Problem with the out put of the ecc_decryption_key using libtomcrypt in C

Question

I Have the following simple code.

Im just initializing the parameters, calling a make_key function, encrypting the data and trying to decrypted the data

#define LTM_DESC 
#include <tomcrypt.h>
int main(void)
{
    ecc_key mykey;
    prng_state prng;
    int err, prng_idx , hash_idx;

    ltc_mp = ltm_desc;

    /* register yarrow */
    if (register_prng(&yarrow_desc) == -1) {
    printf("Error registering Yarrow\n");
    return -1;
    }
    
    if (register_hash(&sha1_desc) == -1) {
        printf("Error registering sha1");
        return EXIT_FAILURE;
    }

    prng_idx = find_prng("yarrow");
    hash_idx = find_hash("sha1");
    /* setup the PRNG */
    if ((err = rng_make_prng(128, find_prng("yarrow"), &prng, NULL))
    != CRYPT_OK) {
    printf("Error setting up PRNG, %s\n", error_to_string(err));
    return -1;
    }
    /* make a 192-bit ECC key */
    if ((err = ecc_make_key(&prng, find_prng("yarrow"), 55, &mykey))
        != CRYPT_OK) {
        printf("Error making key: %s\n", error_to_string(err));
    return -1;
    }

        const unsigned char *plaintext = (const unsigned char *)"Hello, this is a secret message!";
        unsigned long ptlen = sizeof(plaintext);
        unsigned char ciphertext[1024];
        unsigned long ctlen = sizeof(ciphertext);

    if ((err = ecc_encrypt_key(plaintext,                       // const unsinged char *in
                                    ptlen,                             //unsinged long inlen
                                    ciphertext,                       // unsinged *out
                                    &ctlen,                           // unsinged long *outlen
                                    &prng,                               // prng_state *prng
                                    prng_idx,                         // int wprng
                                    hash_idx,                         // int hash
                                    &mykey)) != CRYPT_OK) {           // ecc_key *ley
            printf("Erro ao criptografar o texto: %s\n", error_to_string(err));
            return -1;
}

printf("Text after encrypted: ");
    for (unsigned long i = 0; i < ctlen; ++i) {
        printf("%02x", ciphertext[i]);
    }
    printf("\n");

    unsigned char decryptedtext[2048];
    unsigned long decrypted_len = sizeof(decryptedtext);
    if ((err = ecc_decrypt_key(ciphertext, ctlen, decryptedtext, &decrypted_len, &mykey)) != CRYPT_OK) {
        printf("Erro ao descriptografar o texto: %s\n", error_to_string(err));
        return -1;
    }

    decryptedtext[decrypted_len] = '\0';

    printf("%d",decryptedtext == plaintext);
    printf("\n");
    printf("Text after decrypted: %.*s\n", (int)decrypted_len, decryptedtext);
    printf("Text after decrypted: %s\n", plaintext);

    printf("Text after decryptedo: ");
    for (unsigned long i = 0; i < decrypted_len; ++i) {
        printf("%c", decryptedtext[i]);
    }
    printf("\n");

    // Update decrypted_len based on the actual length of the decrypted text
decrypted_len = strlen((char *)decryptedtext);

// Print the decrypted text
printf("Text after decrypted: %s\n", decryptedtext);

printf("Text after decrypted (Hex): ");
for (unsigned long i = 0; i < decrypted_len; ++i) {
    printf("%02x", decryptedtext[i]);
}
printf("\n");


return 0;
}

in my terminal im compiling using

gcc -Wall -O0 -g test2.c -ltomcrypt -o test2

I'd like to see after the line

printf("Text after decrypted: %s\n", decryptedtext);

Text decrypted: Hello, this is a secret message!

but I'm seeing

Text decrypted: Hello, t

Why the print isnt complete? I dont know what to do to see the complete mensage decrypted.

** NEWS

I got news, apparently, doesnt matter the variable 'decrypted_len' after i call the function ecc_decrypted_key it will be set in 8.

What can I do?

Answer 1

This code

const unsigned char *plaintext = (const unsigned char *)"Hello, this is a secret message!";
unsigned long ptlen = sizeof(plaintext);

Sets ptlen to the size of the pointer plaintext.

This code will be better

const unsigned char plaintext[] = "Hello, this is a secret message!";
unsigned long ptlen = sizeof(plaintext);

But that would still be subject to the length limitations of ECC encryption.