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25<tbody valign="top"> 25<tbody valign="top">
26<tr class="field"><th class="field-name">GLEP:</th><td class="field-body">59</td> 26<tr class="field"><th class="field-name">GLEP:</th><td class="field-body">59</td>
27</tr> 27</tr>
28<tr class="field"><th class="field-name">Title:</th><td class="field-body">Manifest2 hash policies and security implications</td> 28<tr class="field"><th class="field-name">Title:</th><td class="field-body">Manifest2 hash policies and security implications</td>
29</tr> 29</tr>
30<tr class="field"><th class="field-name">Version:</th><td class="field-body">1.5</td> 30<tr class="field"><th class="field-name">Version:</th><td class="field-body">1.7</td>
31</tr> 31</tr>
32<tr class="field"><th class="field-name">Last-Modified:</th><td class="field-body"><a class="reference external" href="http://www.gentoo.org/cgi-bin/viewcvs.cgi/xml/htdocs/proj/en/glep/glep-0059.txt?cvsroot=gentoo">2010/01/31 07:55:45</a></td> 32<tr class="field"><th class="field-name">Last-Modified:</th><td class="field-body"><a class="reference external" href="http://www.gentoo.org/cgi-bin/viewcvs.cgi/xml/htdocs/proj/en/glep/glep-0059.txt?cvsroot=gentoo">2010/02/02 05:49:27</a></td>
33</tr> 33</tr>
34<tr class="field"><th class="field-name">Author:</th><td class="field-body">Robin Hugh Johnson &lt;robbat2&#32;&#97;t&#32;gentoo.org&gt;,</td> 34<tr class="field"><th class="field-name">Author:</th><td class="field-body">Robin Hugh Johnson &lt;robbat2&#32;&#97;t&#32;gentoo.org&gt;,</td>
35</tr> 35</tr>
36<tr class="field"><th class="field-name">Status:</th><td class="field-body">Draft</td> 36<tr class="field"><th class="field-name">Status:</th><td class="field-body">Draft</td>
37</tr> 37</tr>
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60<li><a class="reference internal" href="#specification" id="id3">Specification</a><ul> 60<li><a class="reference internal" href="#specification" id="id3">Specification</a><ul>
61<li><a class="reference internal" href="#the-bad-news" id="id4">The bad news</a></li> 61<li><a class="reference internal" href="#the-bad-news" id="id4">The bad news</a></li>
62<li><a class="reference internal" href="#how-fast-can-md5-be-broken" id="id5">How fast can MD5 be broken?</a></li> 62<li><a class="reference internal" href="#how-fast-can-md5-be-broken" id="id5">How fast can MD5 be broken?</a></li>
63<li><a class="reference internal" href="#the-good-news" id="id6">The good news</a></li> 63<li><a class="reference internal" href="#the-good-news" id="id6">The good news</a></li>
64<li><a class="reference internal" href="#what-should-be-done" id="id7">What should be done</a></li> 64<li><a class="reference internal" href="#what-should-be-done" id="id7">What should be done</a></li>
65<li><a class="reference internal" href="#checksum-depreciation-timing" id="id8">Checksum depreciation timing</a></li> 65<li><a class="reference internal" href="#checksum-depreciation-timing" id="id8">Checksum depreciation timing</a><ul>
66<li><a class="reference internal" href="#general-principles" id="id9">General principles:</a></li>
67<li><a class="reference internal" href="#immediate-plans" id="id10">Immediate plans:</a></li>
66</ul> 68</ul>
67</li> 69</li>
70</ul>
71</li>
68<li><a class="reference internal" href="#backwards-compatibility" id="id9">Backwards Compatibility</a></li> 72<li><a class="reference internal" href="#backwards-compatibility" id="id11">Backwards Compatibility</a></li>
69<li><a class="reference internal" href="#references" id="id10">References</a></li> 73<li><a class="reference internal" href="#references" id="id12">References</a></li>
70<li><a class="reference internal" href="#thanks-to" id="id11">Thanks to</a></li> 74<li><a class="reference internal" href="#thanks-to" id="id13">Thanks to</a></li>
71<li><a class="reference internal" href="#copyright" id="id12">Copyright</a></li> 75<li><a class="reference internal" href="#copyright" id="id14">Copyright</a></li>
72</ul> 76</ul>
73</div> 77</div>
74<div class="section" id="abstract"> 78<div class="section" id="abstract">
75<h1><a class="toc-backref" href="#id1">Abstract</a></h1> 79<h1><a class="toc-backref" href="#id1">Abstract</a></h1>
76<p>While Manifest2 format allows multiple hashes, the question of which 80<p>While Manifest2 format allows multiple hashes, the question of which
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83<h1><a class="toc-backref" href="#id2">Motivation</a></h1> 87<h1><a class="toc-backref" href="#id2">Motivation</a></h1>
84<p>This GLEP is being written as part of the work on signing the Portage 88<p>This GLEP is being written as part of the work on signing the Portage
85tree, but is only tangentially related to the actual signing of 89tree, but is only tangentially related to the actual signing of
86Manifests. Checksums present one possible weak point in the overall 90Manifests. Checksums present one possible weak point in the overall
87security of the tree - and a comprehensive security plan is needed.</p> 91security of the tree - and a comprehensive security plan is needed.</p>
92<p>This GLEP is not mandatory for the tree-signing specification, but
93instead aims to improve the security of the hashes used in Manifest2.
94As such, it is also able to stand on it's own.</p>
88</div> 95</div>
89<div class="section" id="specification"> 96<div class="section" id="specification">
90<h1><a class="toc-backref" href="#id3">Specification</a></h1> 97<h1><a class="toc-backref" href="#id3">Specification</a></h1>
91<div class="section" id="the-bad-news"> 98<div class="section" id="the-bad-news">
92<h2><a class="toc-backref" href="#id4">The bad news</a></h2> 99<h2><a class="toc-backref" href="#id4">The bad news</a></h2>
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109<p>For a general collision, not a pre-image attack, since the announcement 116<p>For a general collision, not a pre-image attack, since the announcement
110by Wang et al [W04], the time required to break MD5 has been massively 117by Wang et al [W04], the time required to break MD5 has been massively
111reduced. Originally at 1 hour on a near-supercomputer (IBM P690) and 118reduced. Originally at 1 hour on a near-supercomputer (IBM P690) and
112estimated at 64 hours with a Pentium-3 1.7Ghz. This has gone down to 119estimated at 64 hours with a Pentium-3 1.7Ghz. This has gone down to
113less than in two years, to 17 seconds [K06a].</p> 120less than in two years, to 17 seconds [K06a].</p>
121<ul class="simple">
114<p>08/2004 - 1 hour, IBM pSeries 690 (32x 1.7Ghz POWER4+) = 54.4 GHz-Hours 122<li>08/2004 - 1 hour, IBM pSeries 690 (32x 1.7Ghz POWER4+) = 54.4 GHz-Hours</li>
11503/2005 - 8 hours, Pentium-M 1.6Ghz = 12.8 Ghz-Hours 123<li>03/2005 - 8 hours, Pentium-M 1.6Ghz = 12.8 Ghz-Hours</li>
11611/2005 - 5 hours, Pentium-4 1.7Ghz = 8.5 Ghz-Hours 124<li>11/2005 - 5 hours, Pentium-4 1.7Ghz = 8.5 Ghz-Hours</li>
11703/2006 - 1 minute, Pentium-4 3.2Ghz = .05 Ghz-Hours 125<li>03/2006 - 1 minute, Pentium-4 3.2Ghz = .05 Ghz-Hours</li>
11804/2006 - 17 seconds, Pentium-4 3.2Ghz = .01 Ghz-Hours</p> 126<li>04/2006 - 17 seconds, Pentium-4 3.2Ghz = .01 Ghz-Hours</li>
127</ul>
119<p>If we accept a factor of 800x as a sample of how much faster a checksum 128<p>If we accept a factor of 800x as a sample of how much faster a checksum
120may be broken over the course of 2 years (MD5 using the above data is 129may be broken over the course of 2 years (MD5 using the above data is
121&gt;2000x), then existing checksums do not stand a significant chance of 130&gt;2000x), then existing checksums do not stand a significant chance of
122survival in the future. We should thus accept that whatever checksums we 131survival in the future. We should thus accept that whatever checksums we
123are using today, will be broken in the near future, and plan as best as 132are using today, will be broken in the near future, and plan as best as
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144<h2><a class="toc-backref" href="#id7">What should be done</a></h2> 153<h2><a class="toc-backref" href="#id7">What should be done</a></h2>
145<p>Portage should always try to verify all supported hashes that are 154<p>Portage should always try to verify all supported hashes that are
146available in a Manifest2, starting with the strongest ones as maintained 155available in a Manifest2, starting with the strongest ones as maintained
147by a preference list. Over time, the weaker checksums should be removed 156by a preference list. Over time, the weaker checksums should be removed
148from Manifest2 files, once all old Portage installations have had 157from Manifest2 files, once all old Portage installations have had
149sufficient time to upgrade. We should be prepared to add stronger 158sufficient time to upgrade. Stronger checksums shall be added as soon as
150checksums wherever possible, and to remove those that have been 159an implementation is available in Portage. Weak checksums may be removed
151defeated.</p> 160as long as the depreciation process is followed (see below).</p>
152<p>As soon as feasible, we should add the SHA512 and WHIRLPOOL algorithms. 161<p>As soon as feasible, we should add the SHA512 and WHIRLPOOL algorithms.
153In future, as stream-based checksums are developed (in response to the 162In future, as stream-based checksums are developed (in response to the
154development by NIST [AHS]), they should be considered and used.</p> 163development by NIST [AHS]), they should be considered and used.</p>
155<p>The SHA512 algorithm is available in Python 2.5, which has been a 164<p>The SHA512 algorithm is available in Python 2.5, which has been a
156dependency of Portage since approximately Python 2.1.6.13.</p> 165dependency of Portage since approximately Portage 2.1.6.13.</p>
157<p>The WHIRLPOOL checksum is not available within the PyCrypto library or 166<p>The WHIRLPOOL checksum is not available within the PyCrypto library or
158hashlib that is part of Python 2.5, but there are multiple alternative 167hashlib that is part of Python 2.5, but there are multiple alternative
159Python implementations available, ranging from pure Python to C-based 168Python implementations available, ranging from pure Python to C-based
160(python-mhash).</p> 169(python-mhash).</p>
161<p>The existence unsupported hash is not considered to be a failure unless 170<p>The existence unsupported hash is not considered to be a failure unless
162no supported hashes are available for a given Manifest entry.</p> 171no supported hashes are available for a given Manifest entry.</p>
163</div> 172</div>
164<div class="section" id="checksum-depreciation-timing"> 173<div class="section" id="checksum-depreciation-timing">
165<h2><a class="toc-backref" href="#id8">Checksum depreciation timing</a></h2> 174<h2><a class="toc-backref" href="#id8">Checksum depreciation timing</a></h2>
175<div class="section" id="general-principles">
176<h3><a class="toc-backref" href="#id9">General principles:</a></h3>
177<p>A minimum set of depreciated checksums shall be maintained only to
178support old package manager versions where needed by historically used
179trees:</p>
180<ul class="simple">
181<li>New package manager versions should NOT use depreciated checksums in</li>
182<li>New trees with that have never used the depreciated checksums may omit
183them for reasons of size, but are still strongly suggested to include
184them.</li>
185<li>Removal of depreciated checksums shall happen after no less than 18
186months or one major Portage version cycle, whichever is greater.</li>
187</ul>
188</div>
189<div class="section" id="immediate-plans">
190<h3><a class="toc-backref" href="#id10">Immediate plans:</a></h3>
166<p>For the current Portage, both SHA1 and RIPEMD160 should be immediately 191<p>For the current Portage, both SHA1 and RIPEMD160 should be immediately
167removed, as they present no advantages over the already present SHA256. 192removed, as they present no advantages over the already present SHA256.
168SHA256 cannot be replaced immediately with SHA512, as existing Portage 193SHA256 cannot be replaced immediately with SHA512, as existing Portage
169versions need at least one supported algorithm present (SHA256 support 194versions need at least one supported algorithm present (SHA256 support
170was added in June 2006), so it must be retained for some while.</p> 195was added in June 2006), so it must be retained for some while.</p>
171<p>Immediately: 196<p>Immediately:</p>
197<ul class="simple">
172- Add WHIRLPOOL and SHA512. 198<li>Add WHIRLPOOL and SHA512.</li>
173- Remove SHA1 and RIPEMD160.</p> 199<li>Remove SHA1 and RIPEMD160.</li>
200</ul>
174<p>After the majority of Portage installations include SHA512 support: 201<p>After the majority of Portage installations include SHA512 support:</p>
202<ul class="simple">
175- Remove SHA256.</p> 203<li>Remove SHA256.</li>
204</ul>
205</div>
176</div> 206</div>
177</div> 207</div>
178<div class="section" id="backwards-compatibility"> 208<div class="section" id="backwards-compatibility">
179<h1><a class="toc-backref" href="#id9">Backwards Compatibility</a></h1> 209<h1><a class="toc-backref" href="#id11">Backwards Compatibility</a></h1>
180<p>Old versions of Portage may support and expect only specific checksums. 210<p>Old versions of Portage may support and expect only specific checksums.
181This is accounted for in the checksum depreciation discussion.</p> 211This is accounted for in the checksum depreciation discussion.</p>
212<p>For maximum compatiability, we should only have to include each of the
213old algorithms that we are officially still supporting, as well as the
214new ones that we prefer.</p>
182</div> 215</div>
183<div class="section" id="references"> 216<div class="section" id="references">
184<h1><a class="toc-backref" href="#id10">References</a></h1> 217<h1><a class="toc-backref" href="#id12">References</a></h1>
185<dl class="docutils"> 218<dl class="docutils">
186<dt>[AHS] NIST (2007). &quot;NIST's Plan for New Cryptographic Hash Functions&quot;,</dt> 219<dt>[AHS] NIST (2007). &quot;NIST's Plan for New Cryptographic Hash Functions&quot;,</dt>
187<dd>(Advanced Hash Standard). <a class="reference external" href="http://csrc.nist.gov/pki/HashWorkshop/">http://csrc.nist.gov/pki/HashWorkshop/</a></dd> 220<dd>(Advanced Hash Standard). <a class="reference external" href="http://csrc.nist.gov/pki/HashWorkshop/">http://csrc.nist.gov/pki/HashWorkshop/</a></dd>
188<dt>[BOBO06] Boneh, D. and Boyen, X. (2006). &quot;On the Impossibility of</dt> 221<dt>[BOBO06] Boneh, D. and Boyen, X. (2006). &quot;On the Impossibility of</dt>
189<dd>Efficiently Combining Collision Resistant Hash Functions&quot;; Proceedings 222<dd>Efficiently Combining Collision Resistant Hash Functions&quot;; Proceedings
… …
217version (August 17, 2004). Available online from: 250version (August 17, 2004). Available online from:
218<a class="reference external" href="http://eprint.iacr.org/2004/199.pdf">http://eprint.iacr.org/2004/199.pdf</a></dd> 251<a class="reference external" href="http://eprint.iacr.org/2004/199.pdf">http://eprint.iacr.org/2004/199.pdf</a></dd>
219</dl> 252</dl>
220</div> 253</div>
221<div class="section" id="thanks-to"> 254<div class="section" id="thanks-to">
222<h1><a class="toc-backref" href="#id11">Thanks to</a></h1> 255<h1><a class="toc-backref" href="#id13">Thanks to</a></h1>
223<dl class="docutils"> 256<dl class="docutils">
224<dt>I'd like to thank the following folks, in no specific order:</dt> 257<dt>I'd like to thank the following folks, in no specific order:</dt>
225<dd><ul class="first last simple"> 258<dd><ul class="first last simple">
226<li>Ciaran McCreesh (ciaranm) - for pointing out the Joux (2004) paper, 259<li>Ciaran McCreesh (ciaranm) - for pointing out the Joux (2004) paper,
227and also being stubborn enough in not accepting a partial solution.</li> 260and also being stubborn enough in not accepting a partial solution.</li>
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231</ul> 264</ul>
232</dd> 265</dd>
233</dl> 266</dl>
234</div> 267</div>
235<div class="section" id="copyright"> 268<div class="section" id="copyright">
236<h1><a class="toc-backref" href="#id12">Copyright</a></h1> 269<h1><a class="toc-backref" href="#id14">Copyright</a></h1>
237<p>Copyright (c) 2006-2010 by Robin Hugh Johnson. This material may be 270<p>Copyright (c) 2006-2010 by Robin Hugh Johnson. This material may be
238distributed only subject to the terms and conditions set forth in the 271distributed only subject to the terms and conditions set forth in the
239Open Publication License, v1.0.</p> 272Open Publication License, v1.0.</p>
240<p>vim: tw=72 ts=2 expandtab:</p> 273<p>vim: tw=72 ts=2 expandtab:</p>
241</div> 274</div>
242 275
243</div> 276</div>
244<div class="footer"> 277<div class="footer">
245<hr class="footer" /> 278<hr class="footer" />
246<a class="reference external" href="glep-0059.txt">View document source</a>. 279<a class="reference external" href="glep-0059.txt">View document source</a>.
247Generated on: 2010-01-31 08:27 UTC. 280Generated on: 2010-02-07 10:37 UTC.
248Generated by <a class="reference external" href="http://docutils.sourceforge.net/">Docutils</a> from <a class="reference external" href="http://docutils.sourceforge.net/rst.html">reStructuredText</a> source. 281Generated by <a class="reference external" href="http://docutils.sourceforge.net/">Docutils</a> from <a class="reference external" href="http://docutils.sourceforge.net/rst.html">reStructuredText</a> source.
249 282
250</div> 283</div>
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