As for quoted-printable, I guess I'm just skeptical that a checksum is
necessary. If it isn't textual data, you probably won't use q-p. If it
is textual data, a checksum is highly problematic across, e.g.,
ascii-ebcdic gateways. So I just don't see it as being worth the effort.
I'm unclear as to why a checksum is so problematic across ASCII-EBCDIC
gateways. You just have to know that the checksum is to be computed
using ASCII, not EBCDIC, codes. This is what Kermit implementations on
IBM mainframes do all the time. Works fine.
It is important that the ASCII-EBCDIC translate tables be correct.
With something like BASE64, where the character set is restricted to
the invariant subset, it is not a problem. I don't recall offhand if
quoted-printable restricts itself to the invariant subset. If not,
that could be a problem when more than one EBCDIC host is involved. In
such a case a checksum would tell you when something did not translate
properly. This could be important for some kinds of text, such as
source code.