Push away your privacy: Precise user tracking based on TLS client certificate authentication

Wachs, Matthias; Scheitle, Quirin; Carle, Georg

doi:10.23919/tma.2017.8002897

Cited by 13 publications

(12 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Wachs et al [42] suggest the use of TLS 1.3 as a solution to APNs client certificate privacy leakage by moving the CertificateRequest message until after the TLS encryption handshake has been completed, thereby obscuring fields that can be used to create cryptographically unique fingerprints of devices utilizing APNs. As a result, Apple implemented this client certificate obscuration feature of TLS 1.3 in TLS 1.2 using an application layer protocol extension.…”

Section: Apple Push Notification Client Servicementioning

confidence: 99%

“…Many people naïvely believe they are anonymous on the Internet, but researchers have repeatedly uncovered scenarios in which mobile devices transmit unencrypted, unique identifiers across a network [11,26,42]. When these identifiers are sent over the Internet, or even a local network, it makes tracking of the associated devices and correlation of their traffic possible.…”

Section: Introductionmentioning

confidence: 99%

“…Recent work by Wachs et al [42] identified a significant privacy risk [2] in the use of CCA in conjunction with Apple's Apple Push Notification service (APNs). Since client certificates are sent unencrypted to the server, exposing unique information within the client certificate, they can allow adversaries to identify users and/or profile their online behavior [42]. This attack was particularly alarming because it applied across the entire Apple ecosystem, and Apple makes up a large share of mobile devices currently in use.…”

Section: Introductionmentioning

confidence: 99%

“…Wachs et al [42] coordinated with Apple to fix the vulnerability they discovered and protect the privacy of APNs CCA by deferring the transmission of client certificates until after the TLS handshake. Additionally, Parsovs [35] and Johansson [24] have suggested extensions to TLS and modifications to client browsers to likewise protect the confidentiality of client certificates during CCA.…”

Section: Introductionmentioning

confidence: 99%

“…Internet Service Providers, from residential to Internet backbone Autonomous Systems, transit the client certificates of their customers; recent work suggests eavesdropping capabilities on less than a dozen networks globally allows the tracking of ∼80% of APNs messages. [42]…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Exploiting TLS Client Authentication for Widespread User Tracking

Foppe

Martin

Mayberry

et al. 2018

Proceedings on Privacy Enhancing Technologies

View full text Add to dashboard Cite

TLS, and SSL before it, has long supported the option for clients to authenticate to servers using their own certificates, but this capability has not been widely used. However, with the development of its Push Notification Service, Apple has deployed this technology on millions of devices for the first time. Wachs et al. [42] determined iOS client certificates could be used by passive network adversaries to track individual devices across the internet. Subsequently, Apple has patched their software to fix this vulnerability. We show these countermeasures are not effective by demonstrating three novel active attacks against TLS Client Certificate Authentication that are successful despite the defenses. Additionally, we show these attacks work against all known instances of TLS Client Certificate Authentication, including smart cards like those widely deployed by the Estonian government as part of their Digital ID program. Our attacks include in-path man-in-the-middle versions as well as a more powerful on-path attack that can be carried out without full network control.

show abstract

Section: Apple Push Notification Client Servicementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%