Ethereum: Byte Array to Hexadecimal and Back Again in JavaScript [closed]

Converting a Byte Array to Hexadecimal and Back Again in JavaScript

In this article, we’ll explore how to take a byte array generated using the Web Crypto API and convert it back into hexadecimal format.

Generating a Random Byte Array

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We start by generating a random byte array of 16 elements using window.crypto.getRandomValues(new Uint8Array(16)). This method uses the browser’s random number generator to fill the Uint8Array with random values.

var myByteArray = window.crypto.getRandomValues(new Uint8Array(16));

Converting the Byte Array to Hexadecimal

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To convert a byte array to hexadecimal, we can use the toString() method with the radix parameter set to 16 (hexadecimal). We’ll also need to specify the type of number to use when representing each byte value. Here’s how you can do it:

myByteArray.forEach(function(byte) {

    var hex = byte.toString(16).padStart(2, '0');

    console.log(hex);

});

In this example, we’re iterating over each element in the myByteArray and converting its binary representation to a hexadecimal string. We use padStart(2, '0') to ensure that each hexadecimal value has exactly 2 characters.

Converting Hexadecimal Back to Byte Array

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To convert a hexadecimal string back into a byte array, we can use the parseInt() method with base 16 and then create a new Uint8Array. We’ll also need to pad the resulting values with zeros if necessary.

var hexString = '18114316136';

var byteArray = new Uint8Array(hexString.length);

for (var i = 0; i < hexString.length; i++) {

    var value = parseInt(hexString[i], 16);

    if ((value & 0x80) !== 0) {

        // Carry the 8 bits to the next position

        byteArray[i] = 0xFF | value & 0x7F;

    } else {

        // Don't carry; just append the byte value

        byteArray[i] = value;

    }

}

console.log(byteArray);

In this example, we’re converting a hexadecimal string to a Uint8Array. We use parseInt() with base 16 and then check for any carries (i.e., values greater than or equal to 128). If there’s a carry, we set the corresponding byte value in the byteArray. Otherwise, we simply append the original value.

Example Use Cases

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Here are some example use cases for this code:

• Converting random numbers generated by a Web Crypto API (e.g., crypto.getRandomValues()) to hexadecimal and back into a Uint8Array.

• Using the resulting byte array as input for a cryptographic algorithm or data processing task.

By following these steps, you can efficiently convert between a byte array and hexadecimal format in JavaScript using the Web Crypto API.

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