<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=us-ascii">
<meta name=Generator content="Microsoft Word 11 (filtered medium)">
<!--[if !mso]>
<style>
v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style>
<![endif]-->
<style>
<!--
/* Font Definitions */
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman";}
a:link, span.MsoHyperlink
{color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{color:blue;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-reply;
font-family:Arial;
color:navy;}
@page Section1
{size:8.5in 11.0in;
margin:1.0in 1.25in 1.0in 1.25in;}
div.Section1
{page:Section1;}
-->
</style>
</head>
<body lang=EN-US link=blue vlink=blue>
<div class=Section1>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Hi Scal,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Can you give us some background of what
you are doing? Is this a school assignment? <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>If it is then maybe you could give us an
idea of what you do understand and what you do not, so that we can help either
with a discussion or suggestions for other reference material.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Ron Teitelbaum<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div style='border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt'>
<div>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center tabindex=-1>
</span></font></div>
<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
cryptography-bounces@lists.squeakfoundation.org
[mailto:cryptography-bounces@lists.squeakfoundation.org] <b><span
style='font-weight:bold'>On Behalf Of </span></b>scal rahotguy<br>
<b><span style='font-weight:bold'>Sent:</span></b> Tuesday, May 02, 2006 11:17
PM<br>
<b><span style='font-weight:bold'>To:</span></b>
Cryptography@lists.squeakfoundation.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> [Cryptography Team] Hash
function properties</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>For each of the following applications of hash functions, explain which
of hash function properties (preimage resistant, second preimage
resistant and collision resistant) are needed and which are not.<br>
<br>
<br>
(a) Cryptographic signatures are produced by computing a hash of a message,
then applying a signature function to the hash of the message. Suppose Eve has
a list of messages m1,...mn, and their signatures computed using Bob's signing
key, but does not have Bob's signing key. Assuming that the signature function
is not susceptible to attack, it should not be possible for Eve to present
Bob's signature on any message other than m1,...mn. <br>
<br>
(b) Suppose that Eve works for a Certificate Authority. She does not have
access to the special harware that computes digital signatures, but she knows
the hash function. In addition, Eve can get messages signed, but every message
that is signed automatically goes into a log file that Eve cannot change. Eve
should not be able to produce a certificate signed by the Certificate Authority
that does not appear in the log file. <br>
<br>
Anybody can explain these to me?<br>
<br>
thanks<br>
Akhil<o:p></o:p></span></font></p>
</div>
<p class=MsoNormal align=right style='text-align:right'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><a
href="http://www.unix.com/newreply.php?do=newreply&p=302072426"><span
style='text-decoration:none'><img border=0 width=70 height=22 id="_x0000_i1025"
src="http://www.unix.com/images/buttons/quote.gif" alt="Reply With Quote"
title="Reply With Quote"></span></a><o:p></o:p></span></font></p>
</div>
</div>
</body>
</html>