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<div class="moz-cite-prefix">You are missing the following:<br>
Files are encrypted for deduplication. That implies a way to
derive a key from the content of the files. That is if two files
are similar they will have similar ciphertexts <br>
and subsequently as proposed equivalent pads since the pad would
be the result of a PRNG seeded under the same deterministic key.<br>
So in our case we are discussing not for 11 & 12 but for 11
& 11 or 12 & 12.<br>
<br>
Regards,<br>
<br>
Iraklis<br>
On 07/12/2013 11:27 AM, Olaf TNSB wrote:<br>
</div>
<blockquote
cite="mid:CABDMPbqeg-haz6vif9nWoEEXriiXud9JH=y9r_OjxK7RNaG+fQ@mail.gmail.com"
type="cite">
<p>Am I missing something simple here? You pad pre-encryption and
unless the encryption algorithm is completely flawed then
slightly different input files will give completely different
output.</p>
<p>In a similar (but entirely unrelated way!) look at the
MD5/SHA256/your-fav-hash-function of the numbers 11 & 12. Do
you see any similarities in the hash?<br>
</p>
<p>Olaf</p>
<div class="gmail_quote">On 12/07/2013 5:58 PM, "Iraklis ." <<a
moz-do-not-send="true" href="mailto:leontiad@gmail.com">leontiad@gmail.com</a>>
wrote:<br type="attribution">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
<div>But still someone can identify the common pattern at
the end of two or more similar files so the pad can be
detected and deleted, thus length is not hidden.<br>
On 07/11/2013 09:01 PM, Tony Arcieri wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">On Wed, Jul 10, 2013 at 7:31 AM, Ed
Kapitein <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:ed@kapitein.org" target="_blank">ed@kapitein.org</a>></span>
wrote:<br>
<div class="gmail_extra">
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><span style="color:rgb(34,34,34)">Hi Zooko,</span><br>
</div>
<br>
Be careful with zero padding, it might leave the
data open for a<br>
watermarking attack.<br>
</blockquote>
<div><br>
</div>
<div>How about padding with the output of a PRNG
seeded with the content hash? That way it'd still
be deterministic</div>
</div>
<div><br>
</div>
-- <br>
Tony Arcieri<br>
</div>
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