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14 .Dd May 27, 2023
15 .Dt TOTP 1
16 .Os
17 .Sh NAME
18 .Nm totp
19 .Nd time-based one time password generator
20 .Sh SYNOPSIS
21 .Nm
22 .No < Ns Ar secret
23 .Sh DESCRIPTION
24 .Nm
25 is a time-based one time password generator
26 .Pq TOTP .
27 It reads a secret from standard input and prints the generated password,
28 a numeric code, to standard output.
29 The secret is usually provided by the authenticator
30 .Pq for e.g.\& a website
31 and is either a base32-encoded string or a
32 .Sq otpauth://
33 URI.
34 Blanks in the secret string are ignored, but only one line is read.
35 .Pp
36 .Nm
37 uses a period of 30 seconds, HMAC-SHA1 and generates six digits long
38 codes, unless the URL specifies otherwise.
39 .Sh EXIT STATUS
40 .Ex -std
41 .Sh EXAMPLES
42 .Nm
43 is meant to be used with
44 .Xr plass 1
45 or similar application: the secret is stored safely in the password
46 store and then given to
47 .Nm
48 using a pipe:
49 .Bd -literal -offset indent
50 $ plass cat 2fa/codeberg/op | totp
51 722524
52 .Ed
53 .Sh SEE ALSO
54 .Xr plass 1
55 .Sh STANDARDS
56 .Nm
57 follows the algorithm outlined in RFC 6238
58 .Dq TOTP: Time-Based One-Time Password Algorithm
59 and uses the base32 encoding as defined in RFC 3548
60 .Dq The Base16, Base32, and Base64 Data Encodings .
61 .Sq otpauth://
62 URIs are parsed as per the
63 .Dq Key URI Format
64 proposed by Google Authenticator.
65 .Sh AUTHORS
66 .An -nosplit
67 The
68 .Nm
69 utility was written by
70 .An Omar Polo Aq Mt op@omarpolo.com .