1Below is the original README file from the descore.shar package. 2------------------------------------------------------------------------------ 3 4des - fast & portable DES encryption & decryption. 5Copyright (C) 1992 Dana L. How 6 7This program is free software; you can redistribute it and/or modify 8it under the terms of the GNU Library General Public License as published by 9the Free Software Foundation; either version 2 of the License, or 10(at your option) any later version. 11 12This program is distributed in the hope that it will be useful, 13but WITHOUT ANY WARRANTY; without even the implied warranty of 14MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15GNU Library General Public License for more details. 16 17You should have received a copy of the GNU Library General Public License 18along with this program; if not, write to the Free Software 19Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 20 21Author's address: how@isl.stanford.edu 22 23$Id: README,v 1.15 1992/05/20 00:25:32 how E $ 24 25 26==>> To compile after untarring/unsharring, just `make' <<== 27 28 29This package was designed with the following goals: 301. Highest possible encryption/decryption PERFORMANCE. 312. PORTABILITY to any byte-addressable host with a 32bit unsigned C type 323. Plug-compatible replacement for KERBEROS's low-level routines. 33 34This second release includes a number of performance enhancements for 35register-starved machines. My discussions with Richard Outerbridge, 3671755.204@compuserve.com, sparked a number of these enhancements. 37 38To more rapidly understand the code in this package, inspect desSmallFips.i 39(created by typing `make') BEFORE you tackle desCode.h. The latter is set 40up in a parameterized fashion so it can easily be modified by speed-daemon 41hackers in pursuit of that last microsecond. You will find it more 42illuminating to inspect one specific implementation, 43and then move on to the common abstract skeleton with this one in mind. 44 45 46performance comparison to other available des code which i could 47compile on a SPARCStation 1 (cc -O4, gcc -O2): 48 49this code (byte-order independent): 50 30us per encryption (options: 64k tables, no IP/FP) 51 33us per encryption (options: 64k tables, FIPS standard bit ordering) 52 45us per encryption (options: 2k tables, no IP/FP) 53 48us per encryption (options: 2k tables, FIPS standard bit ordering) 54 275us to set a new key (uses 1k of key tables) 55 this has the quickest encryption/decryption routines i've seen. 56 since i was interested in fast des filters rather than crypt(3) 57 and password cracking, i haven't really bothered yet to speed up 58 the key setting routine. also, i have no interest in re-implementing 59 all the other junk in the mit kerberos des library, so i've just 60 provided my routines with little stub interfaces so they can be 61 used as drop-in replacements with mit's code or any of the mit- 62 compatible packages below. (note that the first two timings above 63 are highly variable because of cache effects). 64 65kerberos des replacement from australia (version 1.95): 66 53us per encryption (uses 2k of tables) 67 96us to set a new key (uses 2.25k of key tables) 68 so despite the author's inclusion of some of the performance 69 improvements i had suggested to him, this package's 70 encryption/decryption is still slower on the sparc and 68000. 71 more specifically, 19-40% slower on the 68020 and 11-35% slower 72 on the sparc, depending on the compiler; 73 in full gory detail (ALT_ECB is a libdes variant): 74 compiler machine desCore libdes ALT_ECB slower by 75 gcc 2.1 -O2 Sun 3/110 304 uS 369.5uS 461.8uS 22% 76 cc -O1 Sun 3/110 336 uS 436.6uS 399.3uS 19% 77 cc -O2 Sun 3/110 360 uS 532.4uS 505.1uS 40% 78 cc -O4 Sun 3/110 365 uS 532.3uS 505.3uS 38% 79 gcc 2.1 -O2 Sun 4/50 48 uS 53.4uS 57.5uS 11% 80 cc -O2 Sun 4/50 48 uS 64.6uS 64.7uS 35% 81 cc -O4 Sun 4/50 48 uS 64.7uS 64.9uS 35% 82 (my time measurements are not as accurate as his). 83 the comments in my first release of desCore on version 1.92: 84 68us per encryption (uses 2k of tables) 85 96us to set a new key (uses 2.25k of key tables) 86 this is a very nice package which implements the most important 87 of the optimizations which i did in my encryption routines. 88 it's a bit weak on common low-level optimizations which is why 89 it's 39%-106% slower. because he was interested in fast crypt(3) and 90 password-cracking applications, he also used the same ideas to 91 speed up the key-setting routines with impressive results. 92 (at some point i may do the same in my package). he also implements 93 the rest of the mit des library. 94 (code from eay@psych.psy.uq.oz.au via comp.sources.misc) 95 96fast crypt(3) package from denmark: 97 the des routine here is buried inside a loop to do the 98 crypt function and i didn't feel like ripping it out and measuring 99 performance. his code takes 26 sparc instructions to compute one 100 des iteration; above, Quick (64k) takes 21 and Small (2k) takes 37. 101 he claims to use 280k of tables but the iteration calculation seems 102 to use only 128k. his tables and code are machine independent. 103 (code from glad@daimi.aau.dk via alt.sources or comp.sources.misc) 104 105swedish reimplementation of Kerberos des library 106 108us per encryption (uses 34k worth of tables) 107 134us to set a new key (uses 32k of key tables to get this speed!) 108 the tables used seem to be machine-independent; 109 he seems to have included a lot of special case code 110 so that, e.g., `long' loads can be used instead of 4 `char' loads 111 when the machine's architecture allows it. 112 (code obtained from chalmers.se:pub/des) 113 114crack 3.3c package from england: 115 as in crypt above, the des routine is buried in a loop. it's 116 also very modified for crypt. his iteration code uses 16k 117 of tables and appears to be slow. 118 (code obtained from aem@aber.ac.uk via alt.sources or comp.sources.misc) 119 120``highly optimized'' and tweaked Kerberos/Athena code (byte-order dependent): 121 165us per encryption (uses 6k worth of tables) 122 478us to set a new key (uses <1k of key tables) 123 so despite the comments in this code, it was possible to get 124 faster code AND smaller tables, as well as making the tables 125 machine-independent. 126 (code obtained from prep.ai.mit.edu) 127 128UC Berkeley code (depends on machine-endedness): 129 226us per encryption 13010848us to set a new key 131 table sizes are unclear, but they don't look very small 132 (code obtained from wuarchive.wustl.edu) 133 134 135motivation and history 136 137a while ago i wanted some des routines and the routines documented on sun's 138man pages either didn't exist or dumped core. i had heard of kerberos, 139and knew that it used des, so i figured i'd use its routines. but once 140i got it and looked at the code, it really set off a lot of pet peeves - 141it was too convoluted, the code had been written without taking 142advantage of the regular structure of operations such as IP, E, and FP 143(i.e. the author didn't sit down and think before coding), 144it was excessively slow, the author had attempted to clarify the code 145by adding MORE statements to make the data movement more `consistent' 146instead of simplifying his implementation and cutting down on all data 147movement (in particular, his use of L1, R1, L2, R2), and it was full of 148idiotic `tweaks' for particular machines which failed to deliver significant 149speedups but which did obfuscate everything. so i took the test data 150from his verification program and rewrote everything else. 151 152a while later i ran across the great crypt(3) package mentioned above. 153the fact that this guy was computing 2 sboxes per table lookup rather 154than one (and using a MUCH larger table in the process) emboldened me to 155do the same - it was a trivial change from which i had been scared away 156by the larger table size. in his case he didn't realize you don't need to keep 157the working data in TWO forms, one for easy use of half the sboxes in 158indexing, the other for easy use of the other half; instead you can keep 159it in the form for the first half and use a simple rotate to get the other 160half. this means i have (almost) half the data manipulation and half 161the table size. in fairness though he might be encoding something particular 162to crypt(3) in his tables - i didn't check. 163 164i'm glad that i implemented it the way i did, because this C version is 165portable (the ifdef's are performance enhancements) and it is faster 166than versions hand-written in assembly for the sparc! 167 168 169porting notes 170 171one thing i did not want to do was write an enormous mess 172which depended on endedness and other machine quirks, 173and which necessarily produced different code and different lookup tables 174for different machines. see the kerberos code for an example 175of what i didn't want to do; all their endedness-specific `optimizations' 176obfuscate the code and in the end were slower than a simpler machine 177independent approach. however, there are always some portability 178considerations of some kind, and i have included some options 179for varying numbers of register variables. 180perhaps some will still regard the result as a mess! 181 1821) i assume everything is byte addressable, although i don't actually 183 depend on the byte order, and that bytes are 8 bits. 184 i assume word pointers can be freely cast to and from char pointers. 185 note that 99% of C programs make these assumptions. 186 i always use unsigned char's if the high bit could be set. 1872) the typedef `word' means a 32 bit unsigned integral type. 188 if `unsigned long' is not 32 bits, change the typedef in desCore.h. 189 i assume sizeof(word) == 4 EVERYWHERE. 190 191the (worst-case) cost of my NOT doing endedness-specific optimizations 192in the data loading and storing code surrounding the key iterations 193is less than 12%. also, there is the added benefit that 194the input and output work areas do not need to be word-aligned. 195 196 197OPTIONAL performance optimizations 198 1991) you should define one of `i386,' `vax,' `mc68000,' or `sparc,' 200 whichever one is closest to the capabilities of your machine. 201 see the start of desCode.h to see exactly what this selection implies. 202 note that if you select the wrong one, the des code will still work; 203 these are just performance tweaks. 2042) for those with functional `asm' keywords: you should change the 205 ROR and ROL macros to use machine rotate instructions if you have them. 206 this will save 2 instructions and a temporary per use, 207 or about 32 to 40 instructions per en/decryption. 208 note that gcc is smart enough to translate the ROL/R macros into 209 machine rotates! 210 211these optimizations are all rather persnickety, yet with them you should 212be able to get performance equal to assembly-coding, except that: 2131) with the lack of a bit rotate operator in C, rotates have to be synthesized 214 from shifts. so access to `asm' will speed things up if your machine 215 has rotates, as explained above in (3) (not necessary if you use gcc). 2162) if your machine has less than 12 32-bit registers i doubt your compiler will 217 generate good code. 218 `i386' tries to configure the code for a 386 by only declaring 3 registers 219 (it appears that gcc can use ebx, esi and edi to hold register variables). 220 however, if you like assembly coding, the 386 does have 7 32-bit registers, 221 and if you use ALL of them, use `scaled by 8' address modes with displacement 222 and other tricks, you can get reasonable routines for DesQuickCore... with 223 about 250 instructions apiece. For DesSmall... it will help to rearrange 224 des_keymap, i.e., now the sbox # is the high part of the index and 225 the 6 bits of data is the low part; it helps to exchange these. 226 since i have no way to conveniently test it i have not provided my 227 shoehorned 386 version. note that with this release of desCore, gcc is able 228 to put everything in registers(!), and generate about 370 instructions apiece 229 for the DesQuickCore... routines! 230 231coding notes 232 233the en/decryption routines each use 6 necessary register variables, 234with 4 being actively used at once during the inner iterations. 235if you don't have 4 register variables get a new machine. 236up to 8 more registers are used to hold constants in some configurations. 237 238i assume that the use of a constant is more expensive than using a register: 239a) additionally, i have tried to put the larger constants in registers. 240 registering priority was by the following: 241 anything more than 12 bits (bad for RISC and CISC) 242 greater than 127 in value (can't use movq or byte immediate on CISC) 243 9-127 (may not be able to use CISC shift immediate or add/sub quick), 244 1-8 were never registered, being the cheapest constants. 245b) the compiler may be too stupid to realize table and table+256 should 246 be assigned to different constant registers and instead repetitively 247 do the arithmetic, so i assign these to explicit `m' register variables 248 when possible and helpful. 249 250i assume that indexing is cheaper or equivalent to auto increment/decrement, 251where the index is 7 bits unsigned or smaller. 252this assumption is reversed for 68k and vax. 253 254i assume that addresses can be cheaply formed from two registers, 255or from a register and a small constant. 256for the 68000, the `two registers and small offset' form is used sparingly. 257all index scaling is done explicitly - no hidden shifts by log2(sizeof). 258 259the code is written so that even a dumb compiler 260should never need more than one hidden temporary, 261increasing the chance that everything will fit in the registers. 262KEEP THIS MORE SUBTLE POINT IN MIND IF YOU REWRITE ANYTHING. 263(actually, there are some code fragments now which do require two temps, 264but fixing it would either break the structure of the macros or 265require declaring another temporary). 266 267 268special efficient data format 269 270bits are manipulated in this arrangement most of the time (S7 S5 S3 S1): 271 003130292827xxxx242322212019xxxx161514131211xxxx080706050403xxxx 272(the x bits are still there, i'm just emphasizing where the S boxes are). 273bits are rotated left 4 when computing S6 S4 S2 S0: 274 282726252423xxxx201918171615xxxx121110090807xxxx040302010031xxxx 275the rightmost two bits are usually cleared so the lower byte can be used 276as an index into an sbox mapping table. the next two x'd bits are set 277to various values to access different parts of the tables. 278 279 280how to use the routines 281 282datatypes: 283 pointer to 8 byte area of type DesData 284 used to hold keys and input/output blocks to des. 285 286 pointer to 128 byte area of type DesKeys 287 used to hold full 768-bit key. 288 must be long-aligned. 289 290DesQuickInit() 291 call this before using any other routine with `Quick' in its name. 292 it generates the special 64k table these routines need. 293DesQuickDone() 294 frees this table 295 296DesMethod(m, k) 297 m points to a 128byte block, k points to an 8 byte des key 298 which must have odd parity (or -1 is returned) and which must 299 not be a (semi-)weak key (or -2 is returned). 300 normally DesMethod() returns 0. 301 m is filled in from k so that when one of the routines below 302 is called with m, the routine will act like standard des 303 en/decryption with the key k. if you use DesMethod, 304 you supply a standard 56bit key; however, if you fill in 305 m yourself, you will get a 768bit key - but then it won't 306 be standard. it's 768bits not 1024 because the least significant 307 two bits of each byte are not used. note that these two bits 308 will be set to magic constants which speed up the encryption/decryption 309 on some machines. and yes, each byte controls 310 a specific sbox during a specific iteration. 311 you really shouldn't use the 768bit format directly; i should 312 provide a routine that converts 128 6-bit bytes (specified in 313 S-box mapping order or something) into the right format for you. 314 this would entail some byte concatenation and rotation. 315 316Des{Small|Quick}{Fips|Core}{Encrypt|Decrypt}(d, m, s) 317 performs des on the 8 bytes at s into the 8 bytes at d. (d,s: char *). 318 uses m as a 768bit key as explained above. 319 the Encrypt|Decrypt choice is obvious. 320 Fips|Core determines whether a completely standard FIPS initial 321 and final permutation is done; if not, then the data is loaded 322 and stored in a nonstandard bit order (FIPS w/o IP/FP). 323 Fips slows down Quick by 10%, Small by 9%. 324 Small|Quick determines whether you use the normal routine 325 or the crazy quick one which gobbles up 64k more of memory. 326 Small is 50% slower then Quick, but Quick needs 32 times as much 327 memory. Quick is included for programs that do nothing but DES, 328 e.g., encryption filters, etc. 329 330 331Getting it to compile on your machine 332 333there are no machine-dependencies in the code (see porting), 334except perhaps the `now()' macro in desTest.c. 335ALL generated tables are machine independent. 336you should edit the Makefile with the appropriate optimization flags 337for your compiler (MAX optimization). 338 339 340Speeding up kerberos (and/or its des library) 341 342note that i have included a kerberos-compatible interface in desUtil.c 343through the functions des_key_sched() and des_ecb_encrypt(). 344to use these with kerberos or kerberos-compatible code put desCore.a 345ahead of the kerberos-compatible library on your linker's command line. 346you should not need to #include desCore.h; just include the header 347file provided with the kerberos library. 348 349Other uses 350 351the macros in desCode.h would be very useful for putting inline des 352functions in more complicated encryption routines. 353
