binary string to textfile

Posted on 2006-11-30
Medium Priority
Last Modified: 2010-04-01
I have a program that encrypts a password. I want to store the encrypted password in a text file. How do I do that? Is there some function I can use to automatically convert it to a text format and then back again?

I  use Visual Studio.
Question by:mdoland
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
LVL 14

Expert Comment

ID: 18048353
Simple way: print the binary password as hexidecimal digits. The length in the disk will be twice as long as in memory because it takes 2 hex digits to write one byte. When you read it back in it is very easy to convert back to binary.

A little tougher: base64-encode the binary password before writing it. The length in the disk file will be about 1/3 longer than the length in memory. base64 encoding and decoding functions are widely available, just google for it.

Easy, but less user-friendly: just write out the binary password as binary data. The down-side is that you won't be able to easily view it in an editor.

Which to choose depends on your needs.
LVL 14

Accepted Solution

wayside earned 500 total points
ID: 18048566
To convert a binary buffer to a string of hex digits:

BYTE password[256];

// fill somehow

char buffer[513] = { 0 };

for (int i=0; i<255; i++) {
   sprintf(&buffer[i], "%x", (password[i] >> 4) & 0x0f);
   sprintf(&buffer[i+1], "%x", password[i] & 0x0f);

To convert back is similar:

byte convert(char hexdigit) {
  if (hexdigit >= '0' || hexdigit <= '9')   return char - '0';
 else if (hexdigit == 'a' || hexdigit == 'A') return 10;
else if (hexdigit == 'b' || hexdigit == 'B') return 11;
else if (hexdigit == 'c' || hexdigit == 'C') return 12;
else if (hexdigit == 'd' || hexdigit == 'D') return 13;
else if (hexdigit == 'e' || hexdigit == 'E') return 14;
else if (hexdigit == 'f' || hexdigit == 'F') return 15;
else return 0;

BYTE password[256] = { 0 };

char buffer[513] = { 0 };
// read the password into the buffer

for (int i=0; i<255; i++) {
   password[i] = convert(buffer[i*2]) << 4 | convert(buffer[i*2+1]);

Author Comment

ID: 18052336
Shouldn't this part:
for (int i=0; i<255; i++) {
   sprintf(&buffer[i], "%x", (password[i] >> 4) & 0x0f);
   sprintf(&buffer[i+1], "%x", password[i] & 0x0f);

be like this:

for (int i=0; i<255; i++) {
   sprintf(&buffer[2*i], "%x", (password[i] >> 4) & 0x0f);
   sprintf(&buffer[2*i+1], "%x", password[i] & 0x0f);
LVL 14

Expert Comment

ID: 18053603
Yep, you are right. That's what happens when you don't test your code before posting it, no matter how simple it looks. :)


Featured Post

Free Tool: SSL Checker

Scans your site and returns information about your SSL implementation and certificate. Helpful for debugging and validating your SSL configuration.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Errors will happen. It is a fact of life for the programmer. How and when errors are detected have a great impact on quality and cost of a product. It is better to detect errors at compile time, when possible and practical. Errors that make their wa…
Written by John Humphreys C++ Threading and the POSIX Library This article will cover the basic information that you need to know in order to make use of the POSIX threading library available for C and C++ on UNIX and most Linux systems.   [s…
The viewer will learn how to use the return statement in functions in C++. The video will also teach the user how to pass data to a function and have the function return data back for further processing.
The viewer will learn how to user default arguments when defining functions. This method of defining functions will be contrasted with the non-default-argument of defining functions.
Suggested Courses
Course of the Month15 days, 11 hours left to enroll

743 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question