oath_hotp_generate man page

oath_hotp_generate — API function


#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);


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


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.


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: http://www.gnu.org/software/liboath/ General help using GNU software: http://www.gnu.org/gethelp/


2.6.1 liboath