Encrypting File System (EFS) in Windows Vista can be used to encrypt the system page file and the per-user Offline Files cache. EFS is also more tightly integrated with enterprise Public Key Infrastructure (PKI), and supports using PKI-based key recovery, data recovery through EFS recovery certificates, or a combination of the two. There are also new Group Policies to require smart cards for EFS, enforce page file encryption, stipulate minimum key lengths for EFS, enforce encryption of the user's Documents folder, and prohibit self-signed certificates. The EFS encryption key cache can be cleared when a user locks his workstation or after a certain time limit.