Is there a algo or way to search a particular tag / tag value in ASN
byte stream ?
If you are using (BER, CER, or DER, yes, it's easy enough. If you are
using PER, no, it's not possible since tags are not encoded. I'll assume
you're working with BER.
You'll need to examine the initial octet, which is always a tag, and
making use of the constructed-bit within the tag and the length following
the tag, you should be able to find the following tag, etc.
Please consider reviewing one (or both) of the ASN.1 reference texts which
OSS makes available for free download. You will find them at
http://www.oss.com/asn1/booksintro.html
Neither will explicitly outline an algorithm, but if you understand how
tags and lengths are encoded, you can figure one out for yourself. One
warning: a cursory examination of a trivial set of tags and lengths might
convince you that these fields are only one byte long. The truth is that
they can be many bytes long and you need to know when and how. A little
study in the texts will go a long way.
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