To kick things off, let’s define our terms. A hash function takes an input (like a file or some text) and produces a fixed-size output that represents that input in a unique way. This output is called the hash value or message digest. The idea behind using hash functions is to make it easy to compare two inputs without having to store their entire contents, which can be useful for things like checking if files have been modified or verifying digital signatures.
Now Blake2s specifically. It’s a cryptographic hash function that was designed by Jean-Philippe Aumasson and his team in 2012 as part of the SHA-3 competition. The “s” stands for “streaming,” which means it can handle data in chunks instead of requiring you to load everything into memory at once. This makes it a great choice for situations where you have large amounts of data that need to be hashed quickly and efficiently.
So, how do we implement Blake2s in C? Well, first we’ll need to include the necessary header files:
// This script demonstrates how to implement Blake2s in C, a popular hash function that is efficient for handling large amounts of data.
// First, we need to include the necessary header files. This allows us to access the functions and data types defined in these files.
#include <stdio.h> // This is the standard input/output library, which provides functions for reading and writing data.
#include "blake2s.h" // This is the header file for Blake2s, which contains the necessary functions and data types for implementing the hash function.
// Next, we can define our main function, which is the entry point for our program.
int main() {
// We can declare variables to store our data and the resulting hash.
char data[] = "This is some data to be hashed."; // This is a character array that holds the data we want to hash.
char hash[32]; // This is a character array that will store the resulting hash, which is 32 bytes long.
// Now, we can call the blake2s function to hash our data. We pass in the data, the length of the data, the hash array, and the length of the hash.
blake2s(data, sizeof(data), hash, sizeof(hash));
// Finally, we can print out the resulting hash.
printf("The hash of the data is: ");
for (int i = 0; i < sizeof(hash); i++) { // This loop iterates through each byte of the hash and prints it out in hexadecimal format.
printf("%02x", hash[i]);
}
printf("\n");
return 0; // This ends the main function and returns 0, indicating successful execution.
}
// Overall, this script demonstrates how to use the blake2s function to hash data and print out the resulting hash.
The `blake2s.h` file contains the definition of our hash function and some helper functions that make it easier to use. Next, we’ll define a simple function that takes an input string (or any other data) and returns its Blake2s hash value:
// This script calculates the Blake2s hash value of an input string or data.
#include "blake2s.h" // Include the header file containing the hash function and helper functions.
// Define a function that takes an input string and its length as parameters and returns the hash value.
uint8_t blake2s_hash(const char *input, size_t len) {
uint8_t out[BLAKE2S_DIGEST_LENGTH]; // Create an output buffer to store the hash value.
const unsigned int keylen = 0; // Set the length of the secret key to 0.
const void *key = NULL; // Set the secret key to NULL.
blake2s(out, BLAKE2S_DIGEST_LENGTH, key, keylen, (const uint8_t *)input, len); // Call the blake2s function to calculate the hash value.
return out[BLAKE2S_DIGEST_LENGTH - 1]; // Return the last byte of the hash value, which serves as the checksum.
}
This function takes two arguments: `input` and `len`. The first argument is a pointer to our input data (in this case, we’re using a string), and the second argument is the length of that data. We then declare an output buffer called `out`, which will hold the resulting hash value.
The next three arguments are optional: `key` is a secret key for encrypting or decrypting our input (we’ll ignore this for now since we don’t need it), and `keylen` specifies the length of that key if we have one. Finally, we call the actual hash function using the `blake2s()` macro provided by the header file.
The last line returns the final byte of our hash value, which is used as a checksum to ensure that the hash was computed correctly. If you’re curious about how this works, feel free to read up on the Blake2s specification or ask me in the comments below!
It may not be as exciting as a roller coaster ride, but it’s definitely more useful for your computer science projects.