Re: Joins on capabilities that have passed through different membranes

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The name "Ask Bob" comes from a paper by Moni Naor about sharing a secret
without revealing it.  (I have a copy, but it's in a box in my closet.)  In
his paper, Bob told Moni, his manager, about a problem with another
employee.  Later, Carol (I forgot the real name.) told Moni that an
employee had made the same complaint to her.  It would be fine for Moni and
Carol to reveal the identity of the complainer if it was Bob both times but
not otherwise.  Being computer scientists, they came up with 10(?) ways.
For example, Moni would make a flight reservation for Bob, and Carol would
cancel one in the name of the employee who complained to her.  Moni was
explaining these solutions at dinner, when his son asked, "Why didn't you
just ask Bob?"  Moni did, and Bob said it was OK to tell Carol.

I used the son's solution for e-speak, which used path-based names.  You
didn't know if two names received along different paths referred to the
same object.  I didn't think it mattered, but some customers freaked out.
In the Ask Bob protocol you send a different nonce along each path and ask
for it to be returned on the other one.  If you get both nonces back, you
know the references are to the same object.  If you don't, either the
aren't, or the object is lying to you.  To the best of my knowledge, it was
never used.

--------------
Alan Karp

On Mon, Jan 4, 2016 at 7:05 PM, Kenton Varda <[email protected]> wrote:

> I've heard of the "Ask Bob Protocol" mentioned a few times in the context
> of capability equality, but I don't think I've ever heard exactly what it
> does / how it works. Is there a good reference doc? It seems hard to Google.
>
> -Kenton
>

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<div dir=3D"ltr"><br><div class=3D"gmail_extra">The name &quot;Ask Bob&quot=
; comes from a paper by Moni Naor about sharing a secret without revealing =
it. =C2=A0(I have a copy, but it&#39;s in a box in my closet.) =C2=A0In his=
 paper, Bob told Moni, his manager, about a problem with another employee.=
=C2=A0 Later, Carol (I forgot the real name.) told Moni that an employee ha=
d made the same complaint to her.=C2=A0 It would be fine for Moni and Carol=
 to reveal the identity of the complainer if it was Bob both times but not =
otherwise.=C2=A0 Being computer scientists, they came up with 10(?) ways.=
=C2=A0 For example, Moni would make a flight reservation for Bob, and Carol=
 would cancel one in the name of the employee who complained to her.=C2=A0 =
Moni was explaining these solutions at dinner, when his son asked, &quot;Wh=
y didn&#39;t you just ask Bob?&quot; =C2=A0Moni did, and Bob said it was OK=
 to tell Carol.</div><div class=3D"gmail_extra"><br></div><div class=3D"gma=
il_extra">I used the son&#39;s solution for e-speak, which used path-based =
names.=C2=A0 You didn&#39;t know if two names received along different path=
s referred to the same object.=C2=A0 I didn&#39;t think it mattered, but so=
me customers freaked out.=C2=A0 In the Ask Bob protocol you send a differen=
t nonce along each path and ask for it to be returned on the other one.=C2=
=A0 If you get both nonces back, you know the references are to the same ob=
ject.=C2=A0 If you don&#39;t, either the aren&#39;t, or the object is lying=
 to you.=C2=A0 To the best of my knowledge, it was never used.</div><div cl=
ass=3D"gmail_extra"><div><div class=3D"gmail_signature"><br>--------------<=
br>Alan Karp</div></div>
<br><div class=3D"gmail_quote">On Mon, Jan 4, 2016 at 7:05 PM, Kenton Varda=
 <span dir=3D"ltr">&lt;<a href=3D"mailto:[email protected]" target=3D"_bl=
ank">[email protected]</a>&gt;</span> wrote:<br><blockquote class=3D"gmai=
l_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left=
:1ex"><div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote=
">I&#39;ve heard of the &quot;Ask Bob Protocol&quot; mentioned a few times =
in the context of capability equality, but I don&#39;t think I&#39;ve ever =
heard exactly what it does / how it works. Is there a good reference doc? I=
t seems hard to Google.<br></div><div class=3D"gmail_quote"><br></div><div =
class=3D"gmail_quote">-Kenton</div></div></div></blockquote></div></div></d=
iv>

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