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)

    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.