Annotation of www/crypto.html, Revision 1.45
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1.45 ! deraadt 14: <img align=left alt="[OpenBSD]" height=166 width=197 SRC="images/blowfish-notext.jpg">
! 15: <br>
! 16: <br>
! 17: <br>
! 18: "The mantra of any good security engineer is: "Security is a not a
! 19: product, but a process." It's more than designing strong cryptography
! 20: into a system; it's designing the entire system such that all security
! 21: measures, including cryptography, work together."<br>
! 22: <br>
! 23: -- Bruce Schneier, author of "Applied Cryptography".
! 24: <br clear=all>
1.37 deraadt 25: <h2><font color=#e00000>Cryptography</font><hr></h2>
1.32 deraadt 26:
27: <strong>Index</strong><br>
1.41 louis 28: <a href=#why>Why do we ship cryptography?</a>.<br>
1.40 deraadt 29: <a href=#ssh>SSH soon built in</a>.<br>
1.32 deraadt 30: <a href=#prng>Pseudo Random Number Generators</a> (PRNG): ARC4, ...<br>
31: <a href=#hash>Cryptographic Hash Functions</a>: MD5, SHA1, ...<br>
32: <a href=#trans>Cryptographic Transforms</a>: DES, Blowfish, ...<br>
33:
34: <a href=#people>International Cryptographers wanted</a><br>
1.33 deraadt 35: <a href=#papers>Further Reading</a><br>
1.1 deraadt 36: <p>
1.32 deraadt 37: <hr>
38:
39: <a name=why></a>
1.42 deraadt 40: <h3><font color=#e00000>Why do we ship cryptography?</font></h3><p>
1.32 deraadt 41:
42: In three words: <strong>because we can</strong>.<p>
43:
1.1 deraadt 44: The OpenBSD project is based in Canada.<p>
45:
1.23 deraadt 46: The <a href=ECL.html>Export Control List of Canada</a>
47: places no significant restriction on the export of
1.5 deraadt 48: cryptographic software, and is even more explicit about the free
49: export of freely-available cryptographic software. Marc Plumb has
50: done
1.2 deraadt 51: <a href=http://insight.mcmaster.ca/org/efc/pages/doc/crypto-export.html>
1.31 aaron 52: some research to test the cryptographic laws</a>.
1.2 deraadt 53: <p>
1.1 deraadt 54:
1.3 deraadt 55: Hence the OpenBSD project has embedded cryptography into numerous places
56: in the operating system. We require that the cryptographic software we
57: use be <a href=policy.html>freely available and with good licenses</a>.
1.32 deraadt 58: We do not directly use cryptography with nasty patents.
1.13 deraadt 59: We also require that such software is from countries with useful export
1.16 deraadt 60: licenses because we do not wish to break the laws of any country.
61: The cryptographic software components which we use currently were
62: written in Argentina, Australia, Canada, Germany, Greece, Norway, and
63: Sweden.
64: <p>
1.7 deraadt 65:
1.15 deraadt 66: When we create OpenBSD releases or snapshots we build our release
67: binaries in free countries to assure that the sources and binaries we
68: provide to users are free of tainting. In the past our release binary
69: builds have been done in Canada, Sweden, and Germany.<p>
70:
1.16 deraadt 71: OpenBSD ships with Kerberos IV included. The codebase we use is the
1.17 deraadt 72: exportable KTH-based release from Sweden. Our X11 source has been
73: extended to make use of Kerberos IV as well. Kerberos V support will
1.16 deraadt 74: perhaps appear in 1999, but at present time a freely exportable
75: Kerberos V release does not exist.<p>
76:
1.15 deraadt 77: Today cryptography is an important means for enhancing the <a
78: href=security.html>security</a> of an operating system. The
1.42 deraadt 79: cryptography utilized in OpenBSD can be classified into various
80: aspects, described as follows.<p>
1.10 deraadt 81:
1.39 louis 82: <a name=ssh></a>
1.42 deraadt 83: <h3><font color=#e00000>SSH soon built in</font></h3><p>
1.39 louis 84:
1.40 deraadt 85: What is the first thing most people do after installing OpenBSD?
86: They install Secure Shell (ssh) from the ports tree or the packages on
87: the FTP sites. Until now, that is.<p>
1.39 louis 88:
89: This is still very much a work in progress, but we found an innovative way
1.40 deraadt 90: around the RSA patent. We are taking a free license release of ssh and
91: OpenBSD-ifying it. We will get around the USA-based RSA patent by providing
92: an easy way to automatically download and install a RSA-enabled package
1.41 louis 93: containing shared library versions of libcrypto and libssl. These packages
1.40 deraadt 94: are based on OpenSSL. People living outside the USA can freely use the
95: RSA patented code, while people inside the USA can freely use it for
96: non-commercial purposes. It appears as if companies inside the USA can
97: use the RSA libraries too, as long as RSA is not used in a profit generating
98: role.<p>
1.39 louis 99:
1.40 deraadt 100: But this way almost everyone will get ssh built-in.<p>
1.39 louis 101:
1.18 deraadt 102: <a name=prng></a>
1.42 deraadt 103: <h3><font color=#e00000>Pseudo Random Number Generators</font></h3><p>
1.32 deraadt 104:
1.10 deraadt 105: A Pseudo Random Number Generator (PRNG) provides applications with a stream of
106: numbers which have certain important properties for system security:<p>
107:
108: <ul>
1.11 deraadt 109: <li>It should be impossible for an outsider to predict the output of the
110: random number generator even with knowledge of previous output.
111: <li>The generated numbers should not have repeating patterns which means
112: the PRNG should have a very long cycle length.
1.10 deraadt 113: </ul>
1.32 deraadt 114: <p>
1.10 deraadt 115:
1.13 deraadt 116: A PRNG is normally just an algorithm where the same initial starting
117: values will yield the same sequence of outputs. On a multiuser
118: operating system there are many sources which allow seeding the PRNG
119: with random data. The OpenBSD kernel uses the mouse interrupt timing,
120: network data interrupt latency, inter-keypress timing and disk IO
121: information to fill an entropy pool. Random numbers are available for
122: kernel routines and are exported via devices to userland programs.
1.36 deraadt 123: So far random numbers are used in the following places:<p>
1.13 deraadt 124:
1.10 deraadt 125: <ul>
1.14 deraadt 126: <li>Dynamic sin_port allocation in bind(2).
127: <li>PIDs of processes.
1.26 aaron 128: <li>IP datagram IDs.
1.14 deraadt 129: <li>RPC transaction IDs (XID).
130: <li>NFS RPC transaction IDs (XID).
131: <li>DNS Query-IDs.
132: <li>Inode generation numbers, see getfh(2) and fsirand(8).
1.31 aaron 133: <li>Timing perturbance in traceroute(8).
1.14 deraadt 134: <li>Stronger temporary names for mktemp(3) and mkstemp(3)
135: <li>Randomness added to the TCP ISS value for protection against
136: spoofing attacks.
1.29 deraadt 137: <li>random padding in IPSEC esp_old packets.
1.14 deraadt 138: <li>To generate salts for the various password algorithms.
139: <li>For generating fake S/Key challenges.
1.44 provos 140: <li>In <a href=http://www.physnet.uni-hamburg.de/provos/photuris/>photurisd</a>
1.28 angelos 141: and <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=isakmpd>isakmpd</a>
142: to provide liveness proof of key exchanges.
1.10 deraadt 143: </ul>
1.1 deraadt 144:
1.10 deraadt 145: <p>
1.18 deraadt 146: <a name=hash></a>
1.42 deraadt 147: <h3><font color=#e00000>Cryptographic Hash Functions</font></h3><p>
1.32 deraadt 148:
1.10 deraadt 149: A Hash Function compresses its input data to a string of
1.36 deraadt 150: constant size. For a Cryptographic Hash Function it is infeasible to find:
151:
1.1 deraadt 152: <ul>
1.11 deraadt 153: <li>two inputs which have the same output (collision resistant),
154: <li>a different input for a given input with the same output
155: (2nd preimage resistant).
1.1 deraadt 156: </ul>
1.32 deraadt 157: <p>
1.10 deraadt 158:
1.12 millert 159: In OpenBSD MD5, SHA1, and RIPEMD-160 are used as Cryptographic Hash Functions,
1.36 deraadt 160: e.g:<p>
1.10 deraadt 161: <ul>
1.27 deraadt 162: <li>In <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=skey>S/Key</a>
163: to provide one time passwords.
164: <li>In <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=ipsec>IPsec</a>,
1.44 provos 165: <a href=http://www.physnet.uni-hamburg.de/provos/photuris/>photurisd</a>
1.27 deraadt 166: and
167: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=isakmpd>isakmpd(8)</a>
168: to authenticate the data origin of packets and to ensure packet integrity.
169: <li>For FreeBSD-style MD5 passwords (not enabled by default), see
170: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=passwd.conf&sektion=5>
171: passwd.conf(5)</a>
172: <li>For TCP SYN cookie support (not enabled by default), see
173: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=options&sektion=4>
174: options(4)</a>
1.24 niklas 175: <li>In libssl for digital signing of messages.
1.10 deraadt 176: </ul>
1.32 deraadt 177: <p>
1.10 deraadt 178:
1.6 deraadt 179: <p>
1.18 deraadt 180: <a name=trans></a>
1.42 deraadt 181: <h3><font color=#e00000>Cryptographic Transforms</font></h3><p>
1.32 deraadt 182:
1.11 deraadt 183: Cryptographic Transforms are used to encrypt and decrypt data. These
184: are normally used with an encryption key for data encryption and with
185: a decryption key for data decryption. The security of a Cryptographic
186: Transform should rely only on the keying material.<p>
1.6 deraadt 187:
1.24 niklas 188: OpenBSD provides transforms like DES, 3DES, Blowfish and Cast for the
1.36 deraadt 189: kernel and userland programs, which are used in many places like:<p>
1.10 deraadt 190: <ul>
1.27 deraadt 191: <li>In libc for creating
192: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=blf_key>Blowfish</a>
1.33 deraadt 193: passwords. See also the <a href=papers/bcrypt-paper.ps>USENIX paper</a>
194: on this topic.
1.27 deraadt 195: <li>In
196: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=ipsec>IPsec</a>
197: to provide confidentiality for the network layer.
198: <li>In Kerberos and a handful of kerberized applications, like
199: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=telnet>telnet</a>,
200: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=cvs>cvs</a>,
201: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=rsh>rsh</a>,
202: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=rcp>rcp</a>,
203: and
204: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=rlogin>rlogin</a>.
1.44 provos 205: <li>In <a href=http://www.physnet.uni-hamburg.de/provos/photuris/>
1.27 deraadt 206: photurisd</a> and
207: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=isakmpd>isakmpd</a>
208: to protect the exchanges where IPsec key material is negotiated.
1.24 niklas 209: <li>In AFS to protect the messages passing over the network, providing
1.27 deraadt 210: confidentiality of remote filesystem access.
1.24 niklas 211: <li>In libssl to let applications communicate over the de-facto standard
212: cryptographically secure SSL protocol.
1.10 deraadt 213: </ul>
1.1 deraadt 214:
1.10 deraadt 215: <p>
1.32 deraadt 216: <a name=people></a>
1.42 deraadt 217: <h3><font color=#e00000>International Cryptographers Wanted</font></h3><p>
1.32 deraadt 218:
219: Of course, our project needs people to work on these systems. If any
220: non-American cryptographer who meets the constraints listed earlier is
221: interested in helping out with embedded cryptography in OpenBSD,
222: please contact us.<p>
223:
1.33 deraadt 224: <p>
225: <a name=papers></a>
1.42 deraadt 226: <h3><font color=#e00000>Further Reading</font></h3><p>
1.33 deraadt 227:
228: A number of papers have been written by OpenBSD team members, about
229: cryptographic changes they have done in OpenBSD. The postscript
1.34 deraadt 230: versions of these documents are available as follows.<p>
1.33 deraadt 231:
232: <ul>
1.43 deraadt 233: <li>A Future-Adaptable Password Scheme.<br>
234: by <a href=mailto:provos@openbsd.org>Niels Provos<a/>,
235: <a href=mailto:dm@openbsd.org>David Mazieres</a>.<br>
1.33 deraadt 236: <a href=papers/bcrypt-paper.ps>paper</a> and
237: <a href=papers/bcrypt-slides.ps>slides</a>.
1.43 deraadt 238: <p>
239: <li>Cryptography in OpenBSD: An Overview.<br>
240: by <a href=mailto:deraadt@openbsd.org>Theo de Raadt</a>,
241: <a href=mailto:niklas@openbsd.org>Niklas Hallqvist</a>,
242: <a href=mailto:art@openbsd.org>Artur Grabowski</a>,
243: <a href=mailto:angelos@openbsd.org>Angelos D. Keromytis</a>,
244: <a href=mailto:provos@openbsd.org>Niels Provos</a>.<br>
1.33 deraadt 245: <a href=papers/crypt-paper.ps>paper</a> and
246: <a href=papers/crypt-slides.ps>slides</a>.
247: </ul>
248:
1.32 deraadt 249: <p>
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