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Development of a comprehensive legal privacy framework in the United States should be based on identification of the common deficiencies of privacy policies. We attempt to delineate deficiencies by critically analyzing the privacy policies of mobile apps, application suites, social networks, Internet Service Providers, and Internet-of-Things devices. Whereas many studies have examined readability of privacy policies, few have specifically identified the information that should be provided in privacy policies but is not. Privacy legislation invariably starts a definition of personally identifiable information. We find that privacy policies’ definitions of personally identifiable information are far too restrictive, excluding information that does not itself identify a person but which can be used to reasonably identify a person, and excluding information paired with a device identifier which can be reasonably linked to a person. Legislation should define personally identifiable information to include such information, and should differentiate between information paired with a name versus information paired with a device identifier. Privacy legislation often excludes anonymous and de-identified information from notice and choice requirements. We find that privacy policies’ descriptions of anonymous and de-identified information are far too broad, including information paired with advertising identifiers. Computer science has repeatedly demonstrated that such information is reasonably linkable. Legislation should define these categories of information to align with technological abilities. Legislation should also not exempt de-identified information from notice requirements, to increase transparency. Privacy legislation relies heavily on notice requirements. We find that, because privacy policies’ disclosures of the uses of personal information are disconnected from their disclosures about the types of personal information collected, we are often unable to determine which types of information are used for which purposes. Often, we cannot determine whether location or web browsing history is used solely for functional purposes or also for advertising. Legislation should require the disclosure of the purposes for each type of personal information collected. We also find that, because privacy policies disclosures of sharing of personal information are disconnected from their disclosures about the types of personal information collected, we are often unable to determine which types of information are shared. Legislation should require the disclosure of the types of personal information shared. Finally, privacy legislation relies heavily on user choice. We find that free services often require the collection and sharing of personal information. As a result, users often have no choices. We find that whereas some paid services afford users a wide variety of choices, paid services in less competitive sectors often afford users few choices over use and sharing of personal information for purposes unrelated to the service. As a result, users are often unable to dictate which types of information they wish to allow to be shared, and which types they wish to allow to be used for advertising. Legislation should differentiate between take-it-or-leave it, opt-out, and opt-in approaches based on the type of use and on whether the information is shared. Congress should consider whether user choices should be affected by the presence of market power.
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UDM: Private User Discovery with Minimal Information Disclosure
We present and analyze UDM, a new protocol for user discovery in anonymous communication systems that minimizes the information disclosed to the system and users. Unlike existing systems, including those based on private set intersection, UDM learns nothing about the contact lists and social graphs of the users, is not vulnerable to off-line dictionary attacks that expose contact lists, does not reveal platform identifiers to users without the owner’s explicit permission, and enjoys low computation and communication complexity. UDM solves the following user-discovery problem. User Alice wishes to communicate with Bob over an anonymous communication system, such as cMix or Tor. Initially, each party knows each other’s public contact identifier (e.g., email address or phone number), but neither knows the other’s private platform identifier in the communication system. If both parties wish to communicate with each other, UDM enables them to establish a shared key and learn each other’s private platform identifier. UDM uses an untrusted user-discovery system, which processes and stores only public information, hashed values, or values encrypted with keys it does not know. Therefore, UDM cannot learn any information about the social graphs of its users. Using the anonymous communication system, each pair of users who wish to communicate with each other uploads to the user-discovery system their private platform identifier, encrypted with their shared key. Indexing their request by a truncated cryptographic hash of their shared key, each user can then download each other’s encrypted private platform identifier.
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- Award ID(s):
- 1753681
- PAR ID:
- 10160119
- Date Published:
- Journal Name:
- Cryptologia
- ISSN:
- 1558-1586
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Conference Paper:
- The DOI is not currently available.
