
// return 0;
}
int encrypt()
{
printf("\n");
fp1 = fopen("AccountInformation.txt","r");
if(fp1 == NULL)
{
printf("Source File Could Not Be Found\n");
}
fp2 = fopen("AccountInformation.txt","w");
if(fp2 == NULL)
{
printf("Target File Could Not Be Found\n");
}
while(1)
{
ch = fgetc(fp1);
if(ch == EOF)
{
printf("\nEnd Of File\n");
break;
}
else
{
ch = ch - (8 * 5 - 3);
fputc(ch, fp2);
}
}
fclose(fp1);
fclose(fp2);
printf("\n");
//return 0;
}
int decrypt()
{
printf("\n");
fp1 = fopen("AccountInformation.txt","r");
if(fp1 == NULL)
{
printf("Source File Could Not Be Found\n");
}
fp2 = fopen("AccountInformation.txt","w");
if(fp2 == NULL)
{
printf("Target File Could Not Be Found\n");
}
while(1)
{
ch = fgetc(fp1);
if(ch == EOF)
{
printf("\nEnd Of File\n");
break;
}
else
{
ch = ch + (8 * 5 - 3);
fputc(ch, fp2);
}
}
fclose(fp1);
fclose(fp2);
printf("\n");
//return 0;
}
int encrypt_view()
{
printf("\n");
fp1 = fopen("AccountInformation.txt","r");
if(fp1 == NULL)
{
printf("No File Found\n");
exit(1);
}
else
{
while(1)
{
ch = fgetc(fp1);
if(ch == EOF)
{
break;
}
else
{
printf("%c", ch);
}
}
printf("\n");
fclose(fp1);
}
printf("\n");
//return 0;
}
int decrypt_view()
{
printf("\n");
fp1 = fopen("AccountInformation.txt","r");
if(fp1 == NULL)
{
printf("No File Found\n");
exit(1);
}
else
{
while(1)
{
ch = fgetc(fp1);
if(ch == EOF)
{
break;
}
else
{
printf("%c", ch);
}
}
printf("\n");
fclose(fp1);
}
// return 0;
printf("\n");
}

Answer 1

fp1 = fopen("AccountInformation.txt","r");
if(fp1 == NULL)
{
printf("Source File Could Not Be Found\n");
}
fp2 = fopen("AccountInformation.txt","w");
if(fp2 == NULL)
{
printf("Target File Could Not Be Found\n");
}
I cringe at this, but the idea should work on unix derivatives. You're clobbering your data because you should have used "r+" but you used "w". The + turns on both read and write, but w+ is going to truncate. You don't want a. Unless you're writing a log file, you don't want a so don't try it here.

Answer 2

At least this problem:
Unable to distinguish all input from fgetc() properly
char, as 8-bit, can encode 256 combinations. int fgetc() returns 257 values: [0-UCHAR_MAX] and EOF.
Code encrypts with ch = ch - (8 * 5 - 3); fputc(ch, fp2); which easily generates a char that collides with EOF on a later read making the file scant.
char ch; // Bad
ch = fgetc(fp1);
if(ch == EOF) // Was ch an EOF or some character?
Use int ch to distinguish the return values from fgetc().
For encryption/decryption, better to open the files in binary mode than text mode. Append a "b".
// fp1 = fopen("AccountInformation.txt","r");
fp1 = fopen("AccountInformation.txt","rb");
Alternative sample code:
int encrypt_view(void) {
printf("\n");
FILE *fp = fopen("AccountInformation.txt", "rb");
if (fp == NULL) {
printf("No File Found\n");
return 1; // Let calling code exit
}
int ch;
while ((ch = fgetc(fp)) != EOF) {
if (ch >= ' ' && ch <= '~') {
printf("%c", ch);
} else {
printf("<%d>", ch);
}
}
printf("\n");
fclose(fp);
return 0;
}