Simple Authentication schemes for ALC and NORM draft-ietf-rmt-simple-auth-for-alc-norm-00

1
Simple Authentication schemes for ALC and
NORMdraft-ietf-rmt-simple-auth-for-alc-norm-00

• IETF 73 Minneapolis, November 2008
• Vincent Roca (INRIA)

2
General

• now a WG Item document
• as decided during IETF71
• summary of the proposal
• this I-D and TESLA I-D introduce several
  packet-level sender authentication/integrity
  check schemes for ALC and NORM
• all of them define specific EXT_AUTH header
  extensions, one per authentication scheme

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General (cont)

• these HE start by the same ASID (Auth Scheme ID)
  4-bit field
• goal is to enable a mixed use of these schemes in
  the same session, even on the same communication
  path
• e.g., TESLA for downstream NORM traffic, and
  Group MAC for the upstream traffic
• the ASID/auth. scheme mapping is communicated
  out-of-band, as part of the session description
• there is no fixed IANA value

0 1 2
3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7
8 9 0 1 2 3 4 5 6 7 8 9 0 1 -----------
---------------------
HET (1) HEL ASID (scheme
specific) ------------------
--------------
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Record of the changes

• RSA digital signatures
• added text detailing how to use RSA signatures
• as in TESLA I-D
• we also mention SHA-256 (rather than SHA-1)
• corrected a mistake
• the parameters to be communicated to the
  receivers must include the signature crypto
  function (e.g., SHA-256)

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Record of the changes (cont)

• ECC (elliptic curve crypto) digital signatures
• added discussion in introduction
• higher performances than RSA-based signatures
  (see RMT Security discussion I-D)
• but patent claims exist
• we mention ECC but do not define any scheme for
  them
• QUESTION should we detail the use of ECC or
  leave it open for a future (tiny) document?

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Record of the changes (cont)

• Group MAC
• clarified that SHA-256 is recommended
• clarified that during HMAC-SHA output
  truncation, we need to keep the MSB

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Record of the changes (cont)

• Combined use of Group MAC/Digital Signatures
• BEFORE use two separate EXT_AUTH HE
• NOW a specific EXT_AUTH HE, that gathers the
  signature the Group MAC fields
• motivated by
• a lower overhead (32 bits smaller)
• a clear specification that Group MAC encompasses
  the digital signature field (calculated first)
• Security section added
• adapted from that of TESLA I-D

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Next steps

• probably a new version
• especially if ECC is included
• and then WGLC