EVP_DigestUpdate(&ctx,s->s2->challenge,s->s2->challenge_length);
EVP_DigestUpdate(&ctx,s->s2->conn_id,s->s2->conn_id_length);
EVP_DigestFinal_ex(&ctx,km,NULL);
EVP_DigestUpdate(&ctx,s->s2->challenge,s->s2->challenge_length);
EVP_DigestUpdate(&ctx,s->s2->conn_id,s->s2->conn_id_length);
EVP_DigestFinal_ex(&ctx,km,NULL);