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I'm trying to code the following from RFC 7906 using pyasn1:

    aa-keyAlgorithm ATTRIBUTE ::= {
       TYPE KeyAlgorithm
       IDENTIFIED BY id-kma-keyAlgorithm }


    KeyAlgorithm ::= SEQUENCE {
       keyAlg            OBJECT IDENTIFIER,
       checkWordAlg  [1] OBJECT IDENTIFIER OPTIONAL,
       crcAlg        [2] OBJECT IDENTIFIER OPTIONAL }

The relevant section of code I have presently is:

id_kma_keyAlgorithm = ObjectIdentifier('2.16.840.1.101.2.1.13.1')
aes256_gcm_oid = ObjectIdentifier('2.16.840.1.101.2.1.13.1')
id_keyAlg_ckword64 = ObjectIdentifier('1.2.826.0.1145.0.5.0')
id_keyalg_crc32 = ObjectIdentifier('1.2.826.0.1145.0.5.1')

class aa_keyAlgorithm(Sequence):
    componentType = NamedTypes(
         NamedType('attrType', ObjectIdentifer()),
         NamedType('attrValues', KeyAlgorithm())
    )
class KeyAlgorithm(Sequence):
    componentType = NamedTypes(
          NamedType('keyAlg', ObjectIdentifier()),
          OptionalNamedType('checkWordAlg', ObjectIdentifier().subtype(
               implicitTag=Tag(tagClassContext, tagFormatSimple, 1))),
          OptionalNamedType('crcAlg', ObjectIdentifier().subtype(
               implicitTag=Tag(tagClassContext, tagFormatSimple, 2)))

key_algorithm = aa_keyAlgorithm()
key_alg_attrs = KeyAlgorithm()

key_algorithm.setComponentByName('attrType', id_kma_keyAlgorithm)
key_algorithm.setComponentByName('attrValues', key_alg_attrs)

key_alg_attrs.setComponentByName('keyAlg', aes256_gcm_oid)
key_alg_attrs.setComponentByName('checkWordAlg',id_keyAlg_ckword64, matchTags = True)
key_alg_attrs.setComponentByName('crcAlg', id_keyalg_crc32, matchTags = True)

I am getting the following error:

Component-value is tag-incompatible: <ObjectIdentifier value object, tagSet <Tagset object, tags 0:0:6>, payload [1.2.826.0.1145.0.5.0]> vs <NamedTypes object, types <NamedType object, type KeyAlgorithm=<ObjectIdentifier schema object, tagSet <TagSet object, tags 0:0:6>>>, <OptionalNamedType object, type checkWordAlg=<ObjectIdentifier schema object, tagSet <TagSet object, tags 128:0:1>>>, <OptionalNamedType object, type crcAlg=<ObjectIdentifier schema object, tagSet <TagSet object, tags 128:0:2>>>>

The code runs fine without trying to add the context tags. I've tried various combinations of matchTags = True/False throughout the code. What is I need to change to make the tags compatible?

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  • I've made some progress on this. I also included the tagset within my original declaration of the ObjectIdentifier. This got rid of the error and included the context tags but has caused a new issue of the component itself is now missing. New question on this link stackoverflow.com/questions/79588695/… Commented Apr 23 at 13:09
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