Annotation of www/crypto.html, Revision 1.14
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1.10 deraadt 4: <title>Cryptography in OpenBSD</title>
1.1 deraadt 5: <link rev=made href=mailto:www@openbsd.org>
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1.10 deraadt 7: <meta name="description" content="OpenBSD cryptography">
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10: <meta name="copyright" content="This document copyright 1997 by OpenBSD.">
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17: <p>
18: <h3><font color=#e00000><strong>OpenBSD Cryptography</strong></font></h3>
19: The OpenBSD project is based in Canada.<p>
20:
1.2 deraadt 21: The <a href=http://axion.physics.ubc.ca/ECL.html>Export Control
1.3 deraadt 22: List of Canada</a> places no significant restriction on the export of
1.5 deraadt 23: cryptographic software, and is even more explicit about the free
24: export of freely-available cryptographic software. Marc Plumb has
25: done
1.2 deraadt 26: <a href=http://insight.mcmaster.ca/org/efc/pages/doc/crypto-export.html>
1.5 deraadt 27: some research to test the cryptographic laws.</a>
1.2 deraadt 28: <p>
1.1 deraadt 29:
1.3 deraadt 30: Hence the OpenBSD project has embedded cryptography into numerous places
31: in the operating system. We require that the cryptographic software we
32: use be <a href=policy.html>freely available and with good licenses</a>.
1.4 deraadt 33: We do not use cryptography with nasty patents.
1.13 deraadt 34: We also require that such software is from countries with useful export
1.7 deraadt 35: licenses because we do not wish to break the laws of any country.<p>
36:
1.10 deraadt 37: When we make OpenBSD releases or snapshots we do our build processes
38: in free countries to assure that the sources and binaries we provide
39: to users are free of tainting. In the past our release binary builds
40: have been done in Canada, Sweden, and Germany.<p>
41:
42: Today cryptography is an important mean for enhancing the security
43: of an operating system. The cryptography utilized in OpenBSD
44: can be classified into three different aspects:<p>
45:
46: <ul>
1.11 deraadt 47: <li><a href=#prng>Pseudo Random Number Generators</a> (PRNG): ARC4, ...
48: <li><a href=#hash>Cryptographic Hash Functions</a>: MD5, SHA1, ...
49: <li><a href=#trans>Cryptographic Transforms</a>: DES, Blowfish, ...
1.10 deraadt 50: </ul>
51:
52: <p>
53: <a name=prng>
54: <h3><font color=#e00000><strong>Pseudo Random Number Generators</strong></font></h3>
55: A Pseudo Random Number Generator (PRNG) provides applications with a stream of
56: numbers which have certain important properties for system security:<p>
57:
58: <ul>
1.11 deraadt 59: <li>It should be impossible for an outsider to predict the output of the
60: random number generator even with knowledge of previous output.
61: <li>The generated numbers should not have repeating patterns which means
62: the PRNG should have a very long cycle length.
1.10 deraadt 63: </ul>
64:
1.13 deraadt 65: A PRNG is normally just an algorithm where the same initial starting
66: values will yield the same sequence of outputs. On a multiuser
67: operating system there are many sources which allow seeding the PRNG
68: with random data. The OpenBSD kernel uses the mouse interrupt timing,
69: network data interrupt latency, inter-keypress timing and disk IO
70: information to fill an entropy pool. Random numbers are available for
71: kernel routines and are exported via devices to userland programs.
72: So far random numbers are used in the following places<p>
73:
1.10 deraadt 74: <ul>
1.14 ! deraadt 75: <li>Dynamic sin_port allocation in bind(2).
! 76: <li>PIDs of processes.
! 77: <li>RPC transaction IDs (XID).
! 78: <li>NFS RPC transaction IDs (XID).
! 79: <li>DNS Query-IDs.
! 80: <li>Inode generation numbers, see getfh(2) and fsirand(8).
! 81: <li>Timing perturbance in traceroute(1).
! 82: <li>Stronger temporary names for mktemp(3) and mkstemp(3)
! 83: <li>Randomness added to the TCP ISS value for protection against
! 84: spoofing attacks.
! 85: <li>To generate salts for the various password algorithms.
! 86: <li>For generating fake S/Key challenges.
1.10 deraadt 87: </ul>
1.1 deraadt 88:
1.10 deraadt 89: <p>
90: <a name=hash>
91: <h3><font color=#e00000><strong>Cryptographic Hash Functions</strong></font></h3>
92: A Hash Function compresses its input data to a string of
93: constant size. For a Cryptographic Hash Function it is infeasible to find
1.1 deraadt 94: <ul>
1.11 deraadt 95: <li>two inputs which have the same output (collision resistant),
96: <li>a different input for a given input with the same output
97: (2nd preimage resistant).
1.1 deraadt 98: </ul>
1.10 deraadt 99:
1.12 millert 100: In OpenBSD MD5, SHA1, and RIPEMD-160 are used as Cryptographic Hash Functions,
101: e.g.
1.10 deraadt 102: <ul>
1.14 ! deraadt 103: <li>In S/Key support to provide one time passwords.
! 104: <li>In <a href=http://wserver.physnet.uni-hamburg.de/provos/photuris/>
1.10 deraadt 105: IPSec or Photuris</a> to authenticate the data origin of packets
106: and to ensure packet integrity.
1.14 ! deraadt 107: <li>For FreeBSD-style MD5 passwords (not enabled by default).
! 108: <li>For TCP SYN cookie support (not enabled by default).
1.10 deraadt 109: </ul>
110:
1.6 deraadt 111: <p>
1.10 deraadt 112: <a name=trans>
113: <h3><font color=#e00000><strong>Cryptographic Transforms</strong></font></h3>
1.11 deraadt 114: Cryptographic Transforms are used to encrypt and decrypt data. These
115: are normally used with an encryption key for data encryption and with
116: a decryption key for data decryption. The security of a Cryptographic
117: Transform should rely only on the keying material.<p>
1.6 deraadt 118:
1.11 deraadt 119: OpenBSD provides transforms like DES and Blowfish for the kernel and userland
120: programs, which are used in many places like
1.10 deraadt 121: <ul>
1.14 ! deraadt 122: <li>In libc for creating Blowfish passwords.
! 123: <li>In <a href=http://wserver.physnet.uni-hamburg.de/provos/photuris/>IPSec</a>
! 124: to provide confidentiality for the network layer.
! 125: <li>In kerberized telnet.
! 126: <li>In Photuris to protect the exchanged packet content.
1.10 deraadt 127: </ul>
1.1 deraadt 128:
1.10 deraadt 129: <p>
1.1 deraadt 130: <hr>
1.10 deraadt 131: <a href=/index.html><img src=/back.gif border=0 alt=OpenBSD></a>
132: <a href=mailto:www@openbsd.org>www@openbsd.org</a>
133: <br>
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1.1 deraadt 135:
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