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asn.1der

Can ASN.1 *STRING field have zero length?

Does ASN.1 standard allow UTF8String or PrintableString to have zero length? I've been looking for this information in ASN.1 specs but can't seem to find it. I'm using DER encoding.

Solution

  • Yes

    Consider following specification

    Example DEFINITIONS AUTOMATIC TAGS ::= 
BEGIN
  Name ::= PrintableString                       
END

    and following value

    value Name::= ""

    BER (and DER) encoding is 

    > ASN1STEP: Encoding of value notation  for PDU #1:
> 
> Encoding to the file 'data.ber' using BER encoding rule... Name
> PrintableString: tag = [UNIVERSAL 19] primitive; length = 0   ""
> Encoded successfully in 2 bytes: 1300

    Tested on https://asn1.io/asn1playground/