diff options
Diffstat (limited to 'third_party/heimdal/lib/hcrypto/DESperate.txt')
| -rw-r--r-- | third_party/heimdal/lib/hcrypto/DESperate.txt | 108 |
1 files changed, 108 insertions, 0 deletions
diff --git a/third_party/heimdal/lib/hcrypto/DESperate.txt b/third_party/heimdal/lib/hcrypto/DESperate.txt new file mode 100644 index 00000000000..3d793e9d879 --- /dev/null +++ b/third_party/heimdal/lib/hcrypto/DESperate.txt @@ -0,0 +1,108 @@ +The hunt for getting a DES with plain BSD license w/o advertisement clause +========================================================================== + +$Id$ + +This all feels very silly given that DES is about 30 years old and now +is deprecated. + +Helpful documents on the way: + +Schider's crypto wasn't that useful since it only told how to do DES, +not how to do des fast or how to not use DES. I find this to be a +common thread in the book, it explain each tool in great detail, but +not its limitations. + +Dag Arne Osvik: Efficient Implementation of the Data Encryption Standard + +Some threads on sci.crypto was also useful. + +PC1 transformations +=================== + + +Getting the PC1 bit mangling working was hard, I never got it to work. + +Printning out the bit usage made me realize a lookup table could be +used since only 12 bits are used from the first half and 16 from the +second. + +01110000 01110000 01110000 01110000 01111000 01111000 01111000 01111000 +00001111 00001111 00001111 00001111 00000111 00000111 00000111 00000111 + +The pattern is getting more obvious if it's printed out where the bits +are coming from. + + 8 16 24 - - - - - + 7 15 23 - - - - - + 6 14 22 - - - - - + 5 13 21 - - - - - + 4 12 20 28 - - - - + 3 11 19 27 - - - - + 2 10 18 26 - - - - + 1 9 17 25 - - - - + + - - - 60 56 48 40 - + - - - 59 55 47 39 - + - - - 58 54 46 38 - + - - - 57 53 45 37 - + - - - - 52 44 36 - + - - - - 51 43 35 - + - - - - 50 42 34 - + - - - - 49 41 33 - + +Only 3 bits-table is needed for the first half and 4 bits for the +second half because they are on diffrent shift offsets. + +So to get the bitpattern bit-pattern + +gen_pattern("pc1_c_3", 7, [ 5, 13, 21 ], 0, 0x1000000); +gen_pattern("pc1_c_4", 15, [ 1, 9, 17, 25 ], 0, 0x1000000); +gen_pattern("pc1_d_3", 7, [ 49, 41, 33 ], 32, 0x1000000); +gen_pattern("pc1_d_4", 15, [ 57, 53, 45, 37 ], 32, 0x1000000); + +PC2 transformations +=================== + +PC2 is also a table lookup, since it's a 24 bit field, I use 4 6-bit +lookup tables. Printing the reverse of the PC2 table reveal that some +of the bits are not used, namely (9, 18, 22, 25) from c and (7, 10, +15, 26) from d. + +pc2 from c +---------- + + 5 24 7 16 6 10 20 +18 - 12 3 15 23 1 + 9 19 2 - 14 22 11 + - 13 4 - 17 21 8 + +pc2 from d +---------- + +51 35 31 52 39 45 - +50 32 - 43 36 29 48 + - 41 38 47 33 40 42 +49 37 30 46 - 34 44 + +So we generate tables for that too. + +gen_pattern("pc2_c_1", 63, [ 5, 24, 7, 16, 6, 10 ], 0, 0x800000); +gen_pattern("pc2_c_2", 63, [ 20, 18, 12, 3, 15, 23 ], 0, 0x800000); +gen_pattern("pc2_c_3", 63, [ 1, 9, 19, 2, 14, 22 ], 0, 0x800000); +gen_pattern("pc2_c_4", 63, [ 11, 13, 4, 17, 21, 8 ], 0, 0x800000); + +gen_pattern("pc2_d_1", 63, [ 51, 35, 31, 52, 39, 45 ], 28, 0x800000); +gen_pattern("pc2_d_2", 63, [ 50, 32, 43, 36, 29, 48 ], 28, 0x800000); +gen_pattern("pc2_d_3", 63, [ 41, 38, 47, 33, 40, 42 ], 28, 0x800000); +gen_pattern("pc2_d_4", 63, [ 49, 37, 30, 46, 34, 44 ], 28, 0x800000); + + +SBOX transformations +==================== + +The SBOX transformations are 6 bit to 4 bit transformations. + +Here I grew tired and used Richard Outerbridge SBOXes. Thank you +Richard. + |