im trying to code a Diffie-Hellman key Exchange (client side) into a XMC4500 and I'm using ARMmbed lib.
This is the code I got (based on dh_client.c):
int dhm (void) {
int ret;
size_t n, buflen;
unsigned char *p, *end;
unsigned char buf[512];
unsigned char hash[32];
const char *pers = "dh_client";
mbedtls_entropy_context entropy;
mbedtls_ctr_drbg_context ctr_drbg;
mbedtls_rsa_context rsa;
mbedtls_dhm_context dhm;
mbedtls_aes_context aes;
mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_SHA256 );
mbedtls_dhm_init( &dhm );
mbedtls_aes_init( &aes );
mbedtls_ctr_drbg_init( &ctr_drbg );
/*
* 1. Setup the RNG
*/
mbedtls_entropy_init( &entropy );
ret = mbedtls_ctr_drbg_seed( &ctr_drbg,
mbedtls_entropy_func,
&entropy,
(const unsigned char *) pers,
strlen( pers ) );
mbedtls_aes_free( &aes );
mbedtls_rsa_free( &rsa );
mbedtls_dhm_free( &dhm );
mbedtls_ctr_drbg_free( &ctr_drbg );
mbedtls_entropy_free( &entropy );
return ret;}
I did not try to go further this, because it is not working and it is the very beginning of dhm algorithm. The function mbedtls_ctr_drbg_seed is returning MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED.
Also in the ctr_drbg.h I had to edit the MBEDTLS_CTR_DRBG_MAX_SEED_INPUT from 384(default) to 336, otherwise the code would crash. Everything else is default.
Someone knows why is returning this error? Thanks in advance.
Note: Im calling this function in main. Running the code gives me no errors.
