StrongAuth (Two-Factor Authentication) iOS client.
Author: Dave MacLachlan <dmaclach@google.com


This client generates and displays one time passwords for logging in to
GAIA, or any other system which supports HOTP[1] or TOTP[2].

It is designed to be configured via a URL handler, as follows:

  otpauth://TYPE/LABEL?PARAMETERS

where TYPE is "hotp" or "totp" and LABEL is a human readable label to help
distinguish multiple otp generators.

The supported PARAMETERS are:

  algorithm=(SHA1|SHA256|SHA512|MD5)
    OPTIONAL, defaults to SHA1.

  secret=[websafe Base64 encoded secret key, no padding]
    REQUIRED, 128 bits or more.

  digits=(6|8)
    OPTIONAL, defaults to 6.

  counter=N  (hotp specific)
    REQUIRED

  period=N  (totp specific)
    OPTIONAL, defaults to 30.

References:
1. HOTP: An HMAC-Based One-Time Password Algorithm
   http://tools.ietf.org/html/rfc4226
2. TOTP: Time-based One-time Password Algorithm
   http://tools.ietf.org/html/draft-mraihi-totp-timebased
