BN_CTX_start(3) OpenSSL BN_CTX_start(3) NNAAMMEE BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables SSYYNNOOPPSSIISS #include void BN_CTX_start(BN_CTX *ctx); BIGNUM *BN_CTX_get(BN_CTX *ctx); void BN_CTX_end(BN_CTX *ctx); DDEESSCCRRIIPPTTIIOONN These functions are used to obtain temporary BBIIGGNNUUMM variables from a BBNN__CCTTXX (which can been created by using _B_N___C_T_X___n_e_w(3)) in order to save the overhead of repeatedly creating and freeing BBIIGGNNUUMMs in functions that are called from inside a loop. A function must call _B_N___C_T_X___s_t_a_r_t_(_) first. Then, _B_N___C_T_X___g_e_t_(_) may be called repeatedly to obtain temporary BBIIGGNNUUMMs. All _B_N___C_T_X___g_e_t_(_) calls must be made before calling any other functions that use the ccttxx as an argument. Finally, _B_N___C_T_X___e_n_d_(_) must be called before returning from the func- tion. When _B_N___C_T_X___e_n_d_(_) is called, the BBIIGGNNUUMM pointers obtained from _B_N___C_T_X___g_e_t_(_) become invalid. RREETTUURRNN VVAALLUUEESS _B_N___C_T_X___s_t_a_r_t_(_) and _B_N___C_T_X___e_n_d_(_) return no values. _B_N___C_T_X___g_e_t_(_) returns a pointer to the BBIIGGNNUUMM, or NNUULLLL on error. Once _B_N___C_T_X___g_e_t_(_) has failed, the subsequent calls will return NNUULLLL as well, so it is sufficient to check the return value of the last _B_N___C_T_X___g_e_t_(_) call. In case of an error, an error code is set, which can be obtained by _E_R_R___g_e_t___e_r_r_o_r(3). SSEEEE AALLSSOO _B_N___C_T_X___n_e_w(3) HHIISSTTOORRYY _B_N___C_T_X___s_t_a_r_t_(_), _B_N___C_T_X___g_e_t_(_) and _B_N___C_T_X___e_n_d_(_) were added in OpenSSL 0.9.5. 1.0.2u 2019-12-20 BN_CTX_start(3)