CSE 543 Computer Security: Risks of PKI - Josh Schiffman & Archana Viswanath

Ten Risks of PKI:What You're not Being Told about

Public Key Infrastructure

Joshua SchiffmanArchana Viswanath

CSE 543 Computer Security: Risks of PKI - Josh Schiffman & Archana Viswanath

Computer Security

● Security is a business○ Especially PKI

● PKI needs business to thrive○ Buy certificates○ PKI equipment

● Certificates are the commodity○ How trustworthy are they?

CSE 543 Computer Security: Risks of PKI - Josh Schiffman & Archana Viswanath

Categories of Risk

● Security is a chain○ Only as strong as the weakest link

● We identify three main categories for risk○ Trust in the Certification Authority (CA)○ Trust in the encryption keys○ Trust in the users

CSE 543 Computer Security: Risks of PKI - Josh Schiffman & Archana Viswanath

Certification Authorities

● PKI requires distribution of public keys○ Dangerous to send in the clear

● CAs provide certificates binding name to key○ What makes a CA trusted?○ What guarantee do we have the certificate is real?

Alice CA

KB

Really? This is Bob'spublic key

CSE 543 Computer Security: Risks of PKI - Josh Schiffman & Archana Viswanath

Content Authorities

● Certificates contain more than just a key○ Name / ID○ DNS for SSL

● Who is authorized to provide this content○ CAs are not authorities○ Contrary to many other systems

▶ Business name▶ Licenses

● Does it always matter?○ Offers no added encryption

CSE 543 Computer Security: Risks of PKI - Josh Schiffman & Archana Viswanath

Registration Authority

● Registration Authorities (RA)○ Authority on the contents○ Establish secure communication with the CA

● What guarantees are in the RA+CA model?○ CAs can forge certificates○ More vectors for attack○ Authorities physically possessing the CA helps

▶ Breaks some business models

CSE 543 Computer Security: Risks of PKI - Josh Schiffman & Archana Viswanath

Identifying the Applicant

● Does the CA verify applications?○ Identity checking○ Are the credentials easy to obtain?

● Is there private key verification?○ Possessing the public key for the certificate

▶ Does not prove possession of private key

Alice CA

KA

Really?This is mypublic key

CSE 543 Computer Security: Risks of PKI - Josh Schiffman & Archana Viswanath

Securing the CA

● CAs don't keep secrets○ All verification is done with public keys

● Use “root certificates" to vouch for the certificate○ Self-signed○ Form a chain of trust

▶ Must end at some ultimately trusted party

● Attackers can inject their own root keys○ Spoof public keys

● Physically protect the CA