编辑“︁BitLocker”︁（章节）

== 安全问题 ==
据微软透露<ref>{{cite web|url=http://blogs.msdn.com/si_team/archive/2006/03/02/542590.aspx|title=Back-door nonsense|accessdate=|date=2006-03-02|last=|first=|work=System Integrity Team Blog|publisher=Microsoft|archive-url=https://web.archive.org/web/20100209023432/http://blogs.msdn.com/si_team/archive/2006/03/02/542590.aspx|archive-date=2010-02-09|deadurl=yes}}</ref>，BitLocker没有刻意设置[[軟體後門|后门]]。没有后门，执法机构就无法从安全通道获取微软提供的用户驱动器上的数据。2006年，[[英國內政部|英国内政部]]担心缺乏后门<ref>{{cite news|url=http://news.bbc.co.uk/1/hi/uk_politics/4713018.stm|title=UK holds Microsoft security talks|last=Stone-Lee|first=Ollie|date=2006-02-16|publisher=[[英国广播公司|BBC]]|accessdate=2009-06-12|archive-date=2009-03-18|archive-url=https://web.archive.org/web/20090318144355/http://news.bbc.co.uk/1/hi/uk_politics/4713018.stm|dead-url=no}}</ref>，试图与微软谈判，微软开发人员{{le|尼尔斯·弗格森|Niels Ferguson}}和其他微软的发言人表示他们不会增加后门<ref>{{cite web|url=http://news.cnet.com/Microsoft-Vista-wont-get-a-backdoor/2100-1016_3-6046016.html|title=Microsoft: Vista won't get a backdoor|accessdate=2008-05-01|date=2006-03-03|last=Evers|first=Joris|work=CNET|publisher=CBS Interactive|archive-date=2011-06-16|archive-url=https://web.archive.org/web/20110616161547/http://news.cnet.com/Microsoft-Vista-wont-get-a-backdoor/2100-1016_3-6046016.html|dead-url=no}}</ref>。微软工程师曾表示，虽然没有正式的书面请求，[[联邦调查局]]特工也在许多会议上向他们施加压力，要求增加后门。微软的工程师最终向FBI建议，特工应该寻找BitLocker程序建议其用户创建的密钥{{le|硬拷贝|Hard copy}}<ref>{{Cite web|url=http://mashable.com/2013/09/11/fbi-microsoft-bitlocker-backdoor/|title=Did the FBI Lean On Microsoft for Access to Its Encryption Software?|last=Franceschi-Bicchierai|first=Lorenzo|website=Mashable|access-date=2016-10-07|archive-date=2016-10-07|archive-url=https://web.archive.org/web/20161007083233/http://mashable.com/2013/09/11/fbi-microsoft-bitlocker-backdoor/|dead-url=no}}</ref>。虽然BitLocker使用的AES加密算法属[[公有领域]]，但它在BitLocker以及软件的其他组件中的实现都是[[专有软件|专有的]]。该代码可供微软合作伙伴和企业审查，但须遵守[[保密协议]]。<ref>{{Cite news|url=https://www.petri.com/no-back-doors-microsoft-opens-windows-source-code-to-eu-governments|title=No Back Doors: Microsoft Opens Windows Source Code to EU Governments – Petri|last=Thurrott|first=Paul|date=2015-06-10|work=|newspaper=Petri|language=|access-date=2016-10-07|via=|archive-date=2017-02-22|archive-url=https://web.archive.org/web/20170222104448/https://www.petri.com/no-back-doors-microsoft-opens-windows-source-code-to-eu-governments|dead-url=yes}}</ref><ref>{{Cite web|url=https://www.microsoft.com/en-us/sharedsource/|title=Shared Source Initiative|last=Microsoft|first=|date=|website=www.microsoft.com|publisher=|access-date=2016-10-07|archive-date=2018-09-28|archive-url=https://web.archive.org/web/20180928191411/https://www.microsoft.com/en-us/sharedsource/|dead-url=no}}</ref>

BitLocker的“透明运行模式”和“用户认证模式”使用[[可信平台模块|TPM]]硬件检测[[BIOS]]和[[主引导记录|MBR]]预加载环境是否有未经授权的改变。如果检测到任何未经授权的更改，BitLocker将在USB设备上请求一个恢复密钥。该加密密钥用于解密卷主密钥，并允许继续运行[[啟動程式|引导]]过程<ref name="TPM-operation2">{{cite journal|title=Keys to Protecting Data with BitLocker Drive Encryption|url=http://www.microsoft.com/technet/technetmag/issues/2007/06/BitLocker|last=Byron|first=Hynes|publisher=Microsoft|accessdate=2007-08-21|work=TechNet Magazine|journal=|archive-date=2007-09-03|archive-url=https://web.archive.org/web/20070903150307/http://www.microsoft.com/technet/technetmag/issues/2007/06/BitLocker/|dead-url=no}}</ref>。

2008年2月，一个安全研究小组发布了所谓“[[冷启动攻击]]”的详细信息，其通过将机器从可移动介质（如USB驱动器）引导到另一个操作系统，然后[[核心转储|转储]]预引导内存中的内容来损害诸如BitLocker的全磁盘加密系统<ref name="ColdBoot2">{{cite thesis|url=http://citp.princeton.edu/pub/coldboot.pdf|title=Lest We Remember: Cold Boot Attacks on Encryption Keys|last1=Halderman|first1=J. Alex|last2=Schoen|first2=Seth D.|last3=Heninger|first3=Nadia|last4=Clarkson|first4=William|last5=Paul|first5=William|last6=Calandrino|first6=Joseph A.|last7=Feldman|first7=Ariel J.|last8=Appelbaum|first8=Jacob|last9=Felten|first9=Edward W|publisher=[[普林斯顿大学|Princeton University]]|format=PDF|date=2008-02-21|journal=|year=|volume=|pages=|via=|archive-url=https://web.archive.org/web/20110904213748/http://citp.princeton.edu/pub/coldboot.pdf|archive-date=2011-09-04|access-date=2017-07-02|dead-url=yes}}</ref>。攻击依赖于这样一个事实：电源关闭后，[[DRAM]]会{{le|数据残留|Data remanence|保留}}长达数分钟的信息（冷却后的保留时间更长）。美国专利9,514,789号描述的Bress/ Menz装置可以完成这种攻击<ref>{{cite web|url=http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&co1=AND&d=PTXT&s1=bress.INNM.&s2=menz.INNM.&OS=IN/bress+AND+IN/menz&RS=IN/bress+AND+IN/menz|title=Systems and methods for safely moving short term memory devices while preserving, protecting and examining their digital data|website=USPTO.gov|access-date=2017-04-01|archive-date=2018-09-19|archive-url=https://web.archive.org/web/20180919025131/http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&co1=AND&d=PTXT&s1=bress.INNM.&s2=menz.INNM.&OS=IN%2Fbress+AND+IN%2Fmenz&RS=IN%2Fbress+AND+IN%2Fmenz|dead-url=no}}</ref>。单独使用[[可信平台模块|TPM]]不会提供任何保护，因为Windows运行时密钥保存在内存中。其他供应商和操作系统（包括[[Linux]]和[[Mac OS X]]）的类似全磁盘加密机制也容易遭受同样的攻击。[[普林斯顿大学]]教授的一篇论文推荐在未取得拥有者物理控制的情况下应将计算机关闭而不是处于[[睡眠模式]]，并且把加密软件配置为需要密码才能启动机器<ref name="ColdBoot2" />。

一旦受BitLocker保护的机器开始运行，其密钥就会存储在内存中，可能易受能够访问物理内存的进程的攻击，例如通过[[IEEE 1394|1394]]或[[Thunderbolt]] [[直接記憶體存取|DMA]]通道攻击<ref>{{cite web|url=http://support.microsoft.com/kb/2516445|title=Blocking the SBP-2 driver and Thunderbolt controllers to reduce 1394 DMA and Thunderbolt DMA threats to BitLocker|accessdate=2011-03-15|date=2011-03-04|publisher=Microsoft|archive-date=2012-08-13|archive-url=https://www.webcitation.org/69sS3DtU7?url=http://support.microsoft.com/kb/2516445|dead-url=no}}</ref>。从Windows 10版本1803开始，微软向BitLocker添加名为“内核DMA保护”的新功能，可防止通过[[Thunderbolt 3]]端口进行的DMA攻击<ref>{{cite web |url=https://docs.microsoft.com/en-us/windows/security/information-protection/kernel-dma-protection-for-thunderbolt |title=Kernel DMA Protection for Thunderbolt™ 3 |publisher=Microsoft |date=2019-03-26 |access-date=2020-03-16 |archive-date=2020-04-22 |archive-url=https://web.archive.org/web/20200422022727/https://docs.microsoft.com/en-us/windows/security/information-protection/kernel-dma-protection-for-thunderbolt |dead-url=no }}</ref>。

最初，Windows Vista使用AES的密码块链接（CBC）+大象扩散器（Elephant Diffuser）模式进行磁盘加密<ref>[http://www.ecice06.com/CN/article/downloadArticleFile.do?attachType=PDF&id=21245 梁敏, 常朝稳, 樊雪竹. 加密存储算法和模式研究] {{Wayback|url=http://www.ecice06.com/CN/article/downloadArticleFile.do?attachType=PDF&id=21245 |date=20200503153546 }} Research of Encryption Storage Algorithms and Modes[J]. 计算机工程, 2011, 037(013):101-103.</ref>。自Windows 8和Windows Server 2012开始，微软在没有声明原因的情况下从BitLocker方案中移除了大象扩散器（Elephant Diffuser），仅使用CBC模式进行磁盘加密<ref>{{Cite web|url=https://technet.microsoft.com/en-us/library/hh831713.aspx|title=BitLocker Overview|website=technet.microsoft.com|access-date=2016-10-07|archive-date=2017-02-13|archive-url=https://web.archive.org/web/20170213185949/https://technet.microsoft.com/en-us/library/hh831713.aspx|dead-url=no}}</ref>。软件工程师丹·罗森多夫（Dan Rosendorf）的研究表明，移除大象扩散器对BitLocker加密的安全性有“不可否认的负面影响”<ref>{{Cite web|url=http://spi.unob.cz/presentations/23-May/07-Rosendorf%20The%C2%A0BitLocker%C2%A0Schema.pdf|title=Bitlocker: A little about the internals and what changed in Windows 8|date=2013-05-23|last=Rosendorf|first=Dan|publisher=|archiveurl=https://web.archive.org/web/20160522145507/http://spi.unob.cz/presentations/23-May/07-Rosendorf%20The%C2%A0BitLocker%C2%A0Schema.pdf|archivedate=2016-05-22|website=|access-date=2016-10-07|deadurl=yes}}</ref>。微软随后说明扩散器移除的原因是性能问题以及不遵守[[联邦信息处理标准]]（FIPS）<ref>{{Cite web|url=https://theintercept.com/2015/06/04/microsoft-disk-encryption/|title=Microsoft Gives Details About Its Controversial Disk Encryption|date=2015-06-04|last=Lee|first=Micah|publisher=|website=The Intercept|access-date=2016-10-07|archive-date=2018-10-03|archive-url=https://web.archive.org/web/20181003050637/https://theintercept.com/2015/06/04/microsoft-disk-encryption/|dead-url=yes}}</ref>。从Windows 10版本1511开始，微软向BitLocker添加了新的符合FIPS标准的{{le|磁盘加密理论|Disk encryption theory|XTS-AES}}加密算法<ref name=":0" />。

2015年11月10日，微软发布了一项安全更新，修补BitLocker中的安全漏洞。漏洞使攻击者可以绕过目标计算机上的[[Kerberos]]身份验证，只有在计算机已加入域，目标系统已启用BitLocker且没有[[PIN]]或USB密钥的情况下，才能利用该绕过漏洞<ref>{{cite web|url=https://technet.microsoft.com/library/security/MS15-122|title=Microsoft Security Bulletin MS15-122 – Important|accessdate=2015-11-12|date=2015-11-10|work=Security TechCenter|publisher=[[微软|Microsoft]]|archive-date=2016-02-24|archive-url=https://web.archive.org/web/20160224173106/https://technet.microsoft.com/library/security/MS15-122|dead-url=no}}</ref>。