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*[endroid/qr-code](https://github.com/endroid/qr-code) if using `EndroidQrCodeProvider`.
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*[endroid/qr-code](https://github.com/endroid/qr-code) if using `EndroidQrCodeProvider` or `EndroidQrCodeWithLogoProvider`.
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*[bacon/bacon-qr-code](https://github.com/Bacon/BaconQrCode) if using `BaconQrCodeProvider`.
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## Installation
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2.`ImageChartsQRCodeProvider`
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3.`QRicketProvider`
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4.`EndroidQrCodeProvider` (requires `endroid/qr-code` to be installed)
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5.`BaconQrCodeProvider` (requires `bacon/bacon-qr-code` to be installed)
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5.`EndroidQrCodeWithLogoProvider` (same, but supporting embedded images)
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6.`BaconQrCodeProvider` (requires `bacon/bacon-qr-code` to be installed)
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...or implement your own provider. To implement your own provider all you need to do is implement the `IQRCodeProvider` interface. You can use the built-in providers mentioned before to serve as an example or read the next chapter in this file. The built-in classes all use a 3rd (e.g. external) party (Image-charts, QRServer and QRicket) for the hard work of generating QR-codes (note: each of these services might at some point not be available or impose limitations to the number of codes generated per day, hour etc.). You could, however, easily use a project like [PHP QR Code](http://phpqrcode.sourceforge.net/) (or one of the [many others](https://packagist.org/search/?q=qr)) to generate your QR-codes without depending on external sources. Later on we'll [demonstrate](#qr-code-providers) how to do this.
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@@ -96,7 +97,9 @@ When the shared secret is added to the app, the app will be ready to start gener
`verifyCode()` will return either `true` (the code was valid) or `false` (the code was invalid; no points for you!). You may need to store `$secret` in a `$_SESSION` or other persistent storage between requests. The `verifyCode()` accepts, aside from `$secret` and `$code`, three more arguments. The first being `$discrepancy`. Since TOTP codes are based on time("slices") it is very important that the server (but also client) have a correct date/time. But because the two *may* differ a bit we usually allow a certain amount of leeway. Because generated codes are valid for a specific period (remember the `$period` argument in the `TwoFactorAuth`'s constructor?) we usually check the period directly before and the period directly after the current time when validating codes. So when the current time is `14:34:21`, which results in a 'current timeslice' of `14:34:00` to `14:34:30` we also calculate/verify the codes for `14:33:30` to `14:34:00` and for `14:34:30` to `14:35:00`. This gives us a 'window' of `14:33:30` to `14:35:00`. The `$discrepancy` argument specifies how many periods (or: timeslices) we check in either direction of the current time. The default `$discrepancy` of `1` results in (max.) 3 period checks: -1, current and +1 period. A `$discrepancy` of `4` would result in a larger window (or: bigger time difference between client and server) of -4, -3, -2, -1, current, +1, +2, +3 and +4 periods.
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If you do extra validations with your `$_POST` values, just make sure the code is still submitted as string - even if that's a numeric code, casting it to integer is unreliable. Also, you may need to store `$secret` in a `$_SESSION` or other persistent storage between requests. `verifyCode()` will return either `true` (the code was valid) or `false` (the code was invalid; no points for you!).
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The `verifyCode()` accepts, aside from `$secret` and `$code`, three more arguments, with the first being `$discrepancy`. Since TOTP codes are based on time("slices") it is very important that the server (but also client) have a correct date/time. But because the two *may* differ a bit we usually allow a certain amount of leeway. Because generated codes are valid for a specific period (remember the `$period` argument in the `TwoFactorAuth`'s constructor?) we usually check the period directly before and the period directly after the current time when validating codes. So when the current time is `14:34:21`, which results in a 'current timeslice' of `14:34:00` to `14:34:30` we also calculate/verify the codes for `14:33:30` to `14:34:00` and for `14:34:30` to `14:35:00`. This gives us a 'window' of `14:33:30` to `14:35:00`. The `$discrepancy` argument specifies how many periods (or: timeslices) we check in either direction of the current time. The default `$discrepancy` of `1` results in (max.) 3 period checks: -1, current and +1 period. A `$discrepancy` of `4` would result in a larger window (or: bigger time difference between client and server) of -4, -3, -2, -1, current, +1, +2, +3 and +4 periods.
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The second, `$time`, allows you to check a code for a specific point in time. This argument has no real practical use but can be handy for unittesting etc. The default value, `null`, means: use the current time.
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@@ -128,7 +131,7 @@ public function verifyCode($secret, $code, $discrepancy = 1, $time = null): bool
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As mentioned before, this library comes with five 'built-in' QR-code providers. This chapter will touch the subject a bit but most of it should be self-explanatory. The `TwoFactorAuth`-class accepts a `$qrcodeprovider` argument which lets you specify a built-in or custom QR-code provider. All five built-in providers do a simple HTTP request to retrieve an image using cURL and implement the [`IQRCodeProvider`](lib/Providers/Qr/IQRCodeProvider.php) interface which is all you need to implement to write your own QR-code provider.
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The default provider is the [`QRServerProvider`](lib/Providers/Qr/QRServerProvider.php) which uses the [goqr.me API](http://goqr.me/api/doc/create-qr-code/) to render QR-codes. Then we have the [`ImageChartsQRCodeProvider`](lib/Providers/Qr/ImageChartsQRCodeProvider.php) which uses the [image-charts.com replacement for Google Image Charts](https://image-charts.com) to render QR-codes and the [`QRicketProvider`](lib/Providers/Qr/QRicketProvider.php) which uses the [QRickit API](http://qrickit.com/qrickit_apps/qrickit_api.php). These three providers all inherit from a common (abstract) baseclass named [`BaseHTTPQRCodeProvider`](lib/Providers/Qr/BaseHTTPQRCodeProvider.php) because all three share the same functionality: retrieve an image from a 3rd party over HTTP. Finally, we have [`EndroidQrCodeProvider`](lib/Providers/Qr/EndroidQrCodeProvider.php) and [`BaconQrCodeProvider`](lib/Providers/Qr/BaconQrCodeProvider.php) which require an optional dependency to be installed to use (see Requirements section above), but will generate the QR codes locally. All five classes have constructors that allow you to tweak some settings and most, if not all, arguments should speak for themselves. If you're not sure which values are supported, click the links in this paragraph for documentation on the API's that are utilized by these classes.
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The default provider is the [`QRServerProvider`](lib/Providers/Qr/QRServerProvider.php) which uses the [goqr.me API](http://goqr.me/api/doc/create-qr-code/) to render QR-codes. Then we have the [`ImageChartsQRCodeProvider`](lib/Providers/Qr/ImageChartsQRCodeProvider.php) which uses the [image-charts.com replacement for Google Image Charts](https://image-charts.com) to render QR-codes and the [`QRicketProvider`](lib/Providers/Qr/QRicketProvider.php) which uses the [QRickit API](http://qrickit.com/qrickit_apps/qrickit_api.php). These three providers all inherit from a common (abstract) baseclass named [`BaseHTTPQRCodeProvider`](lib/Providers/Qr/BaseHTTPQRCodeProvider.php) because all three share the same functionality: retrieve an image from a 3rd party over HTTP. Finally, we have [`EndroidQrCodeProvider`](lib/Providers/Qr/EndroidQrCodeProvider.php), [`EndroidQrCodeWithLogoProvider`](lib/Providers/Qr/EndroidQrCodeWithLogoProvider.php) and [`BaconQrCodeProvider`](lib/Providers/Qr/BaconQrCodeProvider.php) which require an optional dependency to be installed to use (see Requirements section above), but will generate the QR codes locally. All five classes have constructors that allow you to tweak some settings and most, if not all, arguments should speak for themselves. If you're not sure which values are supported, click the links in this paragraph for documentation on the API's that are utilized by these classes.
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If you don't like any of the built-in classes because you don't want to rely on external resources for example or because you're paranoid about sending the TOTP secret to these 3rd parties (which is useless to them since they miss *at least one* other factor in the [MFA process](http://en.wikipedia.org/wiki/Multi-factor_authentication)), feel tree to implement your own. The `IQRCodeProvider` interface couldn't be any simpler. All you need to do is implement 2 methods:
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