# RFC Errata

#### RFC 4226, "HOTP: An HMAC-Based One-Time Password Algorithm", December 2005

Source of RFC: IETF - NON WORKING GROUPArea Assignment: sec

Errata ID: 2405

**Status: Held for Document Update
Type: Technical
Publication Format(s) : TEXT**

Reported By: Alfred Hoenes

Date Reported: 2006-01-18

Held for Document Update by: Sean Turner

Date Held: 2010-07-30

Section A.4.1 says:

(6) [ typos in mathematical text ] Lemma 1 and its proof in Appendis A.4.1, on page 20, contains several typos. In Lemma 1, the line, P_{N,m}(z) = Pr [x mod m = z : x randomly pick in Z_{n}] ^^^ should read: P_{N,m}(z) = Pr [x mod m = z : x randomly pick in Z_{N}] This corrects the use of an undefined variable, n, by using the variable N as expected from the LHS term. In the Proof of Lemma 1, the case distinction for z contains an improper relational operator at two places. To adjust to the possible range of values (cf. item (2) above!), the formula parts: P_{N,m}(z) = [ ... ] = mq/N * 1/m + (N - mq)/N * 1 / (N - mq) if 0 <= z < N - mq | 0 if N - mq <= z <= m ^^^^ = q/N + r/N * 1 / r if 0 <= z < N - mq | 0 if r <= z <= m ^^^^ should be modified to read: P_{N,m}(z) = [ ... ] = mq/N * 1/m + (N - mq)/N * 1 / (N - mq) if 0 <= z < N - mq | 0 if N - mq <= z < m = q/N + r/N * 1 / r if 0 <= z < N - mq | 0 if r <= z < m

It should say:

see above

Notes:

typos