Data Protection API: Difference between revisions

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{{Short description|Windows API for cryptography}}

'''DPAPI (Data Protection Application Programming Interface)''' ('''DPAPI''') is a simple [[cryptography|cryptographic]] [[application programming interface]] available as a built-in component in [[Windows 2000]] and later versions of [[Microsoft Windows]] [[operating system]]s. In theory, the Data Protection API can enable symmetric encryption of any kind of data; in practice, its primary use in the Windows operating system is to perform symmetric encryption of asymmetric private keys, using a user or system secret as a significant contribution of entropy. A detailed analysis of DPAPI inner-workings was published in 2011 by [[Elie Bursztein|Bursztein]] et al.<ref>{{cite conference|lastlast1=Bursztein|firstfirst1=Elie|last2=Picod|first2=Jean Michel|date=2010|title=Recovering Windows secrets and EFS certificates offline|book-title=WoOT 2010|publisher=Usenix|url=https://elie.net/publication/recovering-windows-secrets-and-efs-certificates-offline/}}</ref>

For nearly all [[cryptosystem]]s, one of the most difficult challenges is "[[key management]]"{{snd}} in part, how to securely store the decryption key. If the key is stored in ''[[plain text]]'', then any user that can access the key can access the encrypted data. If the key is to be encrypted, another key is needed, and so on. DPAPI allows developers to encrypt keys using a symmetric key derived from the user's logon secrets, or in the case of system encryption, using the system's ___domain authentication secrets.

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Delegated access can be given to keys through the use of a [[COM+]] object. This enables [[Internet Information Services|IIS]] [[web servers]] to use DPAPI.

==Active Directory backup keys==

When a computer is a member of a ___domain, DPAPI has a backup mechanism to allow data deprotection in case the user's password is lost, which is named "Credential Roaming".

When installing a new ___domain on a ___domain controller, a public and private key pair is generated, associated with DPAPI.

When a master key is generated on a client workstation, the client communicates through an authenticated [[Remote procedure call|RPC]] call with a ___domain controller to retrieve a copy of the ___domain's public key. The client encrypts the master key with the ___domain controller's public key. Finally, it stores this new backup master key in its AppData directory, just like traditional master key storage.

==Use of DPAPI by Microsoft software==

While not universally implemented in all Microsoft products, the use of DPAPI by Microsoft products has increased with each successive version of Windows. However, many applications from Microsoft and third-party developers still prefer to use their own protection approach or have only recently switched to use DPAPI. For example, [[Internet Explorer]] versions 4.0–6.0, [[Outlook Express]] and [[MSN Explorer]] used the older Protected Storage (PStore) API to store saved credentials such as passwords etc. [[Internet Explorer&nbsp;7]] now protects stored user credentials using DPAPI.<ref>{{cite web | url=httphttps://wwwcommunity.symantecbroadcom.com/connectsymantecenterprise/articlescommunities/passwordcommunity-managementhome/librarydocuments/viewdocument?DocumentKey=cd572045-0dfe-4b49-concerns9df6-ie578cbc441ce5&CommunityKey=1ecf5f55-and9545-firefox44d6-partb0f4-one4e4a7f5f5e68&tab=librarydocuments | title=Password Management Concerns with IE and Firefox, part one | author=Mikhael Felker | date=December 8, 2006 | access-date=2010-03-28 | publisher=[[SecurityFocus.com]], [[Symantec.com]]}}</ref>

* Picture password, PIN and fingerprint in [[Windows 8]]

* [[Encrypting File System]] in Windows 2000 and later

* SQL Server [[Transparent Data Encryption]] (TDE) Service Master Key encryption<ref>{{cite web|url=https://msdn.microsoft.com/en-us/library/ms189586(v=sql.110).aspx|title=Encryption Hierarchy|website=Msdn.microsoft.com|date=April 2012 |access-date=14 October 2017}}</ref>

* [[Internet Explorer 7]], both in the standalone version available for [[Windows&nbsp;XP]] and in the integrated versions available in [[Windows Vista]] and [[Windows Server 2008]]

* [[Microsoft Edge]]

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* Windows [[Rights Management Services]] client v1.1 and later

* [[Windows 2000]] and later for [[Extensible Authentication Protocol#EAP-TLS|EAP/TLS]] ([[VPN]] authentication) and 802.1x ([[WiFi]] authentication)

* Windows XP and later for stored user names and passwords<ref>{{cite web|url=https://technet.microsoft.com/en-us/library/bb457059.aspx|title=What's New in Security for Windows XP Professional and Windows XP Home Edition|website=Technet.microsoft.com|date=11 September 2009 |access-date=14 October 2017}}</ref> (aka Credential Manager)

* [[.NET Framework 2.0]] and later for System.Security.Cryptography.ProtectedData<ref>{{cite web|url=http://msdn2.microsoft.com/en-us/library/system.security.cryptography.protecteddata.aspx|title=ProtectedData Class (System.Security.Cryptography)|website=Msdn2.microsoft.com|access-date=14 October 2017}}</ref>

* Microsoft.Owin (Katana) authentication by default when self-hosting (including cookie authentication and [[OAuth]] tokens)<ref>{{cite web|title=CookieAuthenticationOptions.TicketDataFormat Property (Microsoft.Owin.Security.Cookies)|url=http://msdn.microsoft.com/en-us/library/microsoft.owin.security.cookies.cookieauthenticationoptions.ticketdataformat(v=vs.113).aspx|access-date=2015-01-15}}</ref><ref>{{cite web|title=OAuthAuthorizationServerOptions.AccessTokenFormat Property (Microsoft.Owin.Security.OAuth)| date=27 October 2015 |url=http://msdn.microsoft.com/en-us/library/microsoft.owin.security.oauth.oauthauthorizationserveroptions.accesstokenformat(v=vs.113).aspx|access-date=2018-11-26}}</ref>

==References==

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==External links==

* [https://lestutosdeprocessus.fr/dechiffrement-dpapi.html Le fonctionnement de DPAPI par Processus Thief (FR)] {{Webarchive|url=https://web.archive.org/web/20221020071943/https://lestutosdeprocessus.fr/dechiffrement-dpapi.html |date=2022-10-20 }}

* [http://go.microsoft.com/fwlink/?LinkId=89993 Windows Data Protection API (DPAPI) white paper by NAI Labs]

* [http://www.codeproject.com/KB/system/protected_data.aspx Data encryption with DPAPI]