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A comment on Announcing the first SHA-1 collision. Parent comment

Re:Announcing the first SHA-1 collision by lisper on Thursday February 23, 2017 @02:21PM (#13716855)
It's instructive to diff the hexdumps of the two files. It's surprisingly small.
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Re:Announcing the first SHA-1 collision by susam on Friday February 24, 2017 @01:56AM (#13721633)
It is small indeed.

    $ diff -u <(xxd -g1 shattered-1.pdf) <(xxd -g1 shattered-2.pdf)
    --- /dev/fd/63	2017-02-24 12:25:17.311939732 +0530
    +++ /dev/fd/62	2017-02-24 12:25:17.311939732 +0530
    @@ -10,14 +10,14 @@
     0000090: 72 65 61 6d 0a ff d8 ff fe 00 24 53 48 41 2d 31  ream......$SHA-1
     00000a0: 20 69 73 20 64 65 61 64 21 21 21 21 21 85 2f ec   is dead!!!!!./.
     00000b0: 09 23 39 75 9c 39 b1 a1 c6 3c 4c 97 e1 ff fe 01  .#9u.9...<L.....
    -00000c0: 73 46 dc 91 66 b6 7e 11 8f 02 9a b6 21 b2 56 0f  sF..f.~.....!.V.
    -00000d0: f9 ca 67 cc a8 c7 f8 5b a8 4c 79 03 0c 2b 3d e2  ..g....[.Ly..+=.
    -00000e0: 18 f8 6d b3 a9 09 01 d5 df 45 c1 4f 26 fe df b3  ..m......E.O&...
    -00000f0: dc 38 e9 6a c2 2f e7 bd 72 8f 0e 45 bc e0 46 d2  .8.j./..r..E..F.
    -0000100: 3c 57 0f eb 14 13 98 bb 55 2e f5 a0 a8 2b e3 31  <W......U....+.1
    -0000110: fe a4 80 37 b8 b5 d7 1f 0e 33 2e df 93 ac 35 00  ...7.....3....5.
    -0000120: eb 4d dc 0d ec c1 a8 64 79 0c 78 2c 76 21 56 60  .M.....dy.x,v!V`
    -0000130: dd 30 97 91 d0 6b d0 af 3f 98 cd a4 bc 46 29 b1  .0...k..?....F).
    +00000c0: 7f 46 dc 93 a6 b6 7e 01 3b 02 9a aa 1d b2 56 0b  .F....~.;.....V.
    +00000d0: 45 ca 67 d6 88 c7 f8 4b 8c 4c 79 1f e0 2b 3d f6  E.g....K.Ly..+=.
    +00000e0: 14 f8 6d b1 69 09 01 c5 6b 45 c1 53 0a fe df b7  ..m.i...kE.S....
    +00000f0: 60 38 e9 72 72 2f e7 ad 72 8f 0e 49 04 e0 46 c2  `8.rr/..r..I..F.
    +0000100: 30 57 0f e9 d4 13 98 ab e1 2e f5 bc 94 2b e3 35  0W...........+.5
    +0000110: 42 a4 80 2d 98 b5 d7 0f 2a 33 2e c3 7f ac 35 14  B..-....*3....5.
    +0000120: e7 4d dc 0f 2c c1 a8 74 cd 0c 78 30 5a 21 56 64  .M..,..t..x0Z!Vd
    +0000130: 61 30 97 89 60 6b d0 bf 3f 98 cd a8 04 46 29 a1  a0..`k..?....F).
     0000140: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
     0000150: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
     0000160: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
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Re:Announcing the first SHA-1 collision by nneonneo on Thursday February 23, 2017 @02:26PM (#13716893)
The differences are confined to two SHA-1 input blocks of 64 bytes each. The first block introduces a carefully-crafted set of bit differences in the intermediate hash value (IHV), which are then eliminated in the second block. After the IHVs synchronize, all future blocks can be identical because SHA-1 can be trivially length-extended.
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