July 12, 2012, 11:51 AM — Starting next month, updated Windows operating systems will reject encryption keys smaller than 1024 bits, which
could cause problems for customer applications accessing Web sites and email platforms that use the keys.
The cryptographic policy change is part of Microsoft's response to security weaknesses that came to light after
Windows Update became an unwitting party to Flame Malware attacks, and affects Windows XP, Windows Server 2003, Windows Server 2003 R2, Windows Vista, Windows
Server 2008, Windows 7, and Windows Server 2008 R2 operating systems, according to the Windows PKI blog
written by Kurt L. Hudson, a senior technical writer for the company.
"To prepare for this update, you should determine whether your organization is currently using keys less than
1024 bits," Hudson writes. "If it is, then you should take steps to update your cryptographic settings such that
keys under 1024 bits are not in use."
Even with preparation, updated machines may face issues such as error messages when browsing to Web sites with
SSL certificates that are below the minimum 1024. They may also face problems enrolling for certificates when
certificate requests use a 1024 or less key, the blog says. Installing Active X controls signed with 1024-bit or
less signatures will also fail.
The same is true for installing applications signed with less-than 1024-bit signatures. The exception is those
applications signed before Jan. 1, 2010, which will be allowed by default, the blog says.
The use of cryptographic keys shorter than 1024 bits makes them too vulnerable to brute-force attacks, Microsoft
says, something that is widely recognized and dealt with, but not universally.
The biggest challenge for businesses getting ready for the change will likely be with legacy, in-house
applications that interact with Windows platforms, says John Pironti, president of IP Architects and the security
track leader for Interop.