Hi !
My name is Piotr and I am completely new here.
I would like to say hello to all members of this
forum.
I have just started to work with ASN.1,
so this is my first attempt to use power
of "The ASN.1 Mailing List" :)
Please forgive me if my question is too easy for
someone.
I'm trying to understand some tagging rules in ASN.1
Could you please someone help me in understanding
this tagging issues better ?
During my investigation - among other things - I found
that :
"IMPLICIT TAGGING: this is where the new tag over-
rides the old tag and type information which was
carried by the old tag"
I found an example too :
Person ::= SEQUENCE {
title [0] IMPLICIT IA5String OPTIONAL,
name IA5String }
form1 is :
form1 Person ::= {
title "Sir",
name "Peter",
}
I agree that it should be coded in the following
way :
0x30 0x0c
(***) 0x80 0x03 0x053 0x69 0x72
0x16 0x05 0x50 0x65 0x74 0x65 0x72
But I don't understand how decoder should now
what ANS.1 type is mentioned in (***) ?
It is not possible to guess IA5String tag type
from 0x80 0x03 0x053 0x69 0x72 binaries ....
0x80 ---> class: context-specific
method: primitive
tag type number: 0 (???)
Could you please someone explain it to me, how decoder
can recognize appropriate tag type ?
I will appreciate any kind of help !
I was reading a lot of materials : official and
less official about this tagging issues, but I
haven't met any clear explanation on my qestion ....
Thanks in advance for your help !
Best regards,
Piotr
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