Re: Character set for GPG keys

[David W. Hodgins]

On Fri, 29 Mar 2013 15:28:39 -0400, Anonymous <anon...@hoi-polloi.org> wrote:

> What is the full acceptable character set for GPG pass phrases? I'm
> looking to find the answer both for public key and symmetric pass
> phrases.
> While I'm at it, what is the maximum size for a gpg pass phrase?
> I've seen conflicting claims on this. Thanks for any help.

I don't see any limits imposed by gpg itself. The pw is a c char
string, so posix limits apply to that.

I think, it's 2048 bytes (_POSIX2_LINE_MAX)
https://www.cs.utah.edu/dept/old/texinfo/glibc-manual-0.02/library_27.html

It's expecting utf-8 characters, so should accept anything except a null
character, which terminates the string.

Regards, Dave Hodgins

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[Fritz Wuehler]

In article <op.wup8bve...@hodgins.homeip.net>

"David W. Hodgins" <dwho...@nomail.afraid.org> wrote:
>
> On Fri, 29 Mar 2013 15:28:39 -0400, Anonymous <anon...@hoi-polloi.org> wrote:
>
> > What is the full acceptable character set for GPG pass phrases? I'm
> > looking to find the answer both for public key and symmetric pass
> > phrases.
> > While I'm at it, what is the maximum size for a gpg pass phrase?
> > I've seen conflicting claims on this. Thanks for any help.
>
> I don't see any limits imposed by gpg itself. The pw is a c char
> string, so posix limits apply to that.
>
> I think, it's 2048 bytes (_POSIX2_LINE_MAX)
> https://www.cs.utah.edu/dept/old/texinfo/glibc-manual-0.02/library_27.html

Okay, thanks, Dave. A 2KB passphrase should be pretty good.

>From looking around I see that the part of the POSIX character set
that can be used to enter a key appears to be this:

!"#$%&'()*+,--./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^^__`abcdefghijklmnopqrstuvwxyz{{|}}~

But there are various duplicate characters in there, at least on my
system; e.g. the "backslash" \ and "reverse-solidus" \ characters
appear to be the same ASCII code and this is the case with some
other characters.

So stripping out the duplicates I ended up with this character set:

!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~

which is indentical, I think, to Base95.

So I'm thinking that Base95 is my character set for the GPG pass
phrase.

> It's expecting utf-8 characters, so should accept anything except a null
> character, which terminates the string.

I'm familiar with using utf-8 codes to render various glyphs in
HTML, but I think that what you're telling me is that since the
POSIX and/or Base95 character sets are a subset of utf-8 that it's
acceptable.

That doesn't mean that I could somehow enter the character
represented by, say, x270D and have it be a part of the passphrase,
right? I could enter the utf-8 code for it, I suppose and be
content with that, I guess.

Thanks again for your help on this.