NAME

       oath_totp_generate - API function

SYNOPSIS

       #include <oath.h>

       int  oath_totp_generate(const  char  * secret, size_t secret_length, time_t now, unsigned time_step_size,
       time_t start_offset, unsigned digits, char * output_otp);

ARGUMENTS

       const char * secret
                   the shared secret string

       size_t secret_length
                   length of secret

       time_t now  Unix time value to compute TOTP for

       unsigned time_step_size
                   time step system parameter (typically 30)

       time_t start_offset
                   Unix time of when to start counting time steps (typically 0)

       unsigned digits
                   number of requested digits in the OTP, excluding checksum

       char * output_otp
                   output buffer, must have room for the output OTP plus zero

DESCRIPTION

       Generate a one-time-password using the time-variant TOTP algorithm described  in  RFC  6238.   The  input
       parameters are taken as time values.

       The  system parameter time_step_size describes how long the time window for each OTP is.  The recommended
       value is 30 seconds, and you can use the  value  0  or  the  symbol  OATH_TOTP_DEFAULT_TIME_STEP_SIZE  to
       indicate this.

       The  system  parameter  start_offset denote the Unix time when time steps are started to be counted.  The
       recommended  value  is  0,  to  fall  back  on  the  Unix   epoch)   and   you   can   use   the   symbol
       OATH_TOTP_DEFAULT_START_TIME to indicate this.

       The output_otp buffer must have room for at least digits characters, plus one for the terminating NUL.

       Currently  only  values  6,  7  and 8 for digits are supported.  This restriction may be lifted in future
       versions.

RETURNS

       On success, OATH_OK (zero) is returned, otherwise an error code is returned.

SINCE

       1.4.0

REPORTING BUGS

       Report bugs to <oath-toolkit-help@nongnu.org>.  liboath home  page:  https://www.nongnu.org/oath-toolkit/
       General help using GNU software: http://www.gnu.org/gethelp/

COPYRIGHT

       Copyright © 2009-2020 Simon Josefsson.
       Copying  and distribution of this file, with or without modification, are permitted in any medium without
       royalty provided the copyright notice and this notice are preserved.

liboath                                              2.6.11                                oath_totp_generate(3)