Re: [Anima-bootstrap] voucher yang

Michael Richardson <mcr+ietf@sandelman.ca> Fri, 03 March 2017 14:12 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Kent Watsen <kwatsen@juniper.net>
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Date: Fri, 03 Mar 2017 09:12:33 -0500
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Subject: Re: [Anima-bootstrap] voucher yang
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Kent Watsen <kwatsen@juniper.net> wrote:
    >> What I'm saying is that the pledge can't know how the owner was verified.
    >> The pledge actually has to process the same as for "verified" as for
    >> "logged".  It doesn't change the pledge's behaviour.

    > But it does.  Some pledges may be coded to only support 'verified'
    > vouchers.

I agree, but the verification involved can't be confirmed by the pledge.

    > The DER itself works for me (the privacy concern seems minor).  It's
    > also more code (relative to just using an openssl command line option),
    > but actually it's
    > one step less code than calculating the SHA256 fingerprint.

A constrained device might not have a shell to run an openssl command line :-)

    >>> I'm okay with PCRE in theory, but I've read that a compiled stripped
    >>> library is large, do you know?
    >>
    >> I don't know. I don't want either :-)
    >> If I have to pick a regex library (vs shell-style globbing...) then
    >> I'd rather pick PCRE if we can find a stable reference.

    > As discussed in another thread, I'm beginning to think that we should
    > do away with having a single voucher for many devices, because we'd
    > want revocations to be as granular as possible.

Good!

    >>> A 'binary' type would allow the nonce to be any length octet sequence,
    >>> which is converted to base64 encoded string for JSON.  Is this what
    >>> you want?
    >>
    >> I want as much entropy in as small a space as possible.
    >> string seems to waste 2-bits per byte if it's base64 encoded in a binary
    >> format (CBOR).  If JSON has to base64 encode things, I'm okay with that.
    >>
    >> I would assume that integers get network-byte order considerations which
    >> might lead to implementation bugs, where as binary[8] (if such a thing
    >> exists) would not.  I think uint64 might be too small.

    > Okay, let's change the nonce to a binary type.

Can we say the nonce is 8 to 32 bytes in size?
If we have to pick a single number, I'd say 16 bytes.

--
Michael Richardson <mcr+IETF@sandelman.ca>ca>, Sandelman Software Works
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