OSPF%20WG

1
OSPF WG

• Cryptographic Algorithm Implementation
  Requirements for OSPF
• draft-bhatia-manral-crypto-req-ospf-00.txt
• Vishwas Manral, IPInfusion
• Manav Bhatia, Lucent Technologies
• IETF 67, San Diego, USA

2
Different OSPF Auth Schemes

• NULL, Simple and Cryptographic
• Recent Reports of attacks on collision resistance
  properties of MD5 and SHA-1
• Cryptographically stronger algorithms have been
  proposed in the WG (HMAC-SHA-1, etc)

3
New Algorithms keep coming ..

• In Cryptography new algorithms surface
  continuously and existing one are continuously
  attacked ..
• Thus the choice of mandatory-to-implement
  algorithms should be conservative to minimize the
  likelihood of OSPF being compromised.
• Would not want to change the OSPF spec each time
  a cryptographically stronger algorithm is
  suggested.
• Eg., DES in the older IPsec RFC was a MUST but
  now has become a SHOULD NOT. Same goes with MD5
  in the IPsec space.

4
Interoperability Issues

• There should be a document that tells which
  algorithms to support and which not for minimum
  interoperability.
• With time the number of algorithms to support
  will increase and we need a minimum set of
  algorithms as well as their current state of
  support documented
• The document would specify the MUST/ MAY/ SHOULD/
  SHOULD NOT for algorithms that are to be
  supported
• This would be a running document that can be
  changed as and when newer algorithms come and the
  older ones get deprecated
• For IPsec the algorithms supported in RFC2401 and
  the ones in RFC4305 have changed. In fact some
  MUST have become SHOULD NOT etc.

5
Additional RFC 2119 terms

• SHOULD Same as SHOULD. However, it is likely
  that an algorithm marked as SHOULD will be
  promoted at some future time to be a MUST.
• MUST- Same as MUST for now. However, its expected
  that at some point in future this algorithm will
  no longer be a MUST
• MAY - Same as MAY for now. However, its expected
  that this algorithm may get promoted at some
  future time to be a SHOULD.

6
Auth Scheme Selection when Security is required

• Old RFC New
• Req Requirement
  Authentication Scheme
• ------ -------- ------------------
  --------------------------------
• MUST 2328 SHOULD NOT Null
  Authentication (1)
• MUST 2328 SHOULD NOT Simple
  Password (2)
• MUST 2328 MUST
  Cryptographic Auth
• NULL auth cannot be used if operator requires
  network security.
• Used mostly to avoid accidental introduction of
  router in a domain. Not useful if security is
  required

7
Authentication Algo Selection
Old Old New Req RFC
Requirement Authentication
Algorithm ------ --------
------------------ -------------------------
------- MUST 2328 MUST-
Keyed MD5 - -
SHOULD HMAC-SHA-1 -
- MAY
HMAC-SHA-256/
HMAC-SHA-384/

HMAC-SHA-512 Bhatia, M., Manral, V., White,
R. and Barnes, M.," OSPF HMAC Cryptographic
Authentication, Work in Progress
8
Questions?