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http://www.microsoft.com/technet/prodtechnol/winxppro/deploy/cryptfs.mspxAll exported versions of Windows 2000 use 56-bit key sizes by default unless the 128-bit encryption pack is applied. Workstations that have the 128-bit encryption pack installed may decrypt files with 56-bit key lengths and will encrypt all new files with 128-bit key lengths. However, machines that are only 56-bit-capable may not open files that have been encrypted with 128-bit key lengths. This scenario is especially important where a user has a roaming user profile and may use different machines that have different encryption capabilities.
The Windows XP operating system supports the use of a stronger symmetric algorithm than the default DESX algorithm included with the Windows 2000 operating system. The default algorithm for Windows 2000 and Windows XP is DESX. The default algorithm for Windows XP Service Pack 1 and Windows Server 2003 is Advanced Encryption Standard (AES) using a 256-bit key. For users requiring greater symmetric key strength with a FIPS 140-1 compliant algorithm, the 3DES algorithm can be enabled.
