OSPF WG

Cryptographic Algorithm Implementation Requirements for

OSPF draft-bhatia-manral-crypto-req-ospf-00.txt

Vishwas Manral, IPInfusion

Manav Bhatia, Lucent TechnologiesIETF 67, San Diego, USA

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)

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.

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.

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.

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

(1) NULL auth cannot be used if operator requires network security.

(2) Used mostly to avoid accidental introduction of router in a domain. Not useful if security is required

Authentication Algo SelectionOld 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

Questions?