Protecting Applications with Transient Authentication

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Protecting Applications with Transient
Authentication

• Mark D.Corner and Brian D. Noble
• Presenter Jim Cai

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What is authentication?

• Traditional Authentication
• Password (Infrequent, persistent)
• Mobile devices are more fluid
• Usability vs. security
• Transient Authentication
• Token authenticate on users behalf
• Short-range wireless link

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What does TA promise us?

• defend
• Attacks involving physical possession of a device
  (memory, authentication credentials)
• Observation, modification, insertion of messages
• Wormhole attacks
• Does NOT defend
• Malicious, but trusted user
• Buffer overflow
• DOS

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Transient Authentication Principles

• Tie Capabilities to Users
• Only user (not the device) is capable to perform
  sensitive operations
• Decrypting capabilities must be destroyed when
  user leaves

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Transient Authentication Principles

• Do not Harm
• Only Infrequent human tasks (password)
• Acceptable latencies (SSL)
• Secure and Restore on People Time
• encrypt rather than erase

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Transient Authentication Principles

• Ensure Explicit Consent
• User involvement
• Binding (many-to many relationships)
• User authenticate to token periodically (in case
  of token lost)

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Application Transparent Protection

• Advantage
• Protect in-memory process state
• without help from applications
• without user interventions

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Application Transparent Protection

• Implementation
• Process hibernation
• Marked as hibernate
• Wait for interruption opportunity
• Virtual memory encryption
• Throw away decrypted key
• Free memory clearance
• Reverse the process as user returns

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Application Transparent Protection

• Performance issue
• Memory size / processing speed
• Securing application-aware
• Recovering prioritization

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Application Transparent Protection

• Tokens public key must be certified
• Use nonce to identify packet
• Proximity polling msg to notify user absence
  (1sec)

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Application Transparent Protection

• Disadvantages
• Indiscriminate
• Non-sensitive process
• Occasionally sensitive process
• Processes that share memory
• process that depends on constant input or network
  traffic

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Application-Aware Protection

• Provide interfaces for application to identify
  its own secrets
• Identify secrets
• No hard rule (users data, meta-data, network
  data could all be secrets )
• Designers call
• When to encrypt secrets
• When user leaves
• Always encrypt, unless being used
• Choice depends on data size and frequency of use

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Application-Aware Protection

• APIs

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Application-Aware Protection Overview
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Application-Aware Protection Applications

• Pretty Good Privacy
• How does it work?
• Private key (decryption, sign)
• Public key (encryption, verify sign)

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Protect PGP

• Generate a random password P
• P is used to encrypt the private key Kp (PKp)
• The Master key, stored in the token, is used to
  encrypt P (KPGP)
• Process exits when losing authentication
• Display reset

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Modified PGP diagram
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Application-Aware Protection OpenSSH

• Password for authentication, session key for
  encryption
• Decrypted session key remains in memory
• Decrypted password is throw away after
  authentication

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Application-Aware Protection Mozilla
SDR for cookies and password protection, SSL keys
for session encryption Decrypted SSL session key
remains in memory. Cached password and cookies
are decrypted by Secret Decoder Ring every time
it is used SDR password is erased upon user
departure
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Application-aware Limitations

• Sensitive data may no longer be reachable
• in leaked memory
• in memory that has been freed (modify realloc,
  free, delete)
• Application must obscure readable info
• Identifying secrets info

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Evaluations

• Client
• IBM ThinkPad X24,256MB, 1.1GHZ
• Token
• Compaq iPAQ 3870, 64MB
• Bluetooth wireless
• 128 bit encryption

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Evaluations

• Transparent Protection (200MB memory)
• Secure
• 632 ms to freeze processes
• 8.92 s to encrypt 215.9M
• 6.00 ms to zero 2.25M free pages Recovery
• Recovery
• 7.72 s to decrypt
• 21.2 ms to unfreeze process
• Average 10 seconds for secure/recovery

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Evaluations

• PGP

Initial authentication is the only overhead Large
and small files have the same overhead
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Evaluations

• Open SSH

Login accounts for the largest overhead
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Evaluations

• Mozilla

Cookie overhead
Protection and Recovery
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Discussion

• Why does the paper use Mozilla, SSH and PGP to
  conduct the experiment?

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Discussion

• User periodically authenticate the token to
  prevent token lost. How often should this
  authentication be? Does it also cause the tension
  of usability and security?

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Discussion

• Are there further improvements that we can take
  to speed up the securing / recovery process of
  application-transparent approach?