The Battle Against Phishing:Dynamic Security Skins

Rachna Dhamija and J.D. TygarU.C. Berkeley

Security Properties for Usability

1. Limited human skills property

2. Unmotivated users property

3. General purpose graphics property

4. Golden arches property

5. Barn door property

Security Properties for Usability

1. Limited human skills property

2. Unmotivated users property

3. General purpose graphics property

4. Golden arches property

5. Barn door property

Limited Human Skills Property

• Limited password recall • Hard to parse domain names

Security Properties for Usability

1. Limited human skills property

2. Unmotivated users property1. Security is often the secondary goal

3. General purpose graphics property

4. Golden arches property

5. Barn door property

Users Don’t Check Certificates

Security Properties for Usability

1. Limited human skills property

2. Unmotivated users property

3. General purpose graphics property

4. Golden arches property

5. Barn door property

Firefox Browser: 4 SSL indicators

Firefox browser - No unsecure indicators

Security Properties for Usability

1. Limited human skills property

2. Unmotivated users property

3. General purpose graphics property

4. Golden arches property1. Train users not to automatically trust a logo or brand

5. Barn door property

The golden arches property

Security Properties for Usability

1. Limited human skills property

2. Unmotivated users property

3. General purpose graphics property

4. Golden arches property

5. Barn door property

Strong Password Protocols

• Stanford Web PwdHash

• Password Authenticated Key Agreement– EKE, SPEKE, SNAPI, AuthA, PAK, SRP, etc…

H(password, siteID)Password

ProtocolPassword

Password Authenticated Key Agreement

• Advantages:– preserve familiar use of passwords

• user doesn’t need a trusted device• secret stored in memory of the user

– server doesn’t store password– no passwords sent over the network– user authentication (& mutual authentication)

• But how to enter the password?

Our Solution: Usability Goals

• User must be able to verify password prompt, before entering password

• Rely on human skills– To login, recognize 1 image & recall 1 password– To verify server, compare 2 images

• Hard to spoof security indicators

Trusted Password Window

• Dedicated window • Trusted path customization• Random photo assigned or chosen• Image stored in browser, do not have

to go through server• Image overlaid across window • User recognizes image first

– then enters password

• Password not sent to server

Security Indicators

• How can user distinguish secure windows?– Static indicators (SSL)

• Can be spoofed• User do not really examine it

– User customized indicators (Passmark/Petnames)• Require extra efforts from the user

– Automated customized indicators

Our Solution: Dynamic Security Skins

Automatically customize secure windows

Visual hashes– Random Art - visual hash algorithm – Generate unique abstract image for each authentication– Use the image to “skin” windows or web content– Browser generated or server generated

Browser Generated Images

Browser chooses random number and generates image Can be used to modify border or web elements

Server Generated Images

Server & browser independently generate same image Server can customize its own page

Conclusions

• Benefits:– Achieves mutual authentication– Resistant to phishing and spoofing– Relies on human skills

• Weaknesses:– Users must check images

• easier than checking a cert– Local storage of personal image reduces

portability, requires security– Doesn’t address spyware, keyloggers

Status and Future Work

• Iterative design & “lo-fi” testing of interface

• Formal user study

• DSS Mozilla extension

Customized Indicators: Petname Toolbar

Automated Indicators:Secure Random Dynamic Boundaries