Introduction%20to%20Cryptographic%20Key%20Management

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Introduction to Cryptographic Key Management
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Outline

• Context
• Definitions
• Description
• Principles
• Illustrations and Demonstrations
• Recommendations

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Context -- Cryptography is

• use of secret codes to hide and authenticate data
• suited to open and hostile environments
• broadly applicable
• portable
• composable
• can emulate any media or environment control
• arbitrarily strong
• effective
• efficient

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Context

• cost of crypto is low
• falling with the cost of computing
• relative strength is rising
• strong as we need it to be
• stronger than other security mechanisms
• strong link in the security chain
• robust, resilient, not likely to break
• very unlikely to collapse
• advantage is to the cryptographer

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Modern Cryptography - the great inventions

• automatic encoding and decoding
• the large independent key variable
• complexity-based encryption (DES)
• asymmetric key
• automatic key management

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Symmetric Key Cryptography
Out-of -channel exchange
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Key Management

• generation
• recording
• transcription
• distribution
• installation
• storage
• change
• disposition
• and control

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Key Management

• generation
• recording
• transcription
• distribution
• installation
• storage
• change
• disposition
• and control

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Key Management

• is very important
• must be rigorous and disciplined
• principal point of attack
• not intuitive
• easy to screw up

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Modern Key Management

• fully automated, (i.e., no manual operations)
• permits frequent key change (e.g., file, session,
  message, transaction, or other data object)
• increases the effective key length or security
• balances the interests in the key of multiple
  parties
• application of RSA
• and smart cards
• may be integrated or stand-alone

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Applications of Key Management

• increase effective strength
• compensate for limitations of algorithm
• involve multiple people in sensitive duties
• personal security environments

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Principles of Key Management

• No key may ever appear in the clear
• All keys must be randomly generated by a crypto
  engine
• Keys must be chosen evenly from the entire key
  space
• Must not have any (visible) structure
• Key-encrypting keys are separate from data keys
• Everything encrypted under a key-encrypting key
  must originate within a crypto engine
• Key management must be automated

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Asymmetric Key Cryptography

• key has two parts
• what is encrypted with one part may only be
  decrypted with the other
• only one part need be kept secret
• requires a minimum of prearrangement

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Public Key Issues

• public key need not be kept secret
• must be the right key
• i.e., association between public key and legal
  person
• encapsulated in a certificate
• signed by someone who knows

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Digital Envelope
BobsPrivate Key
BobsPublic Key
Bob
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Digital Signature
JohnsPrivate Key
JohnsPublic Key
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Characteristic DES
RSA Relative
Speed Fast
Slow Functions Used
Transposition Multiplication
Substitution
Key - length
56 bits 400-800
bits Least Cost Attack
Exhaustion Factoring
Cost of Attack
Centuries Centuries
Time to Generate Micro-seconds
Tens of Seconds a Key
Key Type Symmetric
Asymmetric
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Hybrid Cryptography
JanesPublic Key
JanesPrivate Key
Jane
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Key Management Systems and Protocols

• PGP
• RSA Secure
• Kerberos KDC
• Secure Socket Layer (SSL)
• XML Key Management System
• X509 Certificates/PKIX
• BBN SafeKeyper
• ISAKMP and Oakley

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PGP

• software
• used to encrypt files or messages
• under a block cipher (IDEA)
• generates the block cipher key
• uses RSA to exchange the block cipher key
• uses the block cipher to hide the private key
• uses an endorsement system to exchange public
  keys
• uses a passphrase to generate the key-hiding key
• If the passphrase is forgotten, files cannot be
  recovered

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ViaCrypt PGP, Business Edition

• uses two levels of key-hiding key
• the one used to protect the private key is itself
  encrypted twice.
• once under the users pass-phrase
• once under a system of keys
• such that a specified number of parties must act
  in concert to recover the key.

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• add-in to file manager
• encrypts files or directories
• on command
• or by default
• automatically
• prompts user for passphrase when needed
• support multi-party emergency management over-ride

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Kerberos Key DistributionCenter

• Kerberos KDC is a trusted server
• that shares a secret with every entity in a
  domain.
• When two processes, A and B, want to talk,
• Kerberos generates a key
• and encrypts it twice, once under the secret
  shared with each, and publishes it.
• Each process uses its own secret to decrypt the
  key so that they can talk to each other.

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KDC
Simplified Kerberos Schematic
Im fred. I want a ticket for payroll
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3
Client (fred)
1, 4, 8
Server(payroll)
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Secure Socket Layer (SSL)

• API and protocol for clients to talk to servers

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BBN SafeKeyper

• book-size hardware box with unique identity
• generates a private key/public key pair
• private key cannot ever be removed from the box
• box has three physical keys
• beneficial use of the key requires the box and
  the physical keys
• box contains a public key belonging to BBN
• publishes its own identity and public key under
  the BBN public key
• so that BBN can recognize it and certify it.

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BBN SafeKeyper Backup

• SafeKeyper can publish multiple parts of the
  private key
• encrypted in such a way
• that with a specied number of the parts
• another SafeKeyper box can reconstruct the
  private key.

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BBN SafeKeyper Applications

• Certificate management support for Internet
  Privacy Enhanced Mail
• Exchange of work orders, purchase orders,
  letters of credit, bids, proposals, or other
  official documents
• Software license distribution and usage control
• Electronic funds transfer
• Network and host sign-on authorization
• Detection of tampering with, or forgery of,
  computer-based applications
• Any place high integrity key storage is indicated

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Encryption in the Internet
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Encryption in the Internet
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