Abstract:
User accounts, authentication information and user home directories are stored on an external storage media that can be transferred from one device to another. Measures are included for detecting tampering of stored information and for preventing possibly conflicting or damaging account and file information from entering a host device.

Description:
TECHNICAL FIELD 
     The subject matter of this application is generally related to computer account management. 
     BACKGROUND 
     User account data typically includes a user name, an account identifier, a home directory location and management information. For local accounts (i.e., non-network accounts) this information can be stored on a local directory database on a host device. For network accounts, account information can be stored on a network directory server (e.g. LDAP). 
     User authentication information (e.g., a password) can be stored separately. For local accounts, a secure hash of a password can be located in a secure area of a boot hard drive. For network accounts, passwords can be located on an authentication server (e.g., Kerberos™). 
     User home directories are typically the main area where a user keeps their files. For local accounts, the home directory can be located on a local hard disk. For network accounts, the home directory can be located on a network file server. It is often desirable to synchronize versions of home directory folders locally and on the network so that when a user goes offline they can continue to work just as if they were connected to the network. 
     Some known operating systems provide a portable home directory system. For example, Portable Home Directories (PHDs) is the name of a system in Apple Computer Inc.&#39;s Mac® OS X, where a network account, user authentication information and a network home directory can be cached locally on a host device and synchronized with their originals on network servers. The user home directory can be encrypted using a known encryption technology (e.g., FileVault™) and decrypted using, for example, the user&#39;s login password. 
     While conventional portable home directory systems are useful they do not allow a user to transport on an external storage media a complete home directory and account between networked computers without performance degradation (e.g., synchronization delay). 
     SUMMARY 
     User accounts, authentication information and user home directories are stored on an external storage media that can be transferred from one device to another. Measures are included for detecting tampering of stored information and for preventing possibly conflicting or damaging account and file information from entering a host device. 
     In some implementations, a method comprises: providing a login screen for presentation on a display screen of a host device, the login screen including a list of accounts available for log in, where at least one account is associated with an external storage media operatively coupled to the host device; receiving a first input from a user of the host device, the input specifying for log in the local account associated with the external storage media; responsive to the first input, determining if the local account has a corresponding network account; if the local account has a corresponding network account, using the network account and associated authentication methods to authenticate the user of the host device; and if the local account does not have a corresponding network account, using information locally accessible by the host device to authenticate the user. 
     Other implementations of portable computer accounts are disclosed, including implementations directed to systems, methods, apparatuses, computer-readable mediums and user interfaces. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram of an exemplary portable computer account system. 
         FIG. 2A  is a screenshot of an exemplary account login window. 
         FIG. 2B  is a screenshot of an exemplary accounts system preference pane. 
         FIG. 3  is a flow diagram of an exemplary portable computer account creation process. 
         FIGS. 4A-4C  are flow diagrams of an exemplary portable computer account login process. 
         FIG. 5  is a an exemplary host device architecture. 
     
    
    
     DETAILED DESCRIPTION 
     Portable Computer Account System 
       FIG. 1  is a block diagram of an exemplary portable computer account system  100 . The portable computer account system  100  allows the owner of a network account to retrieve a full copy of account information and data contents from a network server and to store the information on an external storage drive attached to a host device which is connected to the network. The account copy, herein referred to as a portable computer account, can be accessed and modified as though the user were logged into the network account. The portable computer account can later be synchronized with the network-resident account data. Data synchronization may be provided with any file synchronization tool or service, for example, iDisk™ or Apple Portable Home Directory™ by Apple Computer of Cupertino, Calif. An example of a framework for implementing synchronization in an application is Apple&#39;s “Sync Services” which is publicly available on Apple&#39;s developer website (http://developer.apple.com). Once the portable computer account is created within the external storage media, it may be accessed locally on a host machine without the need for network connectivity. The portable computer account can be encrypted and/or password protected to keep its contents secure. Any known encryption technique may be used (e.g., RSA, PGP, DES, AES). The portable computer account may be tamper-resistant such that a user can not modify network account information and upload it during network account synchronization. 
     A computer network  110  includes a network server  102  and a network storage device  104 . Any number of user accounts exist on the computer network  110 . User account information for users A, B, and C is stored on the network storage device  104 . The user account information may include user profile information, security information, a home directory path and its contents, etc. A first host device  106  is connected to the network  110 . User A connects to the first host device  106  to access account A stored on network storage device  104 . User A downloads a copy of the account A information and creates a portable computer account on a first external storage media  112  connected to the first host device  106 . The first external storage media  112  may be any type storage media with adequate storage space connected to the first host device  106  via any type connection, e.g. FireWire®, USB, etc. The information contained within the portable computer account A may include, but is not limited to, user preferences, security settings, and home directory contents. The portable computer account A can be encrypted as well as password protected. A hash of user A&#39;s security password is also stored within the external storage media  112 . The password hash allows the host device  106  to protect the portable computer account A by providing a secure login method in the event that the network  110  is not accessible to the host device  106  when user A wishes to access the portable computer account A. Examples of authentication techniques for portable computer accounts is described in U.S. patent application Ser. No. 10/867,299, for “A Method and Apparatus for Authenticating User Access,” filed Jun. 14, 2004, which patent application is incorporated by reference herein in its entirety. 
     Similarly, user B and user C connect to the network  110  via a second host device  108  to create portable computer accounts of account B and account C. The account B and account C portable computer accounts and the password hashes for accounts B and C are stored within a second external storage media  114  connected to the second host device  108 . The portable computer accounts can be accessible to the users when network  110  is not available. Once the connection with network  110  has been re-established, any changes made to the data within the portable computer accounts can be synchronized with the network data residing within the network storage media  104 . Any method of synchronization may be used. In one implementation, the account information within the portable computer accounts may be tamper-guarded such that modified account information, such as user privileges or security data, will not be synchronized with the network data. 
       FIG. 2A  is a screenshot of an exemplary account login window  200  for a multi-user host device. The multi-user device may be a personal computer, network terminal device, laptop computer, or any other device capable of allowing multiple users access to a computer network such as network  110  ( FIG. 1 ). A user may select between two accounts available within the login window  200 . Selection of a user account provides the user with login ability for that account. 
     A cursor is placed above the account name of the second user account available within the login window  200 . The mouse-over of the account name causes a dialog box  202  to appear. Within the dialog box  202 , a message, “external drive”, alerts the user that the second user account exists within an external storage media. In one implementation, this may signify that the external storage media containing the second user account is presently connected to the host device displaying the login window  200 , and that a portable computer account exists within the external storage media. In one implementation, a modified account icon or additional account name description may alert the user that the account is a portable computer account accessible from an external storage media. 
       FIG. 2B  is a screenshot of an exemplary accounts system preference pane  204 . The preference pane  204  provides a user with options regarding that user&#39;s account information. For example, a user may be capable of accessing and/or modifying password settings, account privileges, system preferences, etc. through the preference pane  204 . In one implementation, the preference pane  204  may be accessed through a desktop menu. 
     A user is logged into an existing network account  206  through a host device connected to a network. The preference pane  204  provides the user with the option to create a portable computer account using a checkbox  208 . In one implementation, a portable computer account may be created on an external storage media. A configure button associated with the checkbox  208  may provide further control over portable computer account details. For example, the configure button may provide the user with external storage media selection, account encryption options, etc. 
     Portable Computer Account Creation Process 
       FIG. 3  is a flow diagram  300  of an exemplary portable computer account creation process. A user may wish to create a portable computer account to obtain a local copy of information contained within a network account. The user may also wish to enable offline access to personal data stored within the network account. A network account may include, but is not limited to, an account name, password, user information, and home directory data. A user logs into a network account through a host device. The user attaches an external storage media to the host device and instructs the creation engine running on the host device to create a portable computer account of the user&#39;s network account on the external storage media (step  302 ). In one implementation, the user may create the portable computer account using the accounts system preference pane  204  as described in  FIG. 2B . The creation engine running on the host device creates a home directory within the external storage media and downloads an initial copy of the network home data to the home directory. 
     During portable computer account creation, the creation engine may optionally encrypt the data (step  304 ). Any encryption method may be used. The encrypted data could be protected with the user&#39;s network password or with another means of secure access. 
     Next, the creation engine makes a near-copy of the user&#39;s account information and stores it in a database file (step  306 ). The account information is a near-copy rather than a copy because it is modified to function properly within the environment of the external storage media and the host device system. For example, the home directory path may be updated to reflect the path to the home directory within the external storage media. The near-copy may be stored within the user&#39;s new home directory on the external storage media. In another implementation, the near-copy is stored separately from the home directory, for example within the same parent folder, such that it can be read without decrypting the home directory. 
     The creation engine now generates and stores a secure one-way hash of the user&#39;s network login password on the external storage media (step  308 ). The creation engine stores the password hash separately from any data which has been encrypted using that password. The password hash allows the user to log into the account securely without requiring access to the network. In one implementation, another authentication technique can be used, for example, one utilizing the encryption engine in MAC OS® X FileVault™ by Apple Computer, Inc. of Cupertino, Calif., U.S.A. 
     Portable Computer Account Login Process 
       FIG. 4A  is a flow diagram of an exemplary portable computer account login process  400 . The portable computer account software running on the host device locates and lists portable computer accounts for user access. The host device may be, but is not limited to, a personal computer, network access terminal, laptop computer, mobile phone, personal digital assistant (PDA), media player, etc. The portable computer account login process  400  may begin, for example, at system start-up or when a current user logs out of the host device. Alternatively, the process  400  may be user or event triggered, for example when the host device recognizes the addition of external storage media. 
     The portable computer account login process  400  begins by scanning the host device for external storage media (step  402 ). There may be any number of external storage media attached to the host device. The external storage media may be connected to the host device in any suitable manner, i.e., Firewire®, USB, wireless, etc. The process  400  continues to scan until external storage media is found (step  404 ). 
     Once external storage media is located, the process  400  mounts the external storage media and searches it for account database files associated with a portable computer account (step  406 ). Any number of account database files may be stored within an external storage media. If no account database files are located within the external storage media, the process  400  unmounts the external storage media (step  409 ) and continues to scan for further external storage media (step  402 ). 
     Once an external storage media containing account database files has been found (step  408 ), the process  400  examines the account information within the account database file to determine whether or not the account should be shown within the login window (step  410 ). In one implementation, the login window may be the login window  200  as described in  FIG. 2A . In one implementation, the process  400  may not allow the account to be added to the login window if another account of the same name or identifier already exists within the local directory database of user accounts. In one implementation, the account may not be added to the local directory database because the process  400  has, for some reason, deemed it detrimental to the security of the host device. 
       FIG. 4B  is a continuation of the flow diagram  400  of an exemplary portable computer account login process  400 . The process  400  considers whether or not the portable computer account it has located is safe for the host device (step  412 ). In one implementation, an account is deemed unsafe if it poses any threat to the security of the host device. For example, an unsafe account may be one which has administrative privileges. If the process  400  determines that the account is safe (step  412 ), the process  400  adds the account to the local directory database, displays the account within the login window, and adds a hash of the account&#39;s password to the host device (step  414 ). In one implementation, the account is displayed within the login window  200 , as described in  FIG. 2A . 
     If, instead, the process  400  decides that the account is not safe (step  412 ), the process  400  adds a safe version of the account to the local directory database, displays the account information within the login window, and marks the account with the reason as to why it is considered unsafe (step  416 ). In one implementation, to create a safe version of an account, the process  400  may remove any access rights and privileges that could provide the user with the opportunity to corrupt the host device. For example, the process  400  may remove administrative privileges from the account before allowing it to be added. 
     In marking the account with the reason why it was deemed unsafe, in one implementation, the process  400  associates an icon with the account which signifies the purpose of the account modification. In another implementation, a mouse-over of the account listing can provide details regarding its unsafe status, for example within a dialog box (e.g., dialog box  202 ). Any other method of marking an unsafe account may instead be used. 
     Rather than adding the safe version of the account to the local directory database, in one implementation, the process  400  adds the safe version to a temporary directory listing, pending user validation (e.g. password acceptance). In one implementation, the process  400  does not add the account to the database due to restrictions such as duplicate account identification. In this circumstance, the process  400  may notify the user as to reason of the failure of account addition, and then the process  400  may return to scanning for external storage media (step  402 ). 
     Once the account has been added to the local directory database, the process  400  next receives user input specifying an account selection (step  418 ). In one implementation, the user selects from accounts displayed within a login window such as the login window  200 , described in  FIG. 2A . The process  400  compares the account information stored within the external storage media to accounts available on the network to determine if a matching network account exists (step  420 ). In one implementation, the process  400  compares one or more account identifiers (e.g. user name, “short name”, globally unique identifier (GUID), etc) to information available within directory servers bound to the host device. 
     In  FIG. 4C , the flow diagram of an exemplary portable computer account login process  400  continues. If the process  400  does not locate a matching network account (step  422 ), the process  400  uses the network account password hash for the user verification login process (step  424 ). This option allows the user to login to the portable computer account via the host device when the network is disconnected or otherwise unavailable. In one implementation, the process  400  may use a verification method other than a password hash to establish user validity. If the verification is unsuccessful (step  428 ), the process  400  denies the user login and returns to scanning for external storage media (step  402 ). The user may be given any number of attempts at password validation before login refusal occurs. 
     If the verification is successful (step  428 ), the process prompts the user for the name and password of an administrator account within the host device (step  432 ). This can verify that the user has local directory access rights within this machine. It can also provide a means of guarding against users who wish to corrupt the host device. If the user is unable to provide a correct name and password for an administrator account within the host device (step  434 ), the user is denied login. The user may be allowed any number of attempts before login refusal occurs. The process  400  then returns to scanning for external storage media (step  402 ). 
     If the administrator account verification is instead successful (step  434 ), the process  400  adds the portable computer account to the approved account list (step  436 ). In one implementation, account approval signifies that the step of providing administrator login verification may not be required the next time the user logs into this account through this host device. In one implementation, the user may have the option, for example via a checkbox within the login dialog, as to whether or not the account should be added to the approved list. For example, the computer administrator may wish to only temporarily allow portable computer account login so that he can be personally involved when a portable computer account is used on his computer or device. The login is allowed to proceed (step  438 ). In one implementation, the process  400  decrypts the home directory data within the external storage media and the user now has access to the portable computer account. 
     In the circumstance that the user&#39;s matching network account had been found (step  422 ), the process  400  uses the network account and its associated authentication methods to authenticate the user (step  426 ). In this manner, the user&#39;s network account, even when copied to a host device to be accessed locally, may benefit from the security measures provided by the network account access method. Additionally, by logging in via the network rather than using the locally-stored password hash, the host device has immediate access to the network-resident account information to perform data synchronization if desired. 
     The process  400  overwrites the user&#39;s network account information in the local directory database and the account database file stored on the external storage media with the network account information (step  430 ). This allows for immediate synchronization of the locally-stored account information. In one implementation, the locally-stored account information is selectively updated, such that, for example, the home directory path isn&#39;t overwritten to point to a directory path which does not exist within the external storage media. 
     The process  400  adds the portable computer account to the approved account list (step  436 ). In one implementation, addition to the approved account list may mean that, in the event of the network being unavailable during the next login attempt, matching the password of the locally-stored hash will be adequate to gain access to the portable computer account. In one implementation, the user may have the option, for example via a checkbox within the login dialog, as to whether or not the account should be added to the approved list. For example, the user may wish to leave the extra level of security within the login process to protect the portable computer account. 
     The login is allowed to proceed (step  438 ). In one implementation, the process decrypts the home directory data within the external storage media and the user now has access to the portable computer account. The process  400  may additionally synchronize the home directory within the external storage media with the network home directory data. In one implementation, user authorization is required for home directory data synchronization to occur. In one implementation, any other accounts found within the external storage media which are not on the approved list may now be removed from the host device account listing. 
     Host Device Architecture 
       FIG. 5  is a block diagram of an exemplary host device architecture  500  for hosting the process  400 , described in reference to  FIGS. 4A-4C . Other architectures are possible, including architectures with more or fewer components. 
     In some implementations, the host device architecture  500  includes one or more processors  502  (e.g., dual-core Intel® Xeon® Processors), a display device  504  (e.g., an LCD), a local directory database  506 , a network interface  508  (e.g., a Ethernet, USB, Firewire®), one or more input devices  510  (e.g., mouse, keyboard) and one or more computer-readable mediums  512  (e.g., RAM, ROM, SDRAM, hard disk, optical disk, flash memory, SAN, etc.). The network interface  508  is operatively coupled to an external storage media  509 . 
     The components of the host device architecture  500  described above can exchange communications and data over one or more buses  514  (e.g., EISA/ISA, PCI, PCI-Express) for facilitating the transfer of data and control signals between the component of the architecture  500 . 
     The term “computer-readable medium” refers to any medium that participates in providing instructions to a processor  502  for execution, including without limitation, non-volatile media (e.g., optical or magnetic disks), volatile media (e.g., memory) and transmission media. Transmission media includes, without limitation, coaxial cables, copper wire and fiber optics. Transmission media can also take the form of acoustic, light or radio frequency waves. 
     The computer-readable medium  512  further includes an operating system  516  (e.g., Mac OS®, Windows® XP, Linux® OS), a network communication module  518 , a browser  520 , and login window system  522  and a portable computer account module  524 . The operating system  516  can be multi-user, multiprocessing, multitasking, multithreading, real time, etc. The operating system  516  performs basic tasks, including but not limited to: recognizing input from the input devices  508  and providing output to the display device  504 ; keeping track and managing files and directories on computer-readable mediums  512  (e.g., memory or a storage device); controlling peripheral devices (e.g., printers, external storage devices); and managing traffic on the one or more buses  514 . The network communications module  518  includes various components for establishing and maintaining network connections and services (e.g., software for implementing communication protocols and services, such as TCP/IP, HTTP, sync services, etc.). The login window system  522  includes various software components for displaying and managing the login window and related processes. The browser  520  allows the user to access the World Wide Web (WWW). 
     The portable computer account module  524  includes various software components (e.g., written in Objective-C or other known computer languages) for performing the portable computer account process  400 , as described in reference to  FIGS. 4A-4C . The portable computer account module  524  can include multiple software components or it can be a single body of code. 
     Various modifications may be made to the disclosed implementations and still be within the scope of the following claims.