[hashcash] Re: hashcash v1 questions

  • From: Justin <justin-hashcash@xxxxxxxx>
  • To: hashcash@xxxxxxxxxxxxx
  • Date: Tue, 1 Jun 2004 18:01:14 +0000

On 2004-06-01T05:28:37-0400, Adam Back wrote:
> > Putting extra stuff into the header makes line-length an issue, 
> I think we are already close to having a line-length issue, especially
> if we include sub-puzzles.  Practically you want sub-80-chars.

Isn't an 80 character limit unnecessary?  I looked through my mailbox, and
Exchange has a 40-byte hex field at the beginning of its message-id, which
tends to make its message ids extremely long (given the penchant of
Windows admins to name machines

I have a handful of messages with 90+ character Exchange-generated MID
headers that aren't line-wrapped.

> > X:0405310625:hashcash@xxxxxxxxxxxxx:25:sender@xxxxxxxxxxxxxx:asdlkfj1325ASDFJ

I don't like the idea I suggested of including the sender's address, and
you're right, a good base64 random field is just as good as a timestamp.
Implementations could even use the 16.4 bits of HHMMSS information and put
that in the high 18 bits of the random field, saving 3 bytes of stamp

Is the length of the random field fixed in v1?  In v0 it was fixed at 96
bits, right?

> > I understand the rationale behind multiple puzzles, but people sending
> > generating stamps should allow that it might take up to an order of
> > magnitude longer than normal.  If I expect a stamp to take 1 minute, I'm
> > not going to get bent out of shape if it takes 5 minutes to deliver.  If
> > messages are time-critical, make sure the recipient has you whitelisted
> Well if the postage generation is done in the background probably
> doesn't matter so much.  (Though there is some user expectation
> potential problem -- eg dialup, I want to know when its gone so I can
> hangup).

Well that's a problem, but minting could also take much longer than
expected with sub-puzzles.  Unless common stamp values are so small they
have six-sigma time bounds of 10-20 seconds, I don't think foreground
stamp generation would fly.  I suspect that's near 20 bits at the moment,
for most desktop machines.

"Not your decision to make."
"Yes.  But it's the right decision, and I made it for my daughter."
 - Bill, Beatrix; Kill Bill Vol. 2

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