Interesting. A new RR type must be used. Are the issues related to
a new RR type resolved?
Rather than dropping characters in the local-part section, this might
impose a security problem when a character repertoire in the local-
part is unknown. DNS permits case-folding. Even without case
folding, the DNS code space represents about 25% of the possible code
points. It would be safer using base32 encoding. This encoding
could provide a means to concatenate up to a maximal domain name size
and still provide about 100 byte answers. With base32, 63 bytes can
encode 315 bits which represent 39 bytes and 3 bits. This would
represent a 62% increase in the label size needed. The padding for
the base32 could not be "=" as defined in rfc3548, but instead could
be "8" for padding. Use of "_user" reduces available name space by 6
bytes. The draft did not indicate whether truncation removed the
left-most or right-most portion of the local-part. Consider the
answer carefully. How is truncation assured to occur at the same
limit uniformly among the verifiers?
-Doug
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