AES-256 ECB Encryption Implementation in C

This repository showcases a concise implementation of the AES-256 ECB (Electronic Codebook) encryption algorithm in C, renowned for its heightened security.

Features

• AES-256 ECB: Implements secure AES-256 ECB encryption mode.
• Fixed Block Size: Enforces a 16-byte fixed block size without padding.
• Compatibility: Encrypted data is interoperable with any AES-256 ECB decryption.

Usage

Include "AES_256_ECB.h" before using AES-256 ECB functions.

#include "AES_256_ECB.h"

AES Context Initialization

AES_CTX ctx;

Function: AES_EncryptInit

Initialize the AES context for encryption.

void AES_EncryptInit(AES_CTX *ctx, const unsigned char *key);

• ctx: AES context structure.
• key: Encryption key (32 bytes for AES-256).

Function: AES_Encrypt

Encrypt a single 16-byte block of data.

void AES_Encrypt(AES_CTX *ctx, const unsigned char *plaintext, unsigned char *ciphertext);

• ctx: AES context structure.
• plaintext: Input plaintext block (16 bytes).
• ciphertext: Output encrypted block (16 bytes).

For multiple blocks, use a loop:

for (unsigned int offset = 0; offset < multiple_block_size; offset += AES_BLOCK_SIZE) {
    AES_Encrypt(&ctx, plaintext + offset, ciphertext + offset);
}

Function: AES_DecryptInit

Initialize the AES context for decryption.

void AES_DecryptInit(AES_CTX *ctx, const unsigned char *key);

• ctx: AES context structure.
• key: Decryption key (32 bytes for AES-256).

Function: AES_Decrypt

Decrypt a single 16-byte block of data.

void AES_Decrypt(AES_CTX *ctx, const unsigned char *ciphertext, unsigned char *plaintext);

• ctx: AES context structure.
• ciphertext: Input encrypted block (16 bytes).
• plaintext: Output decrypted block (16 bytes).

For multiple blocks, use a loop:

for (unsigned int offset = 0; offset < multiple_block_size; offset += AES_BLOCK_SIZE) {
    AES_Decrypt(&ctx, ciphertext + offset, plaintext + offset);
}

Function: AES_CTX_Free

Free resources associated with the AES context.

void AES_CTX_Free(AES_CTX *ctx);

• ctx: AES context structure.

Example Code (main.c)

#include <stdio.h>
#include "AES_256_ECB.h"

void output(const char *title, const unsigned char *data, unsigned int size) {
    printf("%s", title);
    for (unsigned int index = 0; index < size; index++) {
        printf("%02X", data[index]);
    }
    printf("\n");
}

int main() {
    AES_CTX ctx;
    unsigned char key[AES_KEY_SIZE];
    unsigned char data[AES_BLOCK_SIZE];
    
    // Initialization and usage example
    memset(key, 0x79, AES_KEY_SIZE);
    memset(data, 0x79, AES_BLOCK_SIZE);
    
    output("Original: 0x", data, 16);
    
    AES_EncryptInit(&ctx, key);
    AES_Encrypt(&ctx, data, data);
    
    output("\nEncrypted: 0x", data, 16);
    
    AES_DecryptInit(&ctx, key);
    AES_Decrypt(&ctx, data, data);
    
    output("\nDecrypted: 0x", data, 16);
    
    AES_CTX_Free(&ctx);
    return 0;
}

Contributions

Contributions and feedback are welcome! Open issues or submit pull requests.

License

This AES-256 ECB implementation is provided under the MIT License.

Other AES Implementations

• AES-256 CBC by halloweeks
• AES-128 ECB by halloweeks