Annotation of www/crypto.html, Revision 1.18
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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
1.16 deraadt 35: licenses because we do not wish to break the laws of any country.
36: The cryptographic software components which we use currently were
37: written in Argentina, Australia, Canada, Germany, Greece, Norway, and
38: Sweden.
39: <p>
1.7 deraadt 40:
1.15 deraadt 41: When we create OpenBSD releases or snapshots we build our release
42: binaries in free countries to assure that the sources and binaries we
43: provide to users are free of tainting. In the past our release binary
44: builds have been done in Canada, Sweden, and Germany.<p>
45:
1.16 deraadt 46: OpenBSD ships with Kerberos IV included. The codebase we use is the
1.17 deraadt 47: exportable KTH-based release from Sweden. Our X11 source has been
48: extended to make use of Kerberos IV as well. Kerberos V support will
1.16 deraadt 49: perhaps appear in 1999, but at present time a freely exportable
50: Kerberos V release does not exist.<p>
51:
1.15 deraadt 52: Today cryptography is an important means for enhancing the <a
53: href=security.html>security</a> of an operating system. The
54: cryptography utilized in OpenBSD can be classified into three
55: different aspects:<p>
1.10 deraadt 56:
57: <ul>
1.11 deraadt 58: <li><a href=#prng>Pseudo Random Number Generators</a> (PRNG): ARC4, ...
59: <li><a href=#hash>Cryptographic Hash Functions</a>: MD5, SHA1, ...
60: <li><a href=#trans>Cryptographic Transforms</a>: DES, Blowfish, ...
1.10 deraadt 61: </ul>
62:
63: <p>
1.18 ! deraadt 64: <a name=prng></a>
1.10 deraadt 65: <h3><font color=#e00000><strong>Pseudo Random Number Generators</strong></font></h3>
66: A Pseudo Random Number Generator (PRNG) provides applications with a stream of
67: numbers which have certain important properties for system security:<p>
68:
69: <ul>
1.11 deraadt 70: <li>It should be impossible for an outsider to predict the output of the
71: random number generator even with knowledge of previous output.
72: <li>The generated numbers should not have repeating patterns which means
73: the PRNG should have a very long cycle length.
1.10 deraadt 74: </ul>
75:
1.13 deraadt 76: A PRNG is normally just an algorithm where the same initial starting
77: values will yield the same sequence of outputs. On a multiuser
78: operating system there are many sources which allow seeding the PRNG
79: with random data. The OpenBSD kernel uses the mouse interrupt timing,
80: network data interrupt latency, inter-keypress timing and disk IO
81: information to fill an entropy pool. Random numbers are available for
82: kernel routines and are exported via devices to userland programs.
83: So far random numbers are used in the following places<p>
84:
1.10 deraadt 85: <ul>
1.14 deraadt 86: <li>Dynamic sin_port allocation in bind(2).
87: <li>PIDs of processes.
88: <li>RPC transaction IDs (XID).
89: <li>NFS RPC transaction IDs (XID).
90: <li>DNS Query-IDs.
91: <li>Inode generation numbers, see getfh(2) and fsirand(8).
92: <li>Timing perturbance in traceroute(1).
93: <li>Stronger temporary names for mktemp(3) and mkstemp(3)
94: <li>Randomness added to the TCP ISS value for protection against
95: spoofing attacks.
96: <li>To generate salts for the various password algorithms.
97: <li>For generating fake S/Key challenges.
1.10 deraadt 98: </ul>
1.1 deraadt 99:
1.10 deraadt 100: <p>
1.18 ! deraadt 101: <a name=hash></a>
1.10 deraadt 102: <h3><font color=#e00000><strong>Cryptographic Hash Functions</strong></font></h3>
103: A Hash Function compresses its input data to a string of
104: constant size. For a Cryptographic Hash Function it is infeasible to find
1.1 deraadt 105: <ul>
1.11 deraadt 106: <li>two inputs which have the same output (collision resistant),
107: <li>a different input for a given input with the same output
108: (2nd preimage resistant).
1.1 deraadt 109: </ul>
1.10 deraadt 110:
1.12 millert 111: In OpenBSD MD5, SHA1, and RIPEMD-160 are used as Cryptographic Hash Functions,
112: e.g.
1.10 deraadt 113: <ul>
1.14 deraadt 114: <li>In S/Key support to provide one time passwords.
115: <li>In <a href=http://wserver.physnet.uni-hamburg.de/provos/photuris/>
1.10 deraadt 116: IPSec or Photuris</a> to authenticate the data origin of packets
117: and to ensure packet integrity.
1.14 deraadt 118: <li>For FreeBSD-style MD5 passwords (not enabled by default).
119: <li>For TCP SYN cookie support (not enabled by default).
1.10 deraadt 120: </ul>
121:
1.6 deraadt 122: <p>
1.18 ! deraadt 123: <a name=trans></a>
1.10 deraadt 124: <h3><font color=#e00000><strong>Cryptographic Transforms</strong></font></h3>
1.11 deraadt 125: Cryptographic Transforms are used to encrypt and decrypt data. These
126: are normally used with an encryption key for data encryption and with
127: a decryption key for data decryption. The security of a Cryptographic
128: Transform should rely only on the keying material.<p>
1.6 deraadt 129:
1.11 deraadt 130: OpenBSD provides transforms like DES and Blowfish for the kernel and userland
131: programs, which are used in many places like
1.10 deraadt 132: <ul>
1.14 deraadt 133: <li>In libc for creating Blowfish passwords.
134: <li>In <a href=http://wserver.physnet.uni-hamburg.de/provos/photuris/>IPSec</a>
135: to provide confidentiality for the network layer.
136: <li>In kerberized telnet.
137: <li>In Photuris to protect the exchanged packet content.
1.10 deraadt 138: </ul>
1.1 deraadt 139:
1.10 deraadt 140: <p>
1.1 deraadt 141: <hr>
1.10 deraadt 142: <a href=/index.html><img src=/back.gif border=0 alt=OpenBSD></a>
143: <a href=mailto:www@openbsd.org>www@openbsd.org</a>
144: <br>
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