When you download files from Google Code now (example), in addition to the text version of the SHA1 hash, it includes a QR code of it.
The device that the file was downloaded to is the one that has to hash the file. But, if it can download the file (ie, has access to the webpage), it also has access to the text version of the hash, so the QR code seems completely useless—and more work to decode when the raw text is available. How would reading the hash into a mobile phone allow you to verify the file you download to the computer? Or if you download the file to the phone, how would you use the phone to take a picture of the QR code displayed on the webpage on its own screen?
Does anyone know what the point to the QR code is or how you would use it to verify the downloaded file (I don’t mean QR codes in general, but specifically in this context).
Answer
The QR code contains the file URL not the file SHA1 Checksum. If you check the html for the image you will see the title text says "File download URL". It is common to see these codes in situations where you may need to download the file to a mobile device or access the webpage from a mobile phone..
Programs like QuickMark can be used to scan the QR Code from your phone, and if a site doesn't provide a QR Code you can use something like this Google Chrome QR Code extension to automatically generate one. I use both of these and use them once or twice a month.
You basically then just use the camera on the phone to take a picture of the webpage while it is displayed on your desktop computer and open the URL in the mobile browser, sort of like Copy & Paste between two computers.
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