CRMF EncryptedValue

[Ari Kermaier <arik@xxxxxxxxx>]

It seems to me that the EncryptedValue structure defined in CRMF (used in 
POPOPrivKey and PKIArchiveOptions) may be incompletely specified.

The syntax from draft-ietf-pkix-rfc2511bis-00 Section 6.4 is:

EncryptedValue ::= SEQUENCE {
      intendedAlg   [0] AlgorithmIdentifier  OPTIONAL,
      -- the intended algorithm for which the value will be used
      symmAlg       [1] AlgorithmIdentifier  OPTIONAL,
      -- the symmetric algorithm used to encrypt the value
      encSymmKey    [2] BIT STRING           OPTIONAL,
      -- the (encrypted) symmetric key used to encrypt the value
      keyAlg        [3] AlgorithmIdentifier  OPTIONAL,
      -- algorithm used to encrypt the symmetric key
      valueHint     [4] OCTET STRING         OPTIONAL,
      -- a brief description or identifier of the encValue content
      -- (may be meaningful only to the sending entity, and used only
      -- if EncryptedValue might be re-examined by the sending entity
      -- in the future)
        encValue       BIT STRING }

How does the recipient of such a structure know what block padding scheme 
may (or may not) have been used with the symmetric encryption algorithm? 
CMS, for example, specifies mechanisms whereby this information is conveyed 
with similar message structures, but I can't seem to find any mention of 
this in CMP/CRMF. Any ideas, anyone?

Ari