[ASN1] BER encoding of OID

[Banibrata Dutta]

Hi,

 

I was wondering if someone could help me understand the BER encoding for an OID type value.

I read the section 8.19 of  X.690, (also cut-n-paste here), but couldn't really figure out how to came up the binary representation of the example being explained.

 

8.19.5 The numerical value of the ith sub-identifier, (2 <= i <= N) is that of the (i + 1)th object identifier component.

EXAMPLE

An OBJECT IDENTIFIER value of:

{joint-iso-itu-t 100 3}

which is the same as:

{2 100 3}

has a first sub-identifier of 180 and a second sub-identifier of 3. The resulting encoding is:

OBJECT

IDENTIFIER Length Contents

06₁₆ 03₁₆ 813403₁₆

 

As explained in the sections 8.19.1-8.19.4, the way I compute the representation is...

2x40 + 100 = 180 (sub-identifier-1)

3 (sub-identifier-2).

 

How do these 2 sub-identifiers make up  (813403₁₆), is not at all clear from the prior sections.

 

thanks & regards,

Bani

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