Base64 encoding applied to different unicode texts always yields different base64 texts ... true or false?

Philippe Verdy via Unicode unicode at
Sun Oct 14 16:59:05 CDT 2018

Le dim. 14 oct. 2018 à 21:21, Doug Ewell via Unicode <unicode at>
a écrit :

> Steffen Nurpmeso wrote:
> > Base64 is defined in RFC 2045 (Multipurpose Internet Mail Extensions
> > (MIME) Part One: Format of Internet Message Bodies).
> Base64 is defined in RFC 4648, "The Base16, Base32, and Base64 Data
> Encodings." RFC 2045 defines a particular implementation of base64,
> specific to transporting Internet mail in a 7-bit environment.

Wrong, this is "specific" to transporting Internet mail in any 7 bit or 8
bit environment (today almost all mail agents are operating in 8 bit), and
then it is referenced directly by HTTP (and its HTTPS variant).

So this is no so "specific". MIME is extremely popular, RFC 4648 is
extremely exotic (and RFC 4648 is wrong when saying that IMAP is very
specific as it is now a very popular protocol, widely used as well). MIME
is so frequently used, that almost all people refer to it when they look
for Base64, or do not explicitly state that another definition (found in an
exotic RFC) is explicitly used.
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