Because it's trivial to create collisions! You can choose exactly what output you want. That's why XOR is a very bad digest scheme.

- Sent from my phone

Den 4 feb 2014 14:20 skrev "Peter Todd" <pete@petertodd.org>:
On Tue, Feb 04, 2014 at 02:13:12PM +0100, Mike Hearn wrote:
> Hah, good point. If nobody completes the homework, I'll post a fixed
> version tomorrow :)

Heh, here's another 25mBTC while we're at it:

https://github.com/opentimestamps/opentimestamps-client/commit/288f3c17626974de7eaef4f1c9b5cd93eecf40f6

Why is that a bad idea?

Bonus question: What was I smoking? (hint: where do I live?)

> On Tue, Feb 4, 2014 at 2:03 PM, Peter Todd <pete@petertodd.org> wrote:
>
> > On Tue, Feb 04, 2014 at 01:01:12PM +0100, Mike Hearn wrote:
> > > Hello,
> > >
> > > I'm pleased to announce the release of bitcoinj 0.11, a library for
> > writing Bitcoin applications that run on the JVM. BitcoinJ is widely used
> > across the Bitcoin community; some users include Bitcoin Wallet for
> > Android, MultiBit, Hive, blockchain.info, the biteasy.com block explorer
> > (written in Lisp!), Circle, Neo/Bee (Cypriot payment network), bitpos.me,
> > Bitcoin Touch, BlueMatt's relay network and DNS crawler, academic advanced
> > contracts research and more.
> > >
> > > The release-0.11 git tag is signed by Andreas Schildbach's GPG key. The
> > commit hash is 410d4547a7dd. This paragraph is signed by the same Bitcoin
> > key as with previous releases (check their release announcements to
> > establish continuity). Additionally, this email is signed using DKIM and
> > for the first time, a key that was ID verified by the Swiss government.
> > >
> > > Key: 16vSNFP5Acsa6RBbjEA7QYCCRDRGXRFH4m
> > > Signature for last paragraph:
> > H3DvWBqFHPxKW/cdYUdZ6OHjbq6ZtC5PHK4ebpeiE+FqTHyRLJ58BItbC0R2vo77h+DthpQigdEZ0V8ivSM7VIg=
> >
> > The above makes for a great homework problem for budding cryptographers:
> > Why did the three forms of signature, DKIM, long-lived bitcoin address,
> > and Official Swiss Government Identity fail to let you actually verify
> > you have the right code? (but make for great security theater)
> >
> > Bonus question: Who has the smallest work-factor for such an attack?
> >
> > Two rewards of 25mBTC for correct responses to each question from a
> > crypto newbie.
> >
> > > Thanks to Mike Belshe, the wallet can now send to P2SH addresses.
> >
> > Thanks
> >
> > > Generated signatures now use canonical S values. This will aid a future
> > hard-forking rule change which bans malleable signatures.
> >
> > Soft-forking rule change.
> >
> > --
> > 'peter'[:-1]@petertodd.org
> > 000000000000000075829f6169c79d7d5aaa20bfa8da6e9edb2393c4f8662ba0
> >

--
'peter'[:-1]@petertodd.org
000000000000000075829f6169c79d7d5aaa20bfa8da6e9edb2393c4f8662ba0

------------------------------------------------------------------------------
Managing the Performance of Cloud-Based Applications
Take advantage of what the Cloud has to offer - Avoid Common Pitfalls.
Read the Whitepaper.
http://pubads.g.doubleclick.net/gampad/clk?id=121051231&iu=/4140/ostg.clktrk
_______________________________________________
Bitcoin-development mailing list
Bitcoin-development@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/bitcoin-development