I’m learning how to use openssl and learn more about it.

I wrote a very short line of codes which AES encrypts plaintext and display the output as ciphered text. I had no idea how to display its encrypted plaintext.

#include <openssl/evp.h>
#include <openssl/rand.h>
#include <openssl/err.h>
#include <stdint.h>

int main()
{
    unsigned char *buf;
    int num;
    int rn = RAND_bytes(buf, num);

    //if(rn != 1)
    //{
    //  ERR_print_errors(bp);   
    //}

    if(rn == 1)
    {
        EVP_CIPHER_CTX *ctx;
        const EVP_CIPHER *type = EVP_aes_128_cbc();
        const unsigned char *iv;
        unsigned char *out;
        int *outl;
        unsigned char *in;
        int inl;
        iv = buf; // Random numbers from RAND_bytes

        const unsigned char *key = (const unsigned char *)
            "x00x01x02x03x04x05x06x07"
            "x08x09x0ax0bx0cx0dx0ex0f"
            "x10x11x12x13x14x15x16x17"
            "x18x19x1ax1bx1cx1dx1ex1f";
        
        in = "password"; // Plaintext to be decrypted
        ctx =  EVP_CIPHER_CTX_new(); // Alocate ctx variable

        EVP_EncryptInit(ctx, type, key, iv);

        EVP_EncryptUpdate(ctx, out, outl, in, inl);
    
        EVP_EncryptFinal(ctx, out, outl);
        
        const char *ciphertext = out;

        uintptr_t ciphertext_len = (uintptr_t)outl; // Convert pointer type variable to non-pointer type variable

        // Bio dump 
        BIO_dump_fp(stdout, out, ciphertext_len);
        // Clean up 
        EVP_CIPHER_CTX_free(ctx);
    }
    
}

I read openssl documentation and from what I’ve understand ‘BIO_dump_fp’ function were used to print out hexadecimal values.