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Revision 1.7 Revision 1.8
1GLEP: 59 1GLEP: 59
2Title: Manifest2 hash policies and security implications 2Title: Manifest2 hash policies and security implications
3Version: $Revision: 1.7 $ 3Version: $Revision: 1.8 $
4Last-Modified: $Date: 2010/02/02 05:49:27 $ 4Last-Modified: $Date: 2010/02/07 10:39:52 $
5Author: Robin Hugh Johnson <robbat2@gentoo.org>, 5Author: Robin Hugh Johnson <robbat2@gentoo.org>,
6Status: Draft 6Status: Draft
7Type: Standards Track 7Type: Standards Track
8Content-Type: text/x-rst 8Content-Type: text/x-rst
9Requires: 44 9Requires: 44
56by Wang et al [W04], the time required to break MD5 has been massively 56by Wang et al [W04], the time required to break MD5 has been massively
57reduced. Originally at 1 hour on a near-supercomputer (IBM P690) and 57reduced. Originally at 1 hour on a near-supercomputer (IBM P690) and
58estimated at 64 hours with a Pentium-3 1.7Ghz. This has gone down to 58estimated at 64 hours with a Pentium-3 1.7Ghz. This has gone down to
59less than in two years, to 17 seconds [K06a]. 59less than in two years, to 17 seconds [K06a].
60 60
6108/2004 - 1 hour, IBM pSeries 690 (32x 1.7Ghz POWER4+) = 54.4 GHz-Hours 61- 08/2004 - 1 hour, IBM pSeries 690 (32x 1.7Ghz POWER4+) = 54.4 GHz-Hours
62
6203/2005 - 8 hours, Pentium-M 1.6Ghz = 12.8 Ghz-Hours 63- 03/2005 - 8 hours, Pentium-M 1.6Ghz = 12.8 Ghz-Hours
64
6311/2005 - 5 hours, Pentium-4 1.7Ghz = 8.5 Ghz-Hours 65- 11/2005 - 5 hours, Pentium-4 1.7Ghz = 8.5 Ghz-Hours
66
6403/2006 - 1 minute, Pentium-4 3.2Ghz = .05 Ghz-Hours 67- 03/2006 - 1 minute, Pentium-4 3.2Ghz = .05 Ghz-Hours
68
6504/2006 - 17 seconds, Pentium-4 3.2Ghz = .01 Ghz-Hours 69- 04/2006 - 17 seconds, Pentium-4 3.2Ghz = .01 Ghz-Hours
66 70
67If we accept a factor of 800x as a sample of how much faster a checksum 71If we accept a factor of 800x as a sample of how much faster a checksum
68may be broken over the course of 2 years (MD5 using the above data is 72may be broken over the course of 2 years (MD5 using the above data is
69>2000x), then existing checksums do not stand a significant chance of 73>2000x), then existing checksums do not stand a significant chance of
70survival in the future. We should thus accept that whatever checksums we 74survival in the future. We should thus accept that whatever checksums we
94------------------- 98-------------------
95Portage should always try to verify all supported hashes that are 99Portage should always try to verify all supported hashes that are
96available in a Manifest2, starting with the strongest ones as maintained 100available in a Manifest2, starting with the strongest ones as maintained
97by a preference list. Over time, the weaker checksums should be removed 101by a preference list. Over time, the weaker checksums should be removed
98from Manifest2 files, once all old Portage installations have had 102from Manifest2 files, once all old Portage installations have had
99sufficient time to upgrade. We should be prepared to add stronger 103sufficient time to upgrade. Stronger checksums shall be added as soon as
100checksums wherever possible, and to remove those that have been 104an implementation is available in Portage. Weak checksums may be removed
101defeated. 105as long as the depreciation process is followed (see below).
102 106
103As soon as feasible, we should add the SHA512 and WHIRLPOOL algorithms. 107As soon as feasible, we should add the SHA512 and WHIRLPOOL algorithms.
104In future, as stream-based checksums are developed (in response to the 108In future, as stream-based checksums are developed (in response to the
105development by NIST [AHS]), they should be considered and used. 109development by NIST [AHS]), they should be considered and used.
106 110
115The existence unsupported hash is not considered to be a failure unless 119The existence unsupported hash is not considered to be a failure unless
116no supported hashes are available for a given Manifest entry. 120no supported hashes are available for a given Manifest entry.
117 121
118Checksum depreciation timing 122Checksum depreciation timing
119---------------------------- 123----------------------------
124General principles:
125~~~~~~~~~~~~~~~~~~~
126A minimum set of depreciated checksums shall be maintained only to
127support old package manager versions where needed by historically used
128trees:
129
130- New package manager versions should NOT use depreciated checksums in
131
132- New trees with that have never used the depreciated checksums may omit
133 them for reasons of size, but are still strongly suggested to include
134 them.
135
136- Removal of depreciated checksums shall happen after no less than 18
137 months or one major Portage version cycle, whichever is greater.
138
139Immediate plans:
140~~~~~~~~~~~~~~~~
120For the current Portage, both SHA1 and RIPEMD160 should be immediately 141For the current Portage, both SHA1 and RIPEMD160 should be immediately
121removed, as they present no advantages over the already present SHA256. 142removed, as they present no advantages over the already present SHA256.
122SHA256 cannot be replaced immediately with SHA512, as existing Portage 143SHA256 cannot be replaced immediately with SHA512, as existing Portage
123versions need at least one supported algorithm present (SHA256 support 144versions need at least one supported algorithm present (SHA256 support
124was added in June 2006), so it must be retained for some while. 145was added in June 2006), so it must be retained for some while.
125 146
126Immediately: 147Immediately:
148
127- Add WHIRLPOOL and SHA512. 149- Add WHIRLPOOL and SHA512.
150
128- Remove SHA1 and RIPEMD160. 151- Remove SHA1 and RIPEMD160.
129 152
130After the majority of Portage installations include SHA512 support: 153After the majority of Portage installations include SHA512 support:
154
131- Remove SHA256. 155- Remove SHA256.
132 156
133Backwards Compatibility 157Backwards Compatibility
134======================= 158=======================
135Old versions of Portage may support and expect only specific checksums. 159Old versions of Portage may support and expect only specific checksums.

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