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
>
>
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