IE MS5710 E lectronic C ommunication and Online Social N etworks S ecurity

1. IEMS5710Electronic Communication and Online Social Networks Security 26 March2013 Prof. CHAN Yuen-Yan, Rosanna Department of Information Engineering The Chinese University of Hong Kong

2. Email Security and Privacy • Email communications is one of the earliest format of electronic communications. • Governments and organizations began adopting policies which effectively make email the preferred and official means of communication, making it equal to written (paper) communications in all respects. • Its security requirements (should) include: • Confidentiality: protection from disclosure • Authentication: of sender and receiver(s) of message • Message integrity: protection from modification • Non-repudiation of origin: protection from denial by sender (and receivers?) • SMTP (Simple Mail Transfer Protocol) has no security by default. Email message contents are not secure • may be inspected either in transit • or by suitably privileged users on destination system IEMS5710 - Lecture 10

3. Early Solution – PrettyGood Privacy (PGP) Developed by Phil Zimmermann in 1991 Used for email and file encryption Now developed into the OpenPGP standard (RFC 4880) IEMS5710 - Lecture 10

4. PGP encryption and decryption (Image from Wikipedia) IEMS5710 - Lecture 10

5. PGP Message Format ¥ denotes the corresponding plaintexts R64 = Radix 64 conversion (similar to ASCII codes) IEMS5710 - Lecture 10

6. PGP Key Management rather than relying on certificate authorities in PGP every user is own CA can sign keys for users they know directly forms a “web of trust” trust keys have signed can trust keys others have signed if have a chain of signatures to them key ring includes trust indicators users can also revoke their keys IEMS5710 - Lecture 10

7. PGP Trust Model Example IEMS5710 - Lecture 10

8. S/MIME (Secure/Multipurpose Internet Mail Extensions) security enhancement to MIME email original Internet RFC822 email was text only MIME provided support for varying content types and multi-part messages, with encoding of binary data to textual form S/MIME added security enhancements have S/MIME support in many mail agents eg MS Outlook, Mozilla, Mac Mail etc IEMS5710 - Lecture 10

9. S/MIME IEMS5710 - Lecture 10

10. S/MIME Functions enveloped data encrypted content and associated keys signed data encoded message + signed digest clear-signed data cleartext message + encoded signed digest signed & enveloped data nesting of signed & encrypted entities IEMS5710 - Lecture 10

11. S/MIME Cryptographic Algorithms digital signatures: DSS & RSA hash functions: SHA-1 & MD5 session key encryption: ElGamal & RSA message encryption: AES, Triple-DES, RC2-40bits and others MAC: HMAC with SHA-1 have process to decide which algorithms to use IEMS5710 - Lecture 10

12. S/MIME Certificate Processing S/MIME uses X.509 v3 certificates managed using a hybrid of a strict X.509 CA hierarchy & PGP’s web of trust each client has a list of trusted CA’s certs and own public/private key pairs & certs certificates must be signed by trusted CA’s IEMS5710 - Lecture 10

13. Internet Mail Architecture IEMS5710 - Lecture 10

14. Domain Keys Identified Mail IEMS5710 - Lecture 10 DomainKeys Identified Mail (DKIM) lets an organization take responsibility for a message while it is in transit a specification for cryptographically signing email messages so signing domain claims responsibility recipients / agents can verify signature Internet Standard RFC 4871

15. DKIM Strategy IEMS5710 - Lecture 10 • transparent to user • MSA sign • MDA verify

16. Security and Privacy in Social Network • (Ahn, Shehab, & Squicciarini, 2010) IEEE Internet Computing: Special Issue in Security & Privacy in Social Network • Most social networking sites offerthe basic features of online interaction,communication, and interest sharing; individuals create online profilesthat other users can view. • Special challenges to security & privacy • social networks involveuser-centric concerns and allow multiple usersto specify security policies on shared data • the increased risk to personal data processed by online social networking applications • the user population’s lack of awareness IEMS5710 - Lecture 10

17. Security and Privacy in Social Network • The privacy issue in social networkingis coupled with the identifiability andlinkability of the information availablein this social setting • Also include its possiblerecipients, and its potential uses • Social network sites enable users to create a limited profile and select which other users map to it • Such primitive security mechanisms have only limited expressiveness for controlling user-to-user interactions • Possiblerecipients for such personally identifiable information still include • hosting servers for the socialnetworking sites • the network itself, and • thirdparties that might abuse or misuse such criticaland sensitive information IEMS5710 - Lecture 10

18. Security Objectives on OSNs • (Cutillo et al., 2009) • OSN levels: three architectural layers of social networking services • Social network, application services, and communication and transport services IEMS5710 - Lecture 10

19. Security Objectives on OSNs • Three main security objectives are identified in the context of OSNs • Privacy • Integrity • Availability IEMS5710 - Lecture 10

20. Privacy • Privacy in OSNs encompasses the following • (user profile privacy) protection of personal information, which users publish on their profiles, presumably accessible by their contacts only • (communication privacy)none but directly addressed orexplicitly trusted parties may have the possibilityto trace which parties are communicating • (message confidentiality)details of messages have to be hidden,so only the requesting and responding partiesshould know one another’s identity and the contentof the request • (Information disclosure)disclosure of informationabout a member to some parties that are not explicitly trusted, withoutthe consent of the member, has to be prevented IEMS5710 - Lecture 10

21. Privacy • In principle, privacy calls for the possibilityto hide any information about any user, even tothe extent of hiding their participation in theOSN in the first place • Moreover privacy has tobe met by default • all information on allusers and their actions has to be hidden fromany other party internal or external to the system,unless explicitly disclosed by the usersthemselves • Requiring explicit disclosure leads tothe need for access control. • Access to informationon a user may only be granted by the userdirectly • the access control has to be as finegrainedas the profile, and each attribute has tobe separately manageable IEMS5710 - Lecture 10

22. Integrity • As part of integrity, the user’s identity and datamust be protected against unauthorized modificationand tampering • In addition to conventionalmodification detection and messageauthentication, integrity in the context of OSNshas to be extended: • E.g. parties in an OSN are notarbitrary devices, but real, unambiguously identifiablepersons • However, the creation of personae —bogus accounts, cloned accounts, or other typesof impersonation — in traditional social networks is easy toachieve • Therefore, the authenticationhas to ensure the existence of real personsbehind registered OSN members IEMS5710 - Lecture 10

23. Availability • Since some social network services are used as professional tools toaid their members’ business or careers, datapublished by users has to be continuously available • Availability of user profiles is consequentlyrequired as a basic feature, even though consideringrecreational use • In OSNs, this availability specifically has toinclude robustness against censorship, and theseizure or hijacking of names and other keywords • Apart from availability of data access,availability has to be ensured along with messageexchange among members IEMS5710 - Lecture 10

24. Security Model of OSNs • Social Network Services (SNS) can be divided into three different levels (Cutillo et al., 2009, p.5): • A social network (SN) level: The digitalrepresentation of members and their relationships; provides each member with aset of functions corresponding to social interactionsin the real life • An application services (AS) level: Theapplication infrastructure, managed by theSNS provider • A communication and transport (CT) level:Communication and transport services asprovided by the network IEMS5710 - Lecture 10

25. Security Model of OSNs • Two kinds of attackers in OSNs: inside attackers and external attackers • An inside attacker primarilyseem to be legitimate participants in the system, can be one of the following: • A malicious member on the SN level • A malicious service provider on the ASlevel • A party that has and misuses access to theinfrastructure at the CT level (e.g. an eavesdropperwith a local view, or a malicious ISPwith possibly even a global view) • External attackers, or intruders, can perpetrate attacks at one or moreof the SNS levels IEMS5710 - Lecture 10

26. Social Network Data (Schneier, 2010) • A taxonomy was presented by Bruce Schneier (famous security researcher) at OECD (经济合作与发展组织) • Define user data in social network sites from security & privacy perspectives • 6 types of data • Service data • Disclosed data • Entrust data • Incidental data • Behavioral data • Derived data IEMS5710 - Lecture 10

27. Social Network Data (Schneier, 2010) • Service data is the data you giveto a social networking site in orderto use it. • Such data might includeyour legal name, your age,and your credit-card number. • Disclosed data is what you poston your own pages • E.g. blog entries,photographs, messages, comments,and so on. • Entrusted data is what you poston other people’s pages. • It’s basicallythe same stuff as discloseddata, but the difference is thatyou don’t have control over thedata once you post it—anotheruser does. IEMS5710 - Lecture 10

28. Social Network Data (Schneier, 2010) • Incidental datais what other people post about you: a paragraph about you that someone else writes, a picture of you that someone else takes and posts • Again, it’s basically the same stuff as disclosed data, but the difference is that you don’t have control over it, and you didn’t create it in the first place. • Behavioral data is data the sitecollects about your habits by recordingwhat you do and whoyou do it with. • It might includegames you play, topics you writeabout, news articles you access(and what that says about yourpolitical leanings), and so on. • Derived data is data about youthat is derived from all the otherdata. • For example, if 80 percentof your friends self-identify as Christian, you’re likely Christian yourself. IEMS5710 - Lecture 10

29. Social Network Data (Schneier, 2010) • As a user, you may have the following perspectives about data privacy when you submit your data • Some of it you give to a social networking site in confidence, expecting the site to safeguard the data. • Some of it you publish openly and others use it to find you. • Some of it you share only within an small circle of other users. • However, at the receiving end, technically, the social networking sites can monetize all of it: generally by selling targeted advertising. • Different social networking sites give users different rights for each data type. • Some are always private, some can be made private, and some are always public. • Some can be edited or deleted, e.g. some sites allow entrusted data to be edited or deleted within a 24-hour period, and some cannot. • Some can be viewed and some cannot. IEMS5710 - Lecture 10

30. Social Network Data (Schneier, 2010) • User’s right about behavioral data is even more controversial • It’s frequently a critical part of a social networking site’s business model. Users should have different rights with respect to each data type. • We often don’t mind if a site uses it to target advertisements, but are less confident when it sells data to third parties. • We should be allowed to export, change, and delete disclosed data • even if the social networking sites don’t want us to. • But it’s less clear what rights we have for incidental data • E.g. If someone post pictures from a party with you in them, can you demand him/her remove those pictures—or at least blur out your face? • It is still debatable about what sorts of fundamental rights people have with respect to their data on social networks • more countries may contemplate regulation of social networking sites and user data • For security and privacy on social network, it is important to keep this taxonomy in mind. • The sorts of things that would be suitable for one type of data might be completely unworkable and inappropriate for another. IEMS5710 - Lecture 10

31. Social Network Connect Service (reviewed by Ko et al., 2010) • Social-networks connect services (SNCSs) • supported in major social-networking sites such as Facebook Platform, Google Friend Connect, and MySpaceID • let third-party sites develop social applications and extend their services without having to either host or build their own social network • This extension allows third-party sites to leverage the social-networking site’s features • E.g. third-party sites can exploit the authentication services provided by a social-networking site so that users need not create another username and password to access the third-party site IEMS5710 - Lecture 10

32. Social Network Connect Service Framework • For social-networking sites to be able to share user Social Web data with third-party sites, a secure and reliable SNCS framework is required IEMS5710 - Lecture 10

33. SNCS Framework: User Data • Under the SNCS framework, user data is composed of three types of information • Identity datadescribes who I am in the Social Web, including my identity, profile information, and privacy policy • Social-graph datarepresents who I know in the Social Web, including my friendship connections with descriptions such as family, co-worker, colleague, and so on • Content datarepresents what I have in the Social Web, including my messages, photos, videos, and all other data objects created through various Social Web activities IEMS5710 - Lecture 10

34. SNCS Framework • Four categories of APIs that allow third-party sites to interface with the social-networking site • Identity authenticationproves users’ identity; users can authenticate using their existing accounts from various identity providers to include the social-networking site • Authorizationgoverns access to user data in the Social Web based on pre- defined authorization access rights; the authorization API lets third-party sites create new content and extract existing content from users’ Social Web data • Streams let third-party sites publish to users’ activity streams and vice versa • Applications let third-party sites develop rich social features in the form of applications and thereby extend the Social Web • The implementation of these APIs can vary widely with different protocols and technologies IEMS5710 - Lecture 10

35. Example: Facebook Platform • Facebook Platform lets third-party sites integrate with Facebook and send information both ways • to create more engaging and richer social experiences on the Web • Facebook Platform allows users to export their identity, profile, privacy policy, social graph, and content from Facebook to third-party sites • Authentication is by far the most used Facebook Platform component. This API enables third-party sites to leverage Facebook as an identity provider IEMS5710 - Lecture 10

36. Facebook Platform • Facebook platform service IEMS5710 - Lecture 10

37. Facebook Platform • Example: Digg.com doesn’t require new members to register and create a profile. Instead, they can use their existing Facebook profile to authenticate IEMS5710 - Lecture 10

38. OAuth 2.0 and Facebook Platform Authentication • Facebook Platform leverages OAuth 2.0 for authentication and authorization • OAuth is an open standard for authorization, OAuth 2.0 is evolved from OAuth (not backwards compatible) and the specification is being developed by the IETF • But unlike OAuth 1.0, OAuth 2.0 doesn't support signature, encryption, channel binding, or client verification. It relies completely on SSL for some degree of confidentiality and server authentication. • Facebook supports OAuth 2.0 and is the largest implementation of the emerging standard • First, a user of the third-party site authenticates using Facebook as an identity provider • Next, Facebook issues a user access tokenthat lets the third-party site access the user’s basic profile information including name, picture, gender, and Friend List • The third-party site can request extended permissions depending on the specific application requirements IEMS5710 - Lecture 10

39. Challenges for SNCSs • The Social Web is growing exponentially due to SNCSs, but with this growth come several challenges, most pertaining to security and privacy • Challenges discussed by Ko et al. (2010) include • Identity mapping • User data portability • Common enhanced privacy policy framework • Cascaded authorization • Data integrity in social plug-ins • Also notice that Eran Hammer resigned his role of lead author for the OAuth 2.0 project, withdrew from the IETF working group, and removed his name from the specification. Hammer pointed to a conflict between the web and enterprise cultures • huniverse: OAuth 2.0 and the Road to Hell IEMS5710 - Lecture 10

40. Privacy Breach Attacks (Gao et. al., 2011) • A study on the Facebookusers in the Carnegie Mellon Universitynetwork reveals: • 90.8% uploaded their images • 87.8% revealed their birth dates • 39.9% shared their phone numbers • 50.8% listed their currentaddresses • Abundance of readily available personal information makesprivacy breach a unique angle of attack in social networks • Three primary parties interact with oneanother in an OSN: • the service provider, theusers, and third-party applications IEMS5710 - Lecture 10

41. Breaches from Service Providers • OSNs’ current client–server architecture inherentlydictates that users must trust service providersto protect all the personal informationthey’ve uploaded • However, service providerscan obviously benefit from examining andsharing this information • E.g. for advertising purposes IEMS5710 - Lecture 10

42. Breaches from Service Providers • E.g. TheFacebook “Statement of Rights andResponsibilities”requires that users “not provide any false personal informationon Facebook” • and “keep [their] contact information accurateand up to date.” • Further, it states that users “grant [Facebook] a non-exclusive, transferable, sub-licensable, royalty-free, worldwide license to use any IP [Intellectual Property]content that [they] post on or in connection with Facebook“ • Facebook “Statement of Rights andResponsibilities” • https://m.facebook.com/legal/terms/?_rdr IEMS5710 - Lecture 10

43. Examples of Secured Social Networks (Persona) • Persona: allowing users to apply fine-grained policies over who may view their data • puts policy decisions in the hands of the users • uses decentralized, persistent storage so that users may choose with whom they store their information • Supports both public-key cryptography(to share information with any single entity inthe network) and attribute-based encryption (ABE) (toshare content with entire groups) IEMS5710 - Lecture 10

44. Examples of Secured Social Networks (Persona) • Attribute-based encryption (ABE): • For each friend, the user can generate an ABE secret key (ASK) corresponding to the set of attributes that defines the groups that friend should be part of • Each encryption must specify an access structure: a logical expression over attributes. • For instance,Alice can choose to encrypt a message with access structure (‘neighbor’ OR ‘football fan’), where ‘neighbor’ and ‘football fan’ are attributes, and anyof her friends who have an attribute secret key with eitherattribute will be able to decrypt the message • Alice can alsoencrypt to (‘neighbor’ AND ‘football fan’).In this case, theABE construction ensures that only friends with both attributes will be able to decrypt the message IEMS5710 - Lecture 10

45. Examples of Secured Social Networks (Lockr) • http://research.microsoft.com/en-us/projects/lockr/ • Lockr separates social networkcontent from social network functionalities. • Lets users decide where to store their informationwithout interrupting the social network functionalities • In Lockr, the recipient of digitally signedsocial relationships can provide these signedsocial relationships to the social network service providers as proof tofetch social data • also ensures that the social network service providers can’t reuse the signed social relationshipsfor unintended purposes • Lockr enables message encryption using a social relationship key. IEMS5710 - Lecture 10

46. Examples of Secured Social Networks • (Anderson et al., 2009) • Researchers have also proposed an OSN architecture consisting ofsmart clients and an untrusted central server • The server stores encrypted data so that it’savailable only for those who have been grantedaccess to it IEMS5710 - Lecture 10

47. Breaches from Other Users • Major OSNs let a user’sfriends access the personal information the userhas uploaded to his or her profile by default,while blocking others from doing so • However,the notion of “friends” here is merely asocial link that the two users have agreed toestablish, regardless of the actualoffline relationship • This discrepancy providesa potential channel for stealing personal informationby befriending users in OSNs IEMS5710 - Lecture 10

48. Breaches from Other Users • Same-site profile cloning • An attacker duplicates a user’s profile in thesame social network and uses the duplication to send outfriend requests to the user’s friends • Believingthe request has come from a familiar person,the unalerted friends can accept it andthereby expose their personal information tothe attacker • Cross-site profile cloning • The attacker identifies a user from social network A (SN A),along with this user’s friend list • The attackerthen duplicates the profile to SN B, where theuser hasn’t yet registered, and sends out friendrequests on OSN B to the target’s friends whohave also registered on OSN B • Cross-site profilecloning is potentially more dangerous thansame-site cloning because it’s less likely toarouse suspicion IEMS5710 - Lecture 10

49. Breaches from Third-Party Applications • There exists many applicationsreside on the social network platform but were developed by third party, which are essentially untrusted • E.g. Facebook applications and Google’s OpenSocial IEMS5710 - Lecture 10

50. Breaches from Third-Party Applications • Users must grant theapplication access to their personal data beforethey can install those applications • such access is necessary for some applicationsto perform their functionality (e.g. ahoroscope application must know the user’sbirthday) • Unfortunately, neither the service providernor the users know exactly which piece of informationis truly necessary for the applications • The current approachis to legally bind the third parties using a Termsof Service (TOS) agreement. • However, there is no mechanism to monitor how theapplications manipulate the personal information collected • This leaves the door open forthe applications to misuse that information IEMS5710 - Lecture 10