Encoding in case you are using BER rule is TLV format i.e. Tag Length Value
format and each member of the sequence (KRN-SAFE-BODY) is assigned a unique
Tag. This Tag value helps in recognizing which member is it.
----- Original Message -----
From: "Gustavo V. G. C. Rios" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, October 29, 2003 6:58 AM
Subject: [ASN.1] (I AM DESPERATE, PLEASE) Beginner Question: ASN1 & Kerberos
(rfc1510.txt)
> Dear gentleman,
>
> i am beginning studying ASN as an requirement for understanding kerberV
> security protocol. One of its message specification is the following:
>
> KRB-SAFE-BODY ::= [APPLICATION 20] SEQUENCE {
> user-data[0] OCTET STRING,
> timestamp[1] KerberosTime OPTIONAL,
> usec[2] INTEGER OPTIONAL,
> seq-number[3] INTEGER OPTIONAL,
> s-address[4] HostAddress,
> r-address[5] HostAddress OPTIONAL
> }
>
> My doubt regards with the decoding of the input stream. For the usec and
> seq-number values i have three possible scenarios:
>
> 0) The two values are present,
> 1) None of them are present,
> 2) Just one of them is present.
>
> Since both are optional and have the same type, for scenario 2, how will
> i *correctly* decode an input stream? I.e. , the next value to be decode
> is an integer, but will i see it as the usec or the seq-number value?
