Displaying Secret Data in Binary Format (Rust Code)

In this article, we will explore how to format and display byte data in Rust. Specifically, we’ll focus on a simple program that formats a secret (a Vec<u8>, or vector of bytes) as a binary string.

Understanding the Code

Here is the Rust code that we will break down:

use std::fmt;

struct DisplaySecret {
    secret: Vec<u8>,
}

impl fmt::Display for DisplaySecret {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        for byte in &self.secret {
            write!(f, "{:08b}", byte)?; // Format each byte as binary
        }
        Ok(())
    }
}

fn main() {
    let secret = DisplaySecret {
        secret: vec![255, 34, 100, 9], // Example byte data
    };
    
    println!("{}", secret); // Prints: 11111111100000100011001000001001
}

1. Defining the Struct

struct DisplaySecret {
    secret: Vec<u8>,
}

In this program, we define a structure DisplaySecret with a single field secret which is a Vec<u8>. This field will hold the secret data we want to display. The Vec<u8> is simply a dynamic array of bytes, and it’s a common way to represent binary data in Rust.

2. Implementing fmt::Display for Custom Output

impl fmt::Display for DisplaySecret {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        for byte in &self.secret {
            write!(f, "{:08b}", byte)?; // Format each byte as binary
        }
        Ok(())
    }
}

In Rust, you can implement the fmt::Display trait to control how your custom types are displayed when using println! or format!. Here, we implement this trait for DisplaySecret.

• The fmt::Display trait allows us to define how to format the structure as a string.
• The write!(f, "{:08b}", byte) statement inside the loop formats each byte in the secret vector as an 8-bit binary string ({:08b} specifies binary format with zero-padding to ensure each byte is represented as exactly 8 bits).
• The result is that each byte is printed as a string of 0s and 1s.

3. The main Function

fn main() {
    let secret = DisplaySecret {
        secret: vec![255, 34, 100, 9], // Example byte data
    };
    
    println!("{}", secret); // Prints: 11111111100000100011001000001001
}

In the main function:

• We create an instance of DisplaySecret, initializing it with some byte data (vec![255, 34, 100, 9]).
• println!("{}", secret) is used to display the secret. Since we’ve implemented the fmt::Display trait for DisplaySecret, this triggers the fmt function we defined earlier.

When we run the program, the bytes are printed in their binary representation as follows:

11111111100000100011001000001001

This output corresponds to the binary representation of the bytes 255, 34, 100, and 9 in sequence.

4. Conclusion

In this article, we’ve learned how to format and display byte data as binary strings in Rust by implementing the fmt::Display trait. This allows for more readable and customized output, making it easier to understand and work with raw byte data in your programs.

Key Takeaways:

• fmt::Display is the trait we use to control how types are displayed in Rust.
• We can format byte data using binary representations with {} and the :08b format specifier.
• Using custom formatting like this is particularly useful when working with low-level data, such as cryptographic secrets or network data.

This simple example demonstrates how flexible Rust’s formatting tools can be for presenting data in various ways.

Bonus

This shows the hex version…

{:02x} specifies that the byte should be displayed in hexadecimal (x), and padded with zeros if necessary to ensure two characters (02).

use std::fmt;

struct DisplaySecret {
    secret: Vec<u8>,
}

impl fmt::Display for DisplaySecret {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        for byte in &self.secret {
            write!(f, "{:02x}", byte)?; // Format each byte as hexadecimal
        }
        Ok(())
    }
}

fn main() {
    let secret = DisplaySecret {
        secret: vec![255, 34, 100, 9], // Example byte data
    };
    
    println!("{}", secret); // Prints: ff226409
}