protocol

otp_protocol

Protocol for HOTP and TOTP generation and verification as specified in RFC 4226 and RFC 6238.

Availability:

logtalk_load(otp(loader))

Author: Paulo Moura

Version: 1:0:0

Date: 2026-07-14

Compilation flags:

static

Dependencies:

(none)

Remarks:

(none)

Inherited public predicates:

(none)

Public predicates

hotp/5

Computes an HOTP value for the given hash object, secret, moving counter, and number of digits. The secret can be either a raw byte list or a Base32 wrapper term of the form base32(atom(Atom)), base32(chars(Chars)), or base32(codes(Codes)).

Compilation flags:

static

Template:

hotp(Hash,Secret,Counter,Digits,OTP)

Mode and number of proofs:

hotp(+object_identifier,+term,+integer,+integer,--atom) - one

---

totp/5

Computes a TOTP value using the standard 30-second time step and Unix epoch T0 = 0 for the given hash object, secret, Unix time, and number of digits.

Compilation flags:

static

Template:

totp(Hash,Secret,UnixTime,Digits,OTP)

Mode and number of proofs:

totp(+object_identifier,+term,+integer,+integer,--atom) - one

---

hotp_verify/7

Verifies an HOTP value by searching from the given counter through the bounded forward counter window. Returns the matched counter on success.

Compilation flags:

static

Template:

hotp_verify(Hash,Secret,Counter,Window,Digits,OTP,MatchedCounter)

Mode and number of proofs:

hotp_verify(+object_identifier,+term,+integer,+integer,+integer,+atom,--integer) - zero_or_one_or_error

---

totp_verify/7

Verifies a TOTP value by searching within the bounded symmetric time-step window around the current time step. Returns the matched time step on success.

Compilation flags:

static

Template:

totp_verify(Hash,Secret,UnixTime,Window,Digits,OTP,MatchedTimeStep)

Mode and number of proofs:

totp_verify(+object_identifier,+term,+integer,+integer,+integer,+atom,--integer) - zero_or_one_or_error

---

Protected predicates

(none)

Private predicates

(none)

Operators

(none)

See also

hmac_protocol