mirror of git://sourceware.org/git/glibc.git
136 lines
4.5 KiB
Plaintext
136 lines
4.5 KiB
Plaintext
The following is the README for UFC-crypt, with those portions deleted
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that are known to be incorrect for the implementation used with the
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GNU C library.
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UFC-crypt: ultra fast 'crypt' implementation
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============================================
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@(#)README 2.27 11 Sep 1996
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Design goals/non goals:
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----------------------
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- Crypt implementation plugin compatible with crypt(3)/fcrypt.
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- High performance when used for password cracking.
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- Portable to most 32/64 bit machines.
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- Startup time/mixed salt performance not critical.
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Features of the implementation:
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------------------------------
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- On most machines, UFC-crypt runs 30-60 times faster than crypt(3) when
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invoked repeated times with the same salt and varying passwords.
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- With mostly constant salts, performance is about two to three times
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that of the default fcrypt implementation shipped with Alec
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Muffets 'Crack' password cracker. For instructions on how to
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plug UFC-crypt into 'Crack', see below.
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- With alternating salts, performance is only about twice
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that of crypt(3).
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- Requires 165 kb for tables.
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Author & licensing etc
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----------------------
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UFC-crypt is created by Michael Glad, email: glad@daimi.aau.dk, and has
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been donated to the Free Software Foundation, Inc. It is covered by the
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GNU library license version 2, see the file 'COPYING.LIB'.
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NOTES FOR USERS OUTSIDE THE US:
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------------------------------
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The US government limits the export of DES based software/hardware.
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This software is written in Aarhus, Denmark. It can therefore be retrieved
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from ftp sites outside the US without breaking US law. Please do not
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ftp it from american sites.
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Benchmark table:
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---------------
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The table shows how many operations per second UFC-crypt can
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do on various machines.
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|--------------|-------------------------------------------|
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|Machine | SUN* SUN* HP* DecStation HP |
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| | 3/50 ELC 9000/425e 3100 9000/720 |
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|--------------|-------------------------------------------|
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| Crypt(3)/sec | 4.6 30 15 25 57 |
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| Ufc/sec | 220 990 780 1015 3500 |
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|--------------|-------------------------------------------|
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| Speedup | 48 30 52 40 60 |
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|--------------|-------------------------------------------|
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*) Compiled using special assembly language support module.
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It seems as if performance is limited by CPU bus and data cache capacity.
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This also makes the benchmarks debatable compared to a real test with
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UFC-crypt wired into Crack. However, the table gives an outline of
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what can be expected.
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Optimizations:
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-------------
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Here are the optimizations used relative to an ordinary implementation
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such as the one said to be used in crypt(3).
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Major optimizations
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*******************
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- Keep data packed as bits in integer variables -- allows for
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fast permutations & parallel xor's in CPU hardware.
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- Let adjacent final & initial permutations collapse.
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- Keep working data in 'E expanded' format all the time.
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- Implement DES 'f' function mostly by table lookup
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- Calculate the above function on 12 bit basis rather than 6
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as would be the most natural.
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- Implement setup routines so that performance is limited by the DES
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inner loops only.
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- Instead of doing salting in the DES inner loops, modify the above tables
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each time a new salt is seen. According to the BSD crypt code this is
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ugly :-)
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Minor (dirty) optimizations
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***************************
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- combine iterations of DES inner loop so that DES only loops
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8 times. This saves a lot of variable swapping.
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- Implement key access by a walking pointer rather than coding
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as array indexing.
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- As described, the table based f function uses a 3 dimensional array:
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sb ['number of 12 bit segment']['12 bit index']['48 bit half index']
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Code the routine with 4 (one dimensional) vectors.
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- Design the internal data format & uglify the DES loops so that
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the compiler does not need to do bit shifts when indexing vectors.
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Revision history
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****************
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UFC patchlevel 0: base version; released to alt.sources on Sep 24 1991
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UFC patchlevel 1: patch released to alt.sources on Sep 27 1991.
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No longer rebuilds sb tables when seeing a new salt.
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UFC-crypt pl0: Essentially UFC pl 1. Released to comp.sources.misc
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on Oct 22 1991.
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UFC-crypt pl1: Released to comp.sources.misc in march 1992
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* setkey/encrypt routines added
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* added validation/benchmarking programs
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* reworked keyschedule setup code
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* memory demands reduced
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* 64 bit support added
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