I am using MBEDTLS and most of it works, except I have hit a snag where I am trying to communicate to an https server, and it fails in the ssl->handshake-step (ssl_write_client_key_exchange).

My stack trace shows that it gets to the function ecp_double_jac and never exits. It is looping at

MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &T,  &P->X,  &S      ) ); MOD_ADD( T );.

Stack trace:

test.elf! mbedtls_mpi_sub_abs (mbedtls_mpi * X, const mbedtls_mpi * A, const mbedtls_mpi * B) Line: 1287
  test.elf! ecp_double_jac (const mbedtls_ecp_group * grp, mbedtls_ecp_point * R, const mbedtls_ecp_point * P) Line: 1310
  test.elf! ecp_precompute_comb (const mbedtls_ecp_group * grp, mbedtls_ecp_point * T, const mbedtls_ecp_point * P, unsigned char w, size_t d, mbedtls_ecp_restart_ctx * rs_ctx) Line: 1702
  test.elf! ecp_mul_comb (mbedtls_ecp_group * grp, mbedtls_ecp_point * R, const mbedtls_mpi * m, const mbedtls_ecp_point * P, int (*)(void *, unsigned char *, size_t) f_rng, void * p_rng, mbedtls_ecp_restart_ctx * rs_ctx) Line: 2095
  test.elf! mbedtls_ecp_mul_restartable (mbedtls_ecp_group * grp, mbedtls_ecp_point * R, const mbedtls_mpi * m, const mbedtls_ecp_point * P, int (*)(void *, unsigned char *, size_t) f_rng, void * p_rng, mbedtls_ecp_restart_ctx * rs_ctx) Line: 2396
  test.elf! ecdh_gen_public_restartable (mbedtls_ecp_group * grp, mbedtls_mpi * d, mbedtls_ecp_point * Q, int (*)(void *, unsigned char *, size_t) f_rng, void * p_rng, mbedtls_ecp_restart_ctx * rs_ctx) Line: 84
  test.elf! mbedtls_ecdh_gen_public (mbedtls_ecp_group * grp, mbedtls_mpi * d, mbedtls_ecp_point * Q, int (*)(void *, unsigned char *, size_t) f_rng, void * p_rng) Line: 102
  test.elf! ecdh_make_public_internal (mbedtls_ecdh_context_mbed * ctx, size_t * olen, int point_format, unsigned char * buf, size_t blen, int (*)(void *, unsigned char *, size_t) f_rng, void * p_rng, int restart_enabled) Line: 514
  test.elf! mbedtls_ecdh_make_public (mbedtls_ecdh_context * ctx, size_t * olen, unsigned char * buf, size_t blen, int (*)(void *, unsigned char *, size_t) f_rng, void * p_rng) Line: 542
  test.elf! ssl_write_client_key_exchange (mbedtls_ssl_context * ssl) Line: 3362
  test.elf! mbedtls_ssl_handshake_client_step (mbedtls_ssl_context * ssl) Line: 4015
  test.elf! mbedtls_ssl_handshake_step (mbedtls_ssl_context * ssl) Line: 9564
  test.elf! mbedtls_ssl_handshake (mbedtls_ssl_context * ssl) Line: 9588
  test.elf! https_do_tls_handshake (struct httpsConfigStr * client) Line: 419
  test.elf! HttpsStateMachine Line: 366
  test.elf! HttpsTask (void * param) Line: 110
  test.elf! ?? Line: 110

MBEDTLS VERSION: mbed TLS 2.18.0

PLATFORM: embedded microchip SAME70 micro controller.

I have attached my config.h file.

What am I doing wrong?