Security Solutions for RESCUE

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Security Solutions for RESCUE

• Jason E. Holt isrl_at_lunkwill.org
• Brigham Young University
• Internet Security Research Lab
• isrl.cs.byu.edu

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Logcrypt forward security

• Forward security If a resource is secure at time
  t, it will remain secure at all tt.
  
• Example ephemeral modes in TLS

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Logcrypt preliminaries

• Cryptographic hash function
• Arbitrary size inputs, constant size output
  (usually 128-512 bits)
  
• Preimage resistant
• Collision resistant
• Hash chain s1h(s), s2h(s1), s3h(s2)

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Logcrypt forward security

• Securely record the initial public or secret
  value
  
• Derive new secrets from the initial secret
• Use a secret to MAC/encrypt each piece of
  incoming data
  
• Delete secrets immediately after use
• Verifiers later check data against initial value

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Symmetric MAC/encrypt with Logcrypt
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Symmetric MAC/encrypt with Logcrypt
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Public verification with Logcrypt
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Public verification from IBE

• Identity Based Encryption
• Private Key Generator (PKG) has a public/private
  value
  
• PKG issues private keys corresponding to strings
  like isrl_at_lunkwill.org to users
  
• Anyone can generate the public key for any string
  given only the PKG public value
  
• Avoids chicken-and-egg problems, key distribution
  issues

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Maintaining multiple concurrent logs
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Logcrypt limitations

• Truncation
• Metronome entries
• Compromise of future entries
• Fabrication of an entire log

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Logcrypt applications

• Anything requiring tamper-evidence
• Emergency requisition logs
• Accountability for public officials after a
  disaster
  
• Discourages abuse and helps prevent cover-ups
• Corporate bookkeeping

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Logcrypt applications

• Evidence-gathering devices
• Voice recorders
• Still cameras
• Video cameras
• Uses
• Journalism
• Police forensics
• Intelligence gathering in hostile territory
• Police/military gun-cam
• Surveillance cameras

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Logcrypt applications

• System logs
• Like Tripwire for system logs
• Could automatically email initial secret to
  external system at install time
  
• Logs can be verified on an external secure
  machine, or by rebooting to a known secure OS

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Hidden Credentials

• Traditional trust negotiation
• Resource request / policy disclosure / credential
  disclosure / resource delivery
  
• Hidden credentials
• Public-key encryption function which takes a
  policy instead of a public key
  
• E(M, Alice Secret clearance OR Alice TOP
  Secret clearance)

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Hidden Credentials

• Reduces network traffic
• Instead of 2 full round trips (request/policy/cred
  ential/delivery), a single message suffices
  
• Applications
• Policy enforcement in courier networks
• Delivery of resources before a disaster

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Hidden Credentials

• Solves the going-first problem
• Usually, one party must show the first
  credential
  
• IPSec allows either party to go first
• Hidden credentials avoid showing credentials
  entirely
  
• Applications
• Prevents network scanning and credential
  harvesting

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Hidden Credentials

• Resolves policy cycles
• Conceals policies from unqualified users
• Credentials need never be shown

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Other Work

• Content-triggered trust negotiation
• Policies created on-the-fly by classifying data
  (eg., documents with agent names are always top
  secret)
  
• Phishing Warden
• Surrogate trust negotiation
• Mobile devices refer others to a secure central
  repository
  
• Central repository could change policies without
  contacting device
  
• THOR The Hybrid Online Repository

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Thoughts on Privacy

• Identification is useful between peers
• Pseudonymous and reputation systems
• Identification and surveillance are dangerous
  when applied to subordinates
  
• 1984, McCarthyism
• Psychological tendency to act in expected ways
• Creates a fear and accusation culture
• Thwarts risk-taking
• Cambodian holocaust

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Thoughts on Privacy

• Free governments work by subverting the
  traditional top-down government
  
• Ability to hold government responsible is
  critical
  
• Transparency is thus an absolute requirement for
  government processes
  
• Intra-government behavior (senate ethics)
• Applications of power (due process, Geneva
  Convention)

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Thoughts on Privacy

• Security systems should focus privacy downward,
  and accounting integrity upward
  
• Privacy is not the opposite of security
• Technologies should focus on detecting bad
  behaviors, not identifying potential criminals