SRS Timestamp

[Dale Moore via spf-discuss]

I would post this to the mailing list srs-***@listbox.com, but it
appers that list is deprecated in spite of being listed at
http://www.libsrs2.org/support.html .

Please forgive me if this has been discussed before, but I did some
searching
and didn't find anything appropriate.

In the paper http://www.libsrs2.org/srs/srs.pdf

The resolution is one day, and it is a 10 bit number stored as 2 base32
characters.
The timestamp is computed as unix time / (60 * 60 * 24) mod 2 ^ 10 .

This gives 1024 possible timestamps, with approximately a 3.5 year cycle
before a
timestamp becomes valid again.

And on the wikipedia
http://en.wikipedia.org/wiki/Sender_Rewriting_Scheme


- *The timestamp* (TT) has a one-day resolution in order to make the
address invalid after a few days. Computed as unix
time<http://en.wikipedia.org/wiki/Unix_time>
⁄(60*60*24) mod 210, it can be stored as a two
base32<http://en.wikipedia.org/wiki/Base32> characters,
with a recycling period of about 3.5 years.


So, wouldn't the cycle time be
- 2^10 days or
- 1024 days or
- (1024 / 365) years or
- 2.8 years?

I don't understand where 3.5 years come from.

Dale W Moore



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[Stuart Gathman via spf-discuss]

Post by Dale Moore via spf-discuss
deprecated in spite of being listed at
http://www.libsrs2.org/support.html .
Please forgive me if this has been discussed before, but I did some
searching
and didn't find anything appropriate.
In the paper http://www.libsrs2.org/srs/srs.pdf
The resolution is one day, and it is a 10 bit number stored as 2
base32 characters.
The timestamp is computed as unix time / (60 * 60 * 24) mod 2 ^ 10 .
This gives 1024 possible timestamps, with approximately a 3.5 year
cycle before a
timestamp becomes valid again.
And on the wikipedia
http://en.wikipedia.org/wiki/Sender_Rewriting_Scheme
* *The timestamp* (TT) has a one-day resolution in order to make the
address invalid after a few days. Computed as ^unix time
<http://en.wikipedia.org/wiki/Unix_time> ⁄_(60*60*24) mod 2^10 ,
it can be stored as a two base32
<http://en.wikipedia.org/wiki/Base32> characters, with a recycling
period of about 3.5 years.
So, wouldn't the cycle time be
- 2^10 days or
- 1024 days or
- (1024 / 365) years or
- 2.8 years?
I don't understand where 3.5 years come from.

Originally, the timestamp was 2 base64 characters for 4096 values, for
an 11.2 year cycle. But braindead mailers keep smashing case, and no
amount of preaching, or handing out copies of the email RFCs on street
corners seemed to be able to change that. So the developers switched to
two base 36 chars for the timestamp - for a 3.5 year cycle. A lot of
things were better with a power of 2 modulus, so the final version used
2 base 32 chars for a 2.8 year cycle. But the whitepapers were never
updated.




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