Ndtyjky

Hello I was studying aes 128 encryption with this link https://www.gurutechnologies.net/blog/aes-ctr-encryption-in-c/.
But to run the example main.c
Compiled as follows

gcc main.c -lm -lcrypto -lssl -o mai.c

Then I get the following error:

main.c: In function ‘fencrypt’:

main.c:83:3: warning: implicit declaration of function ‘AES_ctr128_encrypt’; did you mean ‘AES_cfb128_encrypt’? [-Wimplicit-function-declaration]

   AES_ctr128_encrypt(indata, outdata, bytes_read, &key, state.ivec, state.ecount, &state.num);

   ^~~~~~~~~~~~~~~~~~

   AES_cfb128_encrypt

/tmp/cc1Gq6eV.o: In function `fencrypt':

main.c:(.text+0x253): undefined reference to `AES_ctr128_encrypt'

/tmp/cc1Gq6eV.o: In function `fdecrypt':

main.c:(.text+0x449): undefined reference to `AES_ctr128_encrypt'

collect2: error: ld returned 1 exit status

To fix this I go into the directory where openssl is located, and in the aes.h header file
I tried to find the AES_ctr128_encrypt function, but it did not
So I updated the openssl and confirmed that there is a AES_ctr128_encrypt function in aes.h and tried to recompile it, but nothing changed. I will leave a question because I could not find a solution anymore.

This is the code for AES_ctr128_encrypt

void fencrypt(char* read, char* write, const unsigned char* enc_key)

{ 

    if(!RAND_bytes(iv, AES_BLOCK_SIZE))

    {

        fprintf(stderr, "Could not create random bytes.");

        exit(1);    

    }



    readFile = fopen(read,"rb"); // The b is required in windows.

    writeFile = fopen(write,"wb");



    if(readFile==NULL)  

    {

        fprintf(stderr, "Read file is null."); 

        exit(1);

    }



    if(writeFile==NULL)

    {

        fprintf(stderr, "Write file is null."); 

        exit(1);

    }



    fwrite(iv, 1, 8, writeFile); // IV bytes 1 - 8

    fwrite("", 1, 8, writeFile); // Fill the last 4 with null bytes 9 - 16



    //Initializing the encryption KEY

    if (AES_set_encrypt_key(enc_key, 128, &key) < 0)

    {

        fprintf(stderr, "Could not set encryption key.");

        exit(1); 

    }



    init_ctr(&state, iv); //Counter call

    //Encrypting Blocks of 16 bytes and writing the output.txt with ciphertext  

    while(1)    

    {

        bytes_read = fread(indata, 1, AES_BLOCK_SIZE, readFile); 

        AES_ctr128_encrypt(indata, outdata, bytes_read, &key, state.ivec, state.ecount, &state.num);



        bytes_written = fwrite(outdata, 1, bytes_read, writeFile); 

        if (bytes_read < AES_BLOCK_SIZE)

        {

            break;

        }

    }



    fclose(writeFile);

    fclose(readFile);

}



void fdecrypt(char* read, char* write, const unsigned char* enc_key)

{   



    readFile=fopen(read,"rb"); // The b is required in windows.

    writeFile=fopen(write,"wb");



    if(readFile==NULL)

    {

        fprintf(stderr,"Read file is null."); 

        exit(1);

    }



    if(writeFile==NULL) 

    {

        fprintf(stderr, "Write file is null."); 

        exit(1);

    }



    fread(iv, 1, AES_BLOCK_SIZE, readFile); 



    //Initializing the encryption KEY

    if (AES_set_encrypt_key(enc_key, 128, &key) < 0)

    {

        fprintf(stderr, "Could not set decryption key.");

        exit(1);

    }



    init_ctr(&state, iv);//Counter call

    //Encrypting Blocks of 16 bytes and writing the output.txt with ciphertext       

    while(1)    

    {

        bytes_read = fread(indata, 1, AES_BLOCK_SIZE, readFile);    

        //printf("%in", state.num);

        AES_ctr128_encrypt(indata, outdata, bytes_read, &key, state.ivec, state.ecount, &state.num);



        bytes_written = fwrite(outdata, 1, bytes_read, writeFile); 

        if (bytes_read < AES_BLOCK_SIZE) 

        {

            break;

        }

    }

    fclose(writeFile); 

    fclose(readFile); 

}

Thank you in advance.

Assuming you are using openssl 1.1.0, see What is exact alternate API instead of AES_ctr128_encrypt from openssl 1.1.0?

You can use CRYPTO_ctr128_encrypt instead of AES_ctr128_encrypt.