RAND_egd(3) OpenSSL RAND_egd(3) NNAAMMEE RAND_egd, RAND_egd_bytes, RAND_query_egd_bytes - query entropy gather- ing daemon SSYYNNOOPPSSIISS #include int RAND_egd(const char *path); int RAND_egd_bytes(const char *path, int bytes); int RAND_query_egd_bytes(const char *path, unsigned char *buf, int bytes); DDEESSCCRRIIPPTTIIOONN _R_A_N_D___e_g_d_(_) queries the entropy gathering daemon EGD on socket ppaatthh. It queries 255 bytes and uses _R_A_N_D___a_d_d(3) to seed the OpenSSL built-in PRNG. RAND_egd(path) is a wrapper for RAND_egd_bytes(path, 255); _R_A_N_D___e_g_d___b_y_t_e_s_(_) queries the entropy gathering daemon EGD on socket ppaatthh. It queries bbyytteess bytes and uses _R_A_N_D___a_d_d(3) to seed the OpenSSL built-in PRNG. This function is more flexible than _R_A_N_D___e_g_d_(_). When only one secret key must be generated, it is not necessary to request the full amount 255 bytes from the EGD socket. This can be advanta- geous, since the amount of entropy that can be retrieved from EGD over time is limited. _R_A_N_D___q_u_e_r_y___e_g_d___b_y_t_e_s_(_) performs the actual query of the EGD daemon on socket ppaatthh. If bbuuff is given, bbyytteess bytes are queried and written into bbuuff. If bbuuff is NULL, bbyytteess bytes are queried and used to seed the OpenSSL built-in PRNG using _R_A_N_D___a_d_d(3). NNOOTTEESS On systems without /dev/*random devices providing entropy from the ker- nel, the EGD entropy gathering daemon can be used to collect entropy. It provides a socket interface through which entropy can be gathered in chunks up to 255 bytes. Several chunks can be queried during one con- nection. EGD is available from http://www.lothar.com/tech/crypto/ ("perl Make- file.PL; make; make install" to install). It is run as eeggdd _p_a_t_h, where _p_a_t_h is an absolute path designating a socket. When _R_A_N_D___e_g_d_(_) is called with that path as an argument, it tries to read random bytes that EGD has collected. _R_A_N_D___e_g_d_(_) retrieves entropy from the daemon using the daemon's "non-blocking read" command which shall be answered immediately by the daemon without waiting for additional entropy to be collected. The write and read socket operations in the communication are blocking. Alternatively, the EGD-interface compatible daemon PRNGD can be used. It is available from http://prngd.sourceforge.net/ . PRNGD does employ an internal PRNG itself and can therefore never run out of entropy. OpenSSL automatically queries EGD when entropy is requested via _R_A_N_D___b_y_t_e_s_(_) or the status is checked via _R_A_N_D___s_t_a_t_u_s_(_) for the first time, if the socket is located at /var/run/egd-pool, /dev/egd-pool or /etc/egd-pool. RREETTUURRNN VVAALLUUEE _R_A_N_D___e_g_d_(_) and _R_A_N_D___e_g_d___b_y_t_e_s_(_) return the number of bytes read from the daemon on success, and -1 if the connection failed or the daemon did not return enough data to fully seed the PRNG. _R_A_N_D___q_u_e_r_y___e_g_d___b_y_t_e_s_(_) returns the number of bytes read from the daemon on success, and -1 if the connection failed. The PRNG state is not con- sidered. SSEEEE AALLSSOO _r_a_n_d(3), _R_A_N_D___a_d_d(3), _R_A_N_D___c_l_e_a_n_u_p(3) HHIISSTTOORRYY _R_A_N_D___e_g_d_(_) is available since OpenSSL 0.9.5. _R_A_N_D___e_g_d___b_y_t_e_s_(_) is available since OpenSSL 0.9.6. _R_A_N_D___q_u_e_r_y___e_g_d___b_y_t_e_s_(_) is available since OpenSSL 0.9.7. The automatic query of /var/run/egd-pool et al was added in OpenSSL 0.9.7. 1.0.2u 2019-12-20 RAND_egd(3)