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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/crypto
downloadlinux-linaro-android-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz
Linux-2.6.12-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!
Diffstat (limited to 'Documentation/crypto')
-rw-r--r--Documentation/crypto/api-intro.txt244
-rw-r--r--Documentation/crypto/descore-readme.txt352
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+
+ Scatterlist Cryptographic API
+
+INTRODUCTION
+
+The Scatterlist Crypto API takes page vectors (scatterlists) as
+arguments, and works directly on pages. In some cases (e.g. ECB
+mode ciphers), this will allow for pages to be encrypted in-place
+with no copying.
+
+One of the initial goals of this design was to readily support IPsec,
+so that processing can be applied to paged skb's without the need
+for linearization.
+
+
+DETAILS
+
+At the lowest level are algorithms, which register dynamically with the
+API.
+
+'Transforms' are user-instantiated objects, which maintain state, handle all
+of the implementation logic (e.g. manipulating page vectors), provide an
+abstraction to the underlying algorithms, and handle common logical
+operations (e.g. cipher modes, HMAC for digests). However, at the user
+level they are very simple.
+
+Conceptually, the API layering looks like this:
+
+ [transform api] (user interface)
+ [transform ops] (per-type logic glue e.g. cipher.c, digest.c)
+ [algorithm api] (for registering algorithms)
+
+The idea is to make the user interface and algorithm registration API
+very simple, while hiding the core logic from both. Many good ideas
+from existing APIs such as Cryptoapi and Nettle have been adapted for this.
+
+The API currently supports three types of transforms: Ciphers, Digests and
+Compressors. The compression algorithms especially seem to be performing
+very well so far.
+
+Support for hardware crypto devices via an asynchronous interface is
+under development.
+
+Here's an example of how to use the API:
+
+ #include <linux/crypto.h>
+
+ struct scatterlist sg[2];
+ char result[128];
+ struct crypto_tfm *tfm;
+
+ tfm = crypto_alloc_tfm("md5", 0);
+ if (tfm == NULL)
+ fail();
+
+ /* ... set up the scatterlists ... */
+
+ crypto_digest_init(tfm);
+ crypto_digest_update(tfm, &sg, 2);
+ crypto_digest_final(tfm, result);
+
+ crypto_free_tfm(tfm);
+
+
+Many real examples are available in the regression test module (tcrypt.c).
+
+
+CONFIGURATION NOTES
+
+As Triple DES is part of the DES module, for those using modular builds,
+add the following line to /etc/modprobe.conf:
+
+ alias des3_ede des
+
+The Null algorithms reside in the crypto_null module, so these lines
+should also be added:
+
+ alias cipher_null crypto_null
+ alias digest_null crypto_null
+ alias compress_null crypto_null
+
+The SHA384 algorithm shares code within the SHA512 module, so you'll
+also need:
+ alias sha384 sha512
+
+
+DEVELOPER NOTES
+
+Transforms may only be allocated in user context, and cryptographic
+methods may only be called from softirq and user contexts.
+
+When using the API for ciphers, performance will be optimal if each
+scatterlist contains data which is a multiple of the cipher's block
+size (typically 8 bytes). This prevents having to do any copying
+across non-aligned page fragment boundaries.
+
+
+ADDING NEW ALGORITHMS
+
+When submitting a new algorithm for inclusion, a mandatory requirement
+is that at least a few test vectors from known sources (preferably
+standards) be included.
+
+Converting existing well known code is preferred, as it is more likely
+to have been reviewed and widely tested. If submitting code from LGPL
+sources, please consider changing the license to GPL (see section 3 of
+the LGPL).
+
+Algorithms submitted must also be generally patent-free (e.g. IDEA
+will not be included in the mainline until around 2011), and be based
+on a recognized standard and/or have been subjected to appropriate
+peer review.
+
+Also check for any RFCs which may relate to the use of specific algorithms,
+as well as general application notes such as RFC2451 ("The ESP CBC-Mode
+Cipher Algorithms").
+
+It's a good idea to avoid using lots of macros and use inlined functions
+instead, as gcc does a good job with inlining, while excessive use of
+macros can cause compilation problems on some platforms.
+
+Also check the TODO list at the web site listed below to see what people
+might already be working on.
+
+
+BUGS
+
+Send bug reports to:
+James Morris <jmorris@redhat.com>
+Cc: David S. Miller <davem@redhat.com>
+
+
+FURTHER INFORMATION
+
+For further patches and various updates, including the current TODO
+list, see:
+http://samba.org/~jamesm/crypto/
+
+
+AUTHORS
+
+James Morris
+David S. Miller
+
+
+CREDITS
+
+The following people provided invaluable feedback during the development
+of the API:
+
+ Alexey Kuznetzov
+ Rusty Russell
+ Herbert Valerio Riedel
+ Jeff Garzik
+ Michael Richardson
+ Andrew Morton
+ Ingo Oeser
+ Christoph Hellwig
+
+Portions of this API were derived from the following projects:
+
+ Kerneli Cryptoapi (http://www.kerneli.org/)
+ Alexander Kjeldaas
+ Herbert Valerio Riedel
+ Kyle McMartin
+ Jean-Luc Cooke
+ David Bryson
+ Clemens Fruhwirth
+ Tobias Ringstrom
+ Harald Welte
+
+and;
+
+ Nettle (http://www.lysator.liu.se/~nisse/nettle/)
+ Niels Möller
+
+Original developers of the crypto algorithms:
+
+ Dana L. How (DES)
+ Andrew Tridgell and Steve French (MD4)
+ Colin Plumb (MD5)
+ Steve Reid (SHA1)
+ Jean-Luc Cooke (SHA256, SHA384, SHA512)
+ Kazunori Miyazawa / USAGI (HMAC)
+ Matthew Skala (Twofish)
+ Dag Arne Osvik (Serpent)
+ Brian Gladman (AES)
+ Kartikey Mahendra Bhatt (CAST6)
+ Jon Oberheide (ARC4)
+ Jouni Malinen (Michael MIC)
+
+SHA1 algorithm contributors:
+ Jean-Francois Dive
+
+DES algorithm contributors:
+ Raimar Falke
+ Gisle Sælensminde
+ Niels Möller
+
+Blowfish algorithm contributors:
+ Herbert Valerio Riedel
+ Kyle McMartin
+
+Twofish algorithm contributors:
+ Werner Koch
+ Marc Mutz
+
+SHA256/384/512 algorithm contributors:
+ Andrew McDonald
+ Kyle McMartin
+ Herbert Valerio Riedel
+
+AES algorithm contributors:
+ Alexander Kjeldaas
+ Herbert Valerio Riedel
+ Kyle McMartin
+ Adam J. Richter
+ Fruhwirth Clemens (i586)
+ Linus Torvalds (i586)
+
+CAST5 algorithm contributors:
+ Kartikey Mahendra Bhatt (original developers unknown, FSF copyright).
+
+TEA/XTEA algorithm contributors:
+ Aaron Grothe
+
+Khazad algorithm contributors:
+ Aaron Grothe
+
+Whirlpool algorithm contributors:
+ Aaron Grothe
+ Jean-Luc Cooke
+
+Anubis algorithm contributors:
+ Aaron Grothe
+
+Tiger algorithm contributors:
+ Aaron Grothe
+
+Generic scatterwalk code by Adam J. Richter <adam@yggdrasil.com>
+
+Please send any credits updates or corrections to:
+James Morris <jmorris@redhat.com>
+
diff --git a/Documentation/crypto/descore-readme.txt b/Documentation/crypto/descore-readme.txt
new file mode 100644
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+Below is the orginal README file from the descore.shar package.
+------------------------------------------------------------------------------
+
+des - fast & portable DES encryption & decryption.
+Copyright (C) 1992 Dana L. How
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Library General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+Author's address: how@isl.stanford.edu
+
+$Id: README,v 1.15 1992/05/20 00:25:32 how E $
+
+
+==>> To compile after untarring/unsharring, just `make' <<==
+
+
+This package was designed with the following goals:
+1. Highest possible encryption/decryption PERFORMANCE.
+2. PORTABILITY to any byte-addressable host with a 32bit unsigned C type
+3. Plug-compatible replacement for KERBEROS's low-level routines.
+
+This second release includes a number of performance enhancements for
+register-starved machines. My discussions with Richard Outerbridge,
+71755.204@compuserve.com, sparked a number of these enhancements.
+
+To more rapidly understand the code in this package, inspect desSmallFips.i
+(created by typing `make') BEFORE you tackle desCode.h. The latter is set
+up in a parameterized fashion so it can easily be modified by speed-daemon
+hackers in pursuit of that last microsecond. You will find it more
+illuminating to inspect one specific implementation,
+and then move on to the common abstract skeleton with this one in mind.
+
+
+performance comparison to other available des code which i could
+compile on a SPARCStation 1 (cc -O4, gcc -O2):
+
+this code (byte-order independent):
+ 30us per encryption (options: 64k tables, no IP/FP)
+ 33us per encryption (options: 64k tables, FIPS standard bit ordering)
+ 45us per encryption (options: 2k tables, no IP/FP)
+ 48us per encryption (options: 2k tables, FIPS standard bit ordering)
+ 275us to set a new key (uses 1k of key tables)
+ this has the quickest encryption/decryption routines i've seen.
+ since i was interested in fast des filters rather than crypt(3)
+ and password cracking, i haven't really bothered yet to speed up
+ the key setting routine. also, i have no interest in re-implementing
+ all the other junk in the mit kerberos des library, so i've just
+ provided my routines with little stub interfaces so they can be
+ used as drop-in replacements with mit's code or any of the mit-
+ compatible packages below. (note that the first two timings above
+ are highly variable because of cache effects).
+
+kerberos des replacement from australia (version 1.95):
+ 53us per encryption (uses 2k of tables)
+ 96us to set a new key (uses 2.25k of key tables)
+ so despite the author's inclusion of some of the performance
+ improvements i had suggested to him, this package's
+ encryption/decryption is still slower on the sparc and 68000.
+ more specifically, 19-40% slower on the 68020 and 11-35% slower
+ on the sparc, depending on the compiler;
+ in full gory detail (ALT_ECB is a libdes variant):
+ compiler machine desCore libdes ALT_ECB slower by
+ gcc 2.1 -O2 Sun 3/110 304 uS 369.5uS 461.8uS 22%
+ cc -O1 Sun 3/110 336 uS 436.6uS 399.3uS 19%
+ cc -O2 Sun 3/110 360 uS 532.4uS 505.1uS 40%
+ cc -O4 Sun 3/110 365 uS 532.3uS 505.3uS 38%
+ gcc 2.1 -O2 Sun 4/50 48 uS 53.4uS 57.5uS 11%
+ cc -O2 Sun 4/50 48 uS 64.6uS 64.7uS 35%
+ cc -O4 Sun 4/50 48 uS 64.7uS 64.9uS 35%
+ (my time measurements are not as accurate as his).
+ the comments in my first release of desCore on version 1.92:
+ 68us per encryption (uses 2k of tables)
+ 96us to set a new key (uses 2.25k of key tables)
+ this is a very nice package which implements the most important
+ of the optimizations which i did in my encryption routines.
+ it's a bit weak on common low-level optimizations which is why
+ it's 39%-106% slower. because he was interested in fast crypt(3) and
+ password-cracking applications, he also used the same ideas to
+ speed up the key-setting routines with impressive results.
+ (at some point i may do the same in my package). he also implements
+ the rest of the mit des library.
+ (code from eay@psych.psy.uq.oz.au via comp.sources.misc)
+
+fast crypt(3) package from denmark:
+ the des routine here is buried inside a loop to do the
+ crypt function and i didn't feel like ripping it out and measuring
+ performance. his code takes 26 sparc instructions to compute one
+ des iteration; above, Quick (64k) takes 21 and Small (2k) takes 37.
+ he claims to use 280k of tables but the iteration calculation seems
+ to use only 128k. his tables and code are machine independent.
+ (code from glad@daimi.aau.dk via alt.sources or comp.sources.misc)
+
+swedish reimplementation of Kerberos des library
+ 108us per encryption (uses 34k worth of tables)
+ 134us to set a new key (uses 32k of key tables to get this speed!)
+ the tables used seem to be machine-independent;
+ he seems to have included a lot of special case code
+ so that, e.g., `long' loads can be used instead of 4 `char' loads
+ when the machine's architecture allows it.
+ (code obtained from chalmers.se:pub/des)
+
+crack 3.3c package from england:
+ as in crypt above, the des routine is buried in a loop. it's
+ also very modified for crypt. his iteration code uses 16k
+ of tables and appears to be slow.
+ (code obtained from aem@aber.ac.uk via alt.sources or comp.sources.misc)
+
+``highly optimized'' and tweaked Kerberos/Athena code (byte-order dependent):
+ 165us per encryption (uses 6k worth of tables)
+ 478us to set a new key (uses <1k of key tables)
+ so despite the comments in this code, it was possible to get
+ faster code AND smaller tables, as well as making the tables
+ machine-independent.
+ (code obtained from prep.ai.mit.edu)
+
+UC Berkeley code (depends on machine-endedness):
+ 226us per encryption
+10848us to set a new key
+ table sizes are unclear, but they don't look very small
+ (code obtained from wuarchive.wustl.edu)
+
+
+motivation and history
+
+a while ago i wanted some des routines and the routines documented on sun's
+man pages either didn't exist or dumped core. i had heard of kerberos,
+and knew that it used des, so i figured i'd use its routines. but once
+i got it and looked at the code, it really set off a lot of pet peeves -
+it was too convoluted, the code had been written without taking
+advantage of the regular structure of operations such as IP, E, and FP
+(i.e. the author didn't sit down and think before coding),
+it was excessively slow, the author had attempted to clarify the code
+by adding MORE statements to make the data movement more `consistent'
+instead of simplifying his implementation and cutting down on all data
+movement (in particular, his use of L1, R1, L2, R2), and it was full of
+idiotic `tweaks' for particular machines which failed to deliver significant
+speedups but which did obfuscate everything. so i took the test data
+from his verification program and rewrote everything else.
+
+a while later i ran across the great crypt(3) package mentioned above.
+the fact that this guy was computing 2 sboxes per table lookup rather
+than one (and using a MUCH larger table in the process) emboldened me to
+do the same - it was a trivial change from which i had been scared away
+by the larger table size. in his case he didn't realize you don't need to keep
+the working data in TWO forms, one for easy use of half the sboxes in
+indexing, the other for easy use of the other half; instead you can keep
+it in the form for the first half and use a simple rotate to get the other
+half. this means i have (almost) half the data manipulation and half
+the table size. in fairness though he might be encoding something particular
+to crypt(3) in his tables - i didn't check.
+
+i'm glad that i implemented it the way i did, because this C version is
+portable (the ifdef's are performance enhancements) and it is faster
+than versions hand-written in assembly for the sparc!
+
+
+porting notes
+
+one thing i did not want to do was write an enormous mess
+which depended on endedness and other machine quirks,
+and which necessarily produced different code and different lookup tables
+for different machines. see the kerberos code for an example
+of what i didn't want to do; all their endedness-specific `optimizations'
+obfuscate the code and in the end were slower than a simpler machine
+independent approach. however, there are always some portability
+considerations of some kind, and i have included some options
+for varying numbers of register variables.
+perhaps some will still regard the result as a mess!
+
+1) i assume everything is byte addressable, although i don't actually
+ depend on the byte order, and that bytes are 8 bits.
+ i assume word pointers can be freely cast to and from char pointers.
+ note that 99% of C programs make these assumptions.
+ i always use unsigned char's if the high bit could be set.
+2) the typedef `word' means a 32 bit unsigned integral type.
+ if `unsigned long' is not 32 bits, change the typedef in desCore.h.
+ i assume sizeof(word) == 4 EVERYWHERE.
+
+the (worst-case) cost of my NOT doing endedness-specific optimizations
+in the data loading and storing code surrounding the key iterations
+is less than 12%. also, there is the added benefit that
+the input and output work areas do not need to be word-aligned.
+
+
+OPTIONAL performance optimizations
+
+1) you should define one of `i386,' `vax,' `mc68000,' or `sparc,'
+ whichever one is closest to the capabilities of your machine.
+ see the start of desCode.h to see exactly what this selection implies.
+ note that if you select the wrong one, the des code will still work;
+ these are just performance tweaks.
+2) for those with functional `asm' keywords: you should change the
+ ROR and ROL macros to use machine rotate instructions if you have them.
+ this will save 2 instructions and a temporary per use,
+ or about 32 to 40 instructions per en/decryption.
+ note that gcc is smart enough to translate the ROL/R macros into
+ machine rotates!
+
+these optimizations are all rather persnickety, yet with them you should
+be able to get performance equal to assembly-coding, except that:
+1) with the lack of a bit rotate operator in C, rotates have to be synthesized
+ from shifts. so access to `asm' will speed things up if your machine
+ has rotates, as explained above in (3) (not necessary if you use gcc).
+2) if your machine has less than 12 32-bit registers i doubt your compiler will
+ generate good code.
+ `i386' tries to configure the code for a 386 by only declaring 3 registers
+ (it appears that gcc can use ebx, esi and edi to hold register variables).
+ however, if you like assembly coding, the 386 does have 7 32-bit registers,
+ and if you use ALL of them, use `scaled by 8' address modes with displacement
+ and other tricks, you can get reasonable routines for DesQuickCore... with
+ about 250 instructions apiece. For DesSmall... it will help to rearrange
+ des_keymap, i.e., now the sbox # is the high part of the index and
+ the 6 bits of data is the low part; it helps to exchange these.
+ since i have no way to conveniently test it i have not provided my
+ shoehorned 386 version. note that with this release of desCore, gcc is able
+ to put everything in registers(!), and generate about 370 instructions apiece
+ for the DesQuickCore... routines!
+
+coding notes
+
+the en/decryption routines each use 6 necessary register variables,
+with 4 being actively used at once during the inner iterations.
+if you don't have 4 register variables get a new machine.
+up to 8 more registers are used to hold constants in some configurations.
+
+i assume that the use of a constant is more expensive than using a register:
+a) additionally, i have tried to put the larger constants in registers.
+ registering priority was by the following:
+ anything more than 12 bits (bad for RISC and CISC)
+ greater than 127 in value (can't use movq or byte immediate on CISC)
+ 9-127 (may not be able to use CISC shift immediate or add/sub quick),
+ 1-8 were never registered, being the cheapest constants.
+b) the compiler may be too stupid to realize table and table+256 should
+ be assigned to different constant registers and instead repetitively
+ do the arithmetic, so i assign these to explicit `m' register variables
+ when possible and helpful.
+
+i assume that indexing is cheaper or equivalent to auto increment/decrement,
+where the index is 7 bits unsigned or smaller.
+this assumption is reversed for 68k and vax.
+
+i assume that addresses can be cheaply formed from two registers,
+or from a register and a small constant.
+for the 68000, the `two registers and small offset' form is used sparingly.
+all index scaling is done explicitly - no hidden shifts by log2(sizeof).
+
+the code is written so that even a dumb compiler
+should never need more than one hidden temporary,
+increasing the chance that everything will fit in the registers.
+KEEP THIS MORE SUBTLE POINT IN MIND IF YOU REWRITE ANYTHING.
+(actually, there are some code fragments now which do require two temps,
+but fixing it would either break the structure of the macros or
+require declaring another temporary).
+
+
+special efficient data format
+
+bits are manipulated in this arrangement most of the time (S7 S5 S3 S1):
+ 003130292827xxxx242322212019xxxx161514131211xxxx080706050403xxxx
+(the x bits are still there, i'm just emphasizing where the S boxes are).
+bits are rotated left 4 when computing S6 S4 S2 S0:
+ 282726252423xxxx201918171615xxxx121110090807xxxx040302010031xxxx
+the rightmost two bits are usually cleared so the lower byte can be used
+as an index into an sbox mapping table. the next two x'd bits are set
+to various values to access different parts of the tables.
+
+
+how to use the routines
+
+datatypes:
+ pointer to 8 byte area of type DesData
+ used to hold keys and input/output blocks to des.
+
+ pointer to 128 byte area of type DesKeys
+ used to hold full 768-bit key.
+ must be long-aligned.
+
+DesQuickInit()
+ call this before using any other routine with `Quick' in its name.
+ it generates the special 64k table these routines need.
+DesQuickDone()
+ frees this table
+
+DesMethod(m, k)
+ m points to a 128byte block, k points to an 8 byte des key
+ which must have odd parity (or -1 is returned) and which must
+ not be a (semi-)weak key (or -2 is returned).
+ normally DesMethod() returns 0.
+ m is filled in from k so that when one of the routines below
+ is called with m, the routine will act like standard des
+ en/decryption with the key k. if you use DesMethod,
+ you supply a standard 56bit key; however, if you fill in
+ m yourself, you will get a 768bit key - but then it won't
+ be standard. it's 768bits not 1024 because the least significant
+ two bits of each byte are not used. note that these two bits
+ will be set to magic constants which speed up the encryption/decryption
+ on some machines. and yes, each byte controls
+ a specific sbox during a specific iteration.
+ you really shouldn't use the 768bit format directly; i should
+ provide a routine that converts 128 6-bit bytes (specified in
+ S-box mapping order or something) into the right format for you.
+ this would entail some byte concatenation and rotation.
+
+Des{Small|Quick}{Fips|Core}{Encrypt|Decrypt}(d, m, s)
+ performs des on the 8 bytes at s into the 8 bytes at d. (d,s: char *).
+ uses m as a 768bit key as explained above.
+ the Encrypt|Decrypt choice is obvious.
+ Fips|Core determines whether a completely standard FIPS initial
+ and final permutation is done; if not, then the data is loaded
+ and stored in a nonstandard bit order (FIPS w/o IP/FP).
+ Fips slows down Quick by 10%, Small by 9%.
+ Small|Quick determines whether you use the normal routine
+ or the crazy quick one which gobbles up 64k more of memory.
+ Small is 50% slower then Quick, but Quick needs 32 times as much
+ memory. Quick is included for programs that do nothing but DES,
+ e.g., encryption filters, etc.
+
+
+Getting it to compile on your machine
+
+there are no machine-dependencies in the code (see porting),
+except perhaps the `now()' macro in desTest.c.
+ALL generated tables are machine independent.
+you should edit the Makefile with the appropriate optimization flags
+for your compiler (MAX optimization).
+
+
+Speeding up kerberos (and/or its des library)
+
+note that i have included a kerberos-compatible interface in desUtil.c
+through the functions des_key_sched() and des_ecb_encrypt().
+to use these with kerberos or kerberos-compatible code put desCore.a
+ahead of the kerberos-compatible library on your linker's command line.
+you should not need to #include desCore.h; just include the header
+file provided with the kerberos library.
+
+Other uses
+
+the macros in desCode.h would be very useful for putting inline des
+functions in more complicated encryption routines.