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Rich Salz wrote:
>> A BER decoder is also a DER decoder - DER is just a profile of BER
>> with all the encoder's options removed!
> Exactly, which is why I said DER is a canonicalization of BER, and
> what's necessary for hashing to work. If there are fewer options than
> surely there must be less code in a DER reader.
Hmmm, only in one case I can think of.
The restrictions on BER for DER are things like:
1) Things that can be in any order in BER must be in a specific order in DER
2) Unused bits that can contain anything in BER must be all zero in DER
...those two make NO DIFFERENCE in the decoder, of course, and:
3) In BER there are two forms of variable-length structure; one with a
length written at the beginning, and one that instead uses a sentinel
value to mark the end. DER only lets you use one of the options. So the
decoder would have one less thing to worry about there.
But that's the only difference to the decoder I can think of! The
difference to the encoder is far more noticeable :-)