Fundamentals of Blockchain Technology in C Language: Hashing and Encryption

Blockchain technology has garnered significant attention in recent years, with its core focus on data security and immutability. In blockchain, hash functions and encryption algorithms play crucial roles. This article will introduce how to implement basic hashing and encryption functions in C language to help beginners understand these concepts.

1. Introduction to Hash Functions

A hash function is an algorithm that converts input data (commonly referred to as a “message”) into a fixed-length string (known as a “hash value” or “digest”). It has the following characteristics:

  • Deterministic: The same input always produces the same output.
  • Fast Computation: It can quickly compute the hash value for any given data.
  • Collision Resistance: It is difficult to find two different inputs that produce the same output.
  • Irreversibility: The original data cannot be inferred from the hash value.

1.1 Implementing Simple Hashing with SHA256

In C language, we can use the OpenSSL library to implement the SHA256 algorithm. First, ensure that you have installed the OpenSSL library.

Below is a simple example demonstrating how to generate the hash value of a string using SHA256:

#include <stdio.h>
#include <string.h>
#include <openssl/sha.h>
void calculate_sha256(const char *str, unsigned char outputBuffer[SHA256_DIGEST_LENGTH]) {
    SHA256((unsigned char*)str, strlen(str), outputBuffer);
}
int main() {
    const char *input = "Hello, Blockchain!";
    unsigned char hash[SHA256_DIGEST_LENGTH];
    calculate_sha256(input, hash);
    printf("Input: %s\n", input);
    printf("SHA256 Hash: ");
    for(int i = 0; i < SHA256_DIGEST_LENGTH; i++) {
        printf("%02x", hash[i]);
    }
    printf("\n");
    return 0;
}

Code Explanation

  1. Include the necessary header files, including <span><openssl/sha.h></span> to use SHA-related functions.
  2. Define the <span>calculate_sha256</span> function, which takes a string and returns its corresponding SHA-256 hash value.
  3. In the <span>main</span> function, we define the string to be hashed and call the above function to generate its hash value, then print it in hexadecimal format.

2. Introduction to Encryption

Encryption is a method of protecting information by converting plaintext into information that can only be interpreted by authorized users (i.e., ciphertext). Common symmetric encryption algorithms include AES, DES, etc., while asymmetric encryption includes RSA, etc.

2.1 Symmetric Encryption Using AES

We can utilize the AES functionality in the OpenSSL library to implement simple data encryption and decryption. The following example demonstrates basic operations using AES:

#include <stdio.h>
#include <string.h>
#include <openssl/aes.h>
void aes_encrypt(const unsigned char *key, const unsigned char *data, unsigned char *encrypted) {
    AES_KEY encryptKey;
    // Set 128-bit AES key
    AES_set_encrypt_key(key, 128, &encryptKey);
    // Perform AES encryption
    AES_encrypt(data, encrypted, &encryptKey);
}
int main() {
   // Plaintext and key must both be 16 bytes long
   unsigned char key[AES_BLOCK_SIZE] = "0123456789abcdef";
   unsigned char data[AES_BLOCK_SIZE] = "Hello World!!!";
   unsigned char encrypted[AES_BLOCK_SIZE];
   aes_encrypt(key, data, encrypted);
   printf("Encrypted text: ");
   for(int i = 0; i < AES_BLOCK_SIZE; i++) {
       printf("%02x", encrypted[i]);
   }
   printf("\n");
   return 0;
}

Code Explanation

  1. Include the necessary header files, including <span><openssl/aes.h></span> to use AES-related functions.
  2. Define the <span>aes_encrypt</span> function, which takes a key, plaintext data, and a location to store the result as parameters, and performs AES encryption.
  3. In the <span>main</span> function, we define a 16-byte long plaintext and key, call the <span>aes_encrypt</span> function for processing, and then print the result in hexadecimal format.

Conclusion

This article introduced a part of the fundamentals of blockchain technology in C language, specifically implementing basic hashing and symmetric encryption using the OpenSSL library. These techniques are crucial for building secure and reliable data structures. In practical applications, you may need more complex data structures and additional security measures, but mastering these foundational concepts is undoubtedly an important step towards deeper learning. I hope this article helps you better understand the core concepts behind blockchain!

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