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author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 18:20:36 -0400 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 18:20:36 -0400 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/crypto/api-intro.txt |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
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1 | |||
2 | Scatterlist Cryptographic API | ||
3 | |||
4 | INTRODUCTION | ||
5 | |||
6 | The Scatterlist Crypto API takes page vectors (scatterlists) as | ||
7 | arguments, and works directly on pages. In some cases (e.g. ECB | ||
8 | mode ciphers), this will allow for pages to be encrypted in-place | ||
9 | with no copying. | ||
10 | |||
11 | One of the initial goals of this design was to readily support IPsec, | ||
12 | so that processing can be applied to paged skb's without the need | ||
13 | for linearization. | ||
14 | |||
15 | |||
16 | DETAILS | ||
17 | |||
18 | At the lowest level are algorithms, which register dynamically with the | ||
19 | API. | ||
20 | |||
21 | 'Transforms' are user-instantiated objects, which maintain state, handle all | ||
22 | of the implementation logic (e.g. manipulating page vectors), provide an | ||
23 | abstraction to the underlying algorithms, and handle common logical | ||
24 | operations (e.g. cipher modes, HMAC for digests). However, at the user | ||
25 | level they are very simple. | ||
26 | |||
27 | Conceptually, the API layering looks like this: | ||
28 | |||
29 | [transform api] (user interface) | ||
30 | [transform ops] (per-type logic glue e.g. cipher.c, digest.c) | ||
31 | [algorithm api] (for registering algorithms) | ||
32 | |||
33 | The idea is to make the user interface and algorithm registration API | ||
34 | very simple, while hiding the core logic from both. Many good ideas | ||
35 | from existing APIs such as Cryptoapi and Nettle have been adapted for this. | ||
36 | |||
37 | The API currently supports three types of transforms: Ciphers, Digests and | ||
38 | Compressors. The compression algorithms especially seem to be performing | ||
39 | very well so far. | ||
40 | |||
41 | Support for hardware crypto devices via an asynchronous interface is | ||
42 | under development. | ||
43 | |||
44 | Here's an example of how to use the API: | ||
45 | |||
46 | #include <linux/crypto.h> | ||
47 | |||
48 | struct scatterlist sg[2]; | ||
49 | char result[128]; | ||
50 | struct crypto_tfm *tfm; | ||
51 | |||
52 | tfm = crypto_alloc_tfm("md5", 0); | ||
53 | if (tfm == NULL) | ||
54 | fail(); | ||
55 | |||
56 | /* ... set up the scatterlists ... */ | ||
57 | |||
58 | crypto_digest_init(tfm); | ||
59 | crypto_digest_update(tfm, &sg, 2); | ||
60 | crypto_digest_final(tfm, result); | ||
61 | |||
62 | crypto_free_tfm(tfm); | ||
63 | |||
64 | |||
65 | Many real examples are available in the regression test module (tcrypt.c). | ||
66 | |||
67 | |||
68 | CONFIGURATION NOTES | ||
69 | |||
70 | As Triple DES is part of the DES module, for those using modular builds, | ||
71 | add the following line to /etc/modprobe.conf: | ||
72 | |||
73 | alias des3_ede des | ||
74 | |||
75 | The Null algorithms reside in the crypto_null module, so these lines | ||
76 | should also be added: | ||
77 | |||
78 | alias cipher_null crypto_null | ||
79 | alias digest_null crypto_null | ||
80 | alias compress_null crypto_null | ||
81 | |||
82 | The SHA384 algorithm shares code within the SHA512 module, so you'll | ||
83 | also need: | ||
84 | alias sha384 sha512 | ||
85 | |||
86 | |||
87 | DEVELOPER NOTES | ||
88 | |||
89 | Transforms may only be allocated in user context, and cryptographic | ||
90 | methods may only be called from softirq and user contexts. | ||
91 | |||
92 | When using the API for ciphers, performance will be optimal if each | ||
93 | scatterlist contains data which is a multiple of the cipher's block | ||
94 | size (typically 8 bytes). This prevents having to do any copying | ||
95 | across non-aligned page fragment boundaries. | ||
96 | |||
97 | |||
98 | ADDING NEW ALGORITHMS | ||
99 | |||
100 | When submitting a new algorithm for inclusion, a mandatory requirement | ||
101 | is that at least a few test vectors from known sources (preferably | ||
102 | standards) be included. | ||
103 | |||
104 | Converting existing well known code is preferred, as it is more likely | ||
105 | to have been reviewed and widely tested. If submitting code from LGPL | ||
106 | sources, please consider changing the license to GPL (see section 3 of | ||
107 | the LGPL). | ||
108 | |||
109 | Algorithms submitted must also be generally patent-free (e.g. IDEA | ||
110 | will not be included in the mainline until around 2011), and be based | ||
111 | on a recognized standard and/or have been subjected to appropriate | ||
112 | peer review. | ||
113 | |||
114 | Also check for any RFCs which may relate to the use of specific algorithms, | ||
115 | as well as general application notes such as RFC2451 ("The ESP CBC-Mode | ||
116 | Cipher Algorithms"). | ||
117 | |||
118 | It's a good idea to avoid using lots of macros and use inlined functions | ||
119 | instead, as gcc does a good job with inlining, while excessive use of | ||
120 | macros can cause compilation problems on some platforms. | ||
121 | |||
122 | Also check the TODO list at the web site listed below to see what people | ||
123 | might already be working on. | ||
124 | |||
125 | |||
126 | BUGS | ||
127 | |||
128 | Send bug reports to: | ||
129 | James Morris <jmorris@redhat.com> | ||
130 | Cc: David S. Miller <davem@redhat.com> | ||
131 | |||
132 | |||
133 | FURTHER INFORMATION | ||
134 | |||
135 | For further patches and various updates, including the current TODO | ||
136 | list, see: | ||
137 | http://samba.org/~jamesm/crypto/ | ||
138 | |||
139 | |||
140 | AUTHORS | ||
141 | |||
142 | James Morris | ||
143 | David S. Miller | ||
144 | |||
145 | |||
146 | CREDITS | ||
147 | |||
148 | The following people provided invaluable feedback during the development | ||
149 | of the API: | ||
150 | |||
151 | Alexey Kuznetzov | ||
152 | Rusty Russell | ||
153 | Herbert Valerio Riedel | ||
154 | Jeff Garzik | ||
155 | Michael Richardson | ||
156 | Andrew Morton | ||
157 | Ingo Oeser | ||
158 | Christoph Hellwig | ||
159 | |||
160 | Portions of this API were derived from the following projects: | ||
161 | |||
162 | Kerneli Cryptoapi (http://www.kerneli.org/) | ||
163 | Alexander Kjeldaas | ||
164 | Herbert Valerio Riedel | ||
165 | Kyle McMartin | ||
166 | Jean-Luc Cooke | ||
167 | David Bryson | ||
168 | Clemens Fruhwirth | ||
169 | Tobias Ringstrom | ||
170 | Harald Welte | ||
171 | |||
172 | and; | ||
173 | |||
174 | Nettle (http://www.lysator.liu.se/~nisse/nettle/) | ||
175 | Niels Möller | ||
176 | |||
177 | Original developers of the crypto algorithms: | ||
178 | |||
179 | Dana L. How (DES) | ||
180 | Andrew Tridgell and Steve French (MD4) | ||
181 | Colin Plumb (MD5) | ||
182 | Steve Reid (SHA1) | ||
183 | Jean-Luc Cooke (SHA256, SHA384, SHA512) | ||
184 | Kazunori Miyazawa / USAGI (HMAC) | ||
185 | Matthew Skala (Twofish) | ||
186 | Dag Arne Osvik (Serpent) | ||
187 | Brian Gladman (AES) | ||
188 | Kartikey Mahendra Bhatt (CAST6) | ||
189 | Jon Oberheide (ARC4) | ||
190 | Jouni Malinen (Michael MIC) | ||
191 | |||
192 | SHA1 algorithm contributors: | ||
193 | Jean-Francois Dive | ||
194 | |||
195 | DES algorithm contributors: | ||
196 | Raimar Falke | ||
197 | Gisle Sælensminde | ||
198 | Niels Möller | ||
199 | |||
200 | Blowfish algorithm contributors: | ||
201 | Herbert Valerio Riedel | ||
202 | Kyle McMartin | ||
203 | |||
204 | Twofish algorithm contributors: | ||
205 | Werner Koch | ||
206 | Marc Mutz | ||
207 | |||
208 | SHA256/384/512 algorithm contributors: | ||
209 | Andrew McDonald | ||
210 | Kyle McMartin | ||
211 | Herbert Valerio Riedel | ||
212 | |||
213 | AES algorithm contributors: | ||
214 | Alexander Kjeldaas | ||
215 | Herbert Valerio Riedel | ||
216 | Kyle McMartin | ||
217 | Adam J. Richter | ||
218 | Fruhwirth Clemens (i586) | ||
219 | Linus Torvalds (i586) | ||
220 | |||
221 | CAST5 algorithm contributors: | ||
222 | Kartikey Mahendra Bhatt (original developers unknown, FSF copyright). | ||
223 | |||
224 | TEA/XTEA algorithm contributors: | ||
225 | Aaron Grothe | ||
226 | |||
227 | Khazad algorithm contributors: | ||
228 | Aaron Grothe | ||
229 | |||
230 | Whirlpool algorithm contributors: | ||
231 | Aaron Grothe | ||
232 | Jean-Luc Cooke | ||
233 | |||
234 | Anubis algorithm contributors: | ||
235 | Aaron Grothe | ||
236 | |||
237 | Tiger algorithm contributors: | ||
238 | Aaron Grothe | ||
239 | |||
240 | Generic scatterwalk code by Adam J. Richter <adam@yggdrasil.com> | ||
241 | |||
242 | Please send any credits updates or corrections to: | ||
243 | James Morris <jmorris@redhat.com> | ||
244 | |||