MQTTs client with Post-Quantum TLS Using mbedtls

The project is meant to showcase the Hybrid Post-Quantum capabilities of an MQTTs client using TLS 1.3 and the mbedtls library.
For info or comments, contact us at hello@securitypattern.com

mbedtls

Introduction of Hybrid Post-Quantum cryptography

The TLS handshake has been agumented with Hybrid PQ capabilities by introducing a new KEM and a new signature mechanism.
These are, respectively X25519-MLKEM768 and Ed25519-MLDSA.

The functions responsible for the KEM can be found in qubip.c:

HybridKeyKEM *hybrid_key_gen();
void hybrid_key_free(HybridKeyKEM *);

The signature and signature verification functions are implemented in the already present mbedtls file pk_wrap.c that get called several times during the TLS handshake.

static int ed25519_mlds44_sign_wrap(mbedtls_pk_context *pk,
		mbedtls_md_type_t md_alg, const unsigned char *hash, size_t hash_len,
		unsigned char *sig, size_t sig_size, size_t *sig_len,
		int (*f_rng)(void*, unsigned char*, size_t), void *p_rng);

static int ed25519_mlds44_verify_wrap(mbedtls_pk_context *pk,
		mbedtls_md_type_t md_alg, const unsigned char *hash, size_t hash_len,
		const unsigned char *sig, size_t sig_len);

Furthermore, the certificate parsing functionalities have been expanded to include support for Hybrid PQ certificates in file pk_parse.c

A few examples of Hybrid PQ certificates have been hardcoded in file MQTTInterface.c

The ID definitions for the Hybrid mechanism are as follows:

#define MBEDTLS_SSL_IANA_TLS_GROUP_MLKEM768 0x11ec
#define MBEDTLS_TLS1_3_SIG_ED25519_MLDSA44 0x090a
#define MBEDTLS_TLS1_3_SIG_ED25519_MLDSA65 0x090b

as shown in file ssl.h