oath_hotp_generate(3)

NAME
oath_hotp_generate - API function

SYNOPSIS
#include <oath.h>

int oath_hotp_generate(const char * secret, size_t secret_length, uint64_t moving_factor, unsigned digits, bool add_checksum, size_t truncation_offset, char * output_otp);

ARGUMENTS

const char * secret
    the shared secret string

size_t secret_length
    length of secret

uint64_t moving_factor
    a counter indicating the current OTP to generate

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

bool add_checksum
    whether to add a checksum digit or not

size_t truncation_offset
    use a specific truncation offset

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

DESCRIPTION
Generate a one-time-password using the HOTP algorithm as described in RFC 4226. Use a value of OATH_HOTP_DYNAMIC_TRUNCATION for truncation_offset unless you really need a specific truncation offset. To find out the size of the OTP you may use the OATH_HOTP_LENGTH() macro. The output_otp buffer must be have room for that length plus one for the terminating NUL. Currently only values 6, 7 and 8 for digits are supported, and the add_checksum value is ignored. These restrictions may be lifted in future versions, although some limitations are inherent in the protocol.

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

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

COPYRIGHT
Copyright © 2009-2025 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.