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.