Re: [apps-discuss] draft-farrell-decade-ni-02: glitch in examples

[Stephen Farrell <[e-mail]>]

Hi again James,

On 04/10/2012 05:08 AM, Manger, James H wrote:
> Stephen,
>
> A couple of "typos" in draft-farrell-decade-ni-02:
>
> The example SubjectPublicKeyInfo is shown in a strange way: each pair of bytes is shown in the opposite order to bytes on the wire (and the offset at the start of the line is in nibbles). The first few bytes of the BER-encoding are 30 820122, while the example starts:
>     0000000 8230 2201 0d30 0906 862a 8648 0df7 0101
>
> The BER-encoding is actually:
>     30 820122
>        30 0D
>           06 09 2A86
>        ...
>
> Half of the example names are wrong, almost certainly due to this strange format.

Yep. That was me being sloppy ("od -x" did used to do the right thing
on some platform I used sometime in the distant past I think;-)

>
> The 120-bit "Binary Name" in figure 6 is wrong. It swaps the order of bytes (after the first). It should be:
>    03 53269057 E12FE2B7 4BA07C89 2560A2

Ditto.

>
> The human-readable names (120-bit and 32-bit) are wrong. They have base32-encoded pairs of bytes in the wrong order. They should be:
>    sha-256-120;kmtjav7bf7rlos5apseskyfc;????
>    sha-256-32;kmtjavy;????

We're deleting the last character, yes. Might need to think more
about I18N for that all right. I'm told dropping the last character
is ok, but have yet to check.

>
> I am not sure what the correct checksums are.
>
> The example checksums (eokv and csdh) look wrong. I assume the 4 base32 chars in the checksum should encode 5+5+5+1 bits respectively of the 16-bit CRC. Hence the last char encodes 1 bit, padded with 4 zeros: either 00000 or 10000, which should give 'a' or 'q' (not 'v' or 'h').
>
> P.S. A CRC16 is calculated over an array of bytes. However the input is defined as a text string. I guess ASCII/UTF-8 encoding is assumed. It might be better to calculate the CRC over the bytes of the truncated hash.

Fair point. OTOH, that'd mean omitting the "nih:sha-256;" part but
I guess that'd be not much harm.

I suspect that you may be right about the checksum. Will check with
co-authors more involved with CoAP (Ari basically) to see what they
prefer, since its them that want the CRC.

I've posted a -03 that I hope is good now, other than the CRC input.

Thanks again,
Stephen.


>
> --
> James Manger
>
>