Microsoft Technet is a website for IT Professionals containing download,library,community content,troublshooting and support forum etc. All new downloads are firstly made on this website. Like Windows 7 and Windows Server 2008 R2 are available to download with their keys.
But you need to have Technet plus subscription that could cost 349$ per year.
Microsoft has allowed free users to view the downloads list containg, DVD and ISO images with their hashes. You could see SHA1 hashes and match them against the images you got from some source other than Microsoft.
To view the hashed open
Click Sign in from the Right Top corner,On the right side you can see My Technet Subscription, click on Existing Subscription. On the Technet Benefits Management page, click on the downoads
Here you can see all the products catalogue. But the keys and downloads button will be greyed out because you do not have a subscription. You can see the products with their details only.