Secure Communications or the usability of PKI

Secure Communications … or, the usability of PKI

Agenda Announcement: Security Symposium on Oct. 10. n Questions? Stories to share? n Project discussion & IRB overview n Secure communications n

Project n n n Initial draft: 2 weeks Final plan: 4 weeks Initial draft is NOT graded, credit for reasonable effort – – n Some introduction, motivation, related work Draft of tasks, survey & interview questions, etc. Mockup or description if you are building something The more complete it is, the more feedback you’ll get! We will pilot your materials during class in 2 weeks (SO BRING YOUR MATERIALS TO CLASS!!!)

IRB http: //www. research. uncc. edu/comp/h uman. cfm n Download application form and consent form template n See Wiki for one sample application n

Public Key Infrastructure “A PKI is a set of agreed-upon standards, Certification Authorities (CA), structure between multiple CAs, methods to discover and validate Certification Paths, Operational Protocols, Management Protocols, Interoperable Tools and supporting Legislation” In other words: A Public Key Infrastructure is an Infrastructure to support and manage Public Key-based Digital Certificates “Digital Certificates” book – Jalal Feghhi, Jalil Feghhi, Peter Williams

Secure Communications n PKI: – What is your best technical explanation? – What is your best non-tech explanation? – How much should users be aware of keys? – What’s a CA? How to explain a CA? Should users be aware of CAs?

Communication under PKI n Both Alice and Bob have their own individual private and public keys signed by a certificate authority. – The CA might be an employer, Verisign, or some other organization.

Communication under PKI Bob’s public key Alice’s public key 0 11 0 10 n The public key is used for encryption and digital signature verification. n The private key is used for decryption and the creation of digital signatures.

Digital Signature

Digital Certificate A Digital Certificate is a binding between an entity’s Public Key and one or more Attributes relating its Identity. • The entity can be a Person, an Hardware Component, a Service, etc. • A Digital Certificate is issued (and signed) by someone - Usually the issuer is a Trusted Third Party • A self-signed certificate usually is not very trustworthy

X 509 PKI Trusted Root Alice trusts the root CA Bob sends a message to Alice needs Bob’s certificate, the certificate of the CA that signed Bob’s certificate, and so on up to the root CA’s self signed certificate. Alice also needs each CRL for each CA. * Alice Bob Only then can Alice verify that Bob’s certificate is valid and trusted and so verify the Bob’s signature. 11

Secure Communications n PKI: – What is your best technical explanation? – What is your best non-tech explanation? – How much should users be aware of keys? – What’s a CA? How to explain a CA? Should users be aware of CAs?

Problems with PKI n Public-key cryptography is counterintuitive. n PKI seems too far removed from application goals. – Users do not understand how their tasks require PKI. n PKI tasks are too cumbersome. n Large CAs run into naming collisions. – Users shoulder the burden of ensuring that the person they’re looking up is indeed the person they want.

IBM Lotus Notes & Domino Solution n n Client/server infrastructure for collaborative applications Usage of PKI – Authentication of Notes client to Domino Server – Signing and encrypting mail messages n Implementation – Note keys are created by Notes administrator and distributed to user in a “identity file” – Most of key management is hidden from user within the organization – Communicating outside the enterprise requires user input to acquire or verify certificates n Thoughts?

Alternative: i. PKI Lightweight PKI centered around a local, standalone CA • Automated PKI and CA setup • Simple, intuitive enrollment mechanism • A simple, intuitive trust model • Secure bootstrapping • Certificates as capabilities • No need for direct user interactions with certificates 15

Example: Network-in-a-box n Utilize location-limited channels to simplify configuration while maintaining security n Laptop and AP exchange public keys Use it to perform full-fledged security autoconfiguration n

i. PKI discussion Easier? n Secure enough? n What is it good for? n Limitations? n

Nia. B validation n Users study with 12? users – Task: connect to a secure wireless network, Nia. B or other – Results: Nia. B 10 x faster, fewer errors, more confidence and satisfaction n 2 nd study in an enterprise – Watched 5 users with each enrollment – Same results as before, but even bigger differences!

Alternative: Key Continuity Management n Goal: Make key generation & management easier to accomplish n Ignore the X. 509 certification chain Applications are directly aware of public key certificates User would be notified only when server’s key suddenly changes n n n Thoughts?

Johnny 2 n Study conducted on KCM – – – Closely followed the original Johnny study Same scenario, recruiting, descriptions, etc. Added additional attacks to examine user understanding and trust of keys – 43 subjects – 3 conditions: n n no KCM Color + briefing Question: study critique?

Results? n n KCM worked against New Key Attack KCM didn’t work against New Identity Attack – Users noticed the change, but felt it was justified n KCM really didn’t work against Unsigned Message Attack – users instead noticed they were being asked to send to hotmail and distrusted those instructions

Trust The encryption itself is not the problem n Trust required to make PKI work n – Did Alice really send this? n Is this the right Alice or another one? n Do I trust the certificate? n Do I trust the CA? n Do I trust that no one has taken over her computer? n At what point do I decide to not trust the message?