One-Time Pad Algorithms

Functions
void	lc_hotp (const uint8_t *hmac_key, size_t hmac_key_len, uint64_t counter, uint32_t digits, uint32_t *hotp_val)
	HMAC-Based One-Time Password Algorithm - RFC 4226.
int	lc_totp (const uint8_t *hmac_key, size_t hmac_key_len, uint32_t step, uint32_t digits, uint32_t *totp_val)
	Time-Based One-Time Password Algorithm - RFC 6238.

Detailed Description

Function Documentation

lc_hotp()

void lc_hotp	(	const uint8_t *	hmac_key,
		size_t	hmac_key_len,
		uint64_t	counter,
		uint32_t	digits,
		uint32_t *	hotp_val )

HMAC-Based One-Time Password Algorithm - RFC 4226.

The HOTP algorithm uses HMAC SHA-256

Parameters

[in]	hmac_key	Seed key / HMAC key K - shared secret between client and server; each HOTP generator has a different and unique secret K.
[in]	hmac_key_len	Seed key / HMAC key length
[in]	counter	Counter C - 8-byte counter value, the moving factor. This counter MUST be synchronized between the HOTP generator (client) and the HOTP validator (server).
[in]	digits	number of digits in an HOTP value; system parameter.
[out]	hotp_val	HOTP output value

lc_totp()

int lc_totp	(	const uint8_t *	hmac_key,
		size_t	hmac_key_len,
		uint32_t	step,
		uint32_t	digits,
		uint32_t *	totp_val )

Time-Based One-Time Password Algorithm - RFC 6238.

The TOTP algorithm uses HMAC SHA-256

Parameters

[in]	hmac_key	Seed key / HMAC key K - shared secret between client and server; each HOTP generator has a different and unique secret K.
[in]	hmac_key_len	Seed key / HMAC key length
[in]	step	Time step in seconds - to use the default value of 30 seconds, use 30
[in]	digits	number of digits in a TOTP value; system parameter.
[out]	totp_val	TOTP output value