---
name: "Pass::OTP"
section: "3pm"
platform: "linux"
package: "libpass-otp-perl"
version: "1.801-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/Pass::OTP"
---

# Pass::OTP(3pm)

Perl implementation of HOTP / TOTP algorithms

## NAME

Pass::OTP - Perl implementation of HOTP / TOTP algorithms

## SYNOPSIS

```
    use Pass::OTP qw(otp);
    use Pass::OTP::URI qw(parse);
    my $uri = "otpauth://totp/ACME:john.doe@email.com?secret=HXDMVJECJJWSRB3HWIZR4IFUGFTMXBOZ&issuer=ACME&digits=6";
    my $otp_code = otp(parse($uri));
```

## DESCRIPTION

The `"Pass::OTP"` module provides implementation of HOTP and TOTP algorithms according to the RFC 4226 and RFC 6238.

## FUNCTIONS

- hotp(%options)

  Computes HMAC-based One-time Password (RFC 4226).

  ```
      HOTP(K,C) = Truncate(HMAC-SHA-1(K,C))
  ```

  Step 1: Generate an HMAC-SHA-1 value

  ```
      Let HS = HMAC-SHA-1(K,C)
  ```

  Step 2: Generate a 4-byte string (Dynamic Truncation)

  ```
      Let Sbits = DT(HS)
  ```

  Step 3: Compute an HOTP value

  ```
      Let Snum = StToNum(Sbits)       # Convert S to a number in 0..2^{31}-1
      Return D = Snum mod 10^Digit    # D us a number in the range 0..10^{Digit}-1
  ```

- totp(%options)

  Computes Time-based One-time Password (RFC 6238).

  ```
      TOTP = HOTP(K,T)
      T = (Current Unix time - T0) / X
  ```

- otp(%options)

  Convenience wrapper which calls totp/hotp according to options.

## SEE ALSO

Digest::HMAC

[**oathtool**(1)](/oathtool/1.md)

RFC 4226 RFC 6238

\<https://github.com/google/google-authenticator/wiki/Key-Uri-Format\>

## COPYRIGHT AND LICENSE

Copyright (C) 2020 Jan Baier

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.

See \<http://dev.perl.org/licenses/\> for more information.