2013-12-20 16:37:05 +00:00
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>>> Flow 1 (client to server)
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2016-10-12 18:53:35 +01:00
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00000000 16 03 01 00 a7 01 00 00 a3 03 03 27 01 f3 21 98 |...........'..!.|
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00000010 ff 55 7f 78 32 44 b7 9d 88 6b 82 43 26 52 00 74 |.U.x2D...k.C&R.t|
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00000020 fb 05 ca be 23 1f d0 18 1f 74 c2 00 00 38 c0 2c |....#....t...8.,|
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2016-10-11 18:08:57 +01:00
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00000030 c0 30 00 9f cc a9 cc a8 cc aa c0 2b c0 2f 00 9e |.0.........+./..|
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00000040 c0 24 c0 28 00 6b c0 23 c0 27 00 67 c0 0a c0 14 |.$.(.k.#.'.g....|
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00000050 00 39 c0 09 c0 13 00 33 00 9d 00 9c 00 3d 00 3c |.9.....3.....=.<|
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00000060 00 35 00 2f 00 ff 01 00 00 42 00 0b 00 04 03 00 |.5./.....B......|
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00000070 01 02 00 0a 00 0a 00 08 00 1d 00 17 00 19 00 18 |................|
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00000080 00 0d 00 20 00 1e 06 01 06 02 06 03 05 01 05 02 |... ............|
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00000090 05 03 04 01 04 02 04 03 03 01 03 02 03 03 02 01 |................|
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000000a0 02 02 02 03 00 16 00 00 00 17 00 00 |............|
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2013-12-20 16:37:05 +00:00
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>>> Flow 2 (server to client)
|
crypto/ecdsa: make Sign safe with broken entropy sources
ECDSA is unsafe to use if an entropy source produces predictable
output for the ephemeral nonces. E.g., [Nguyen]. A simple
countermeasure is to hash the secret key, the message, and
entropy together to seed a CSPRNG, from which the ephemeral key
is derived.
Fixes #9452
--
This is a minimalist (in terms of patch size) solution, though
not the most parsimonious in its use of primitives:
- csprng_key = ChopMD-256(SHA2-512(priv.D||entropy||hash))
- reader = AES-256-CTR(k=csprng_key)
This, however, provides at most 128-bit collision-resistance,
so that Adv will have a term related to the number of messages
signed that is significantly worse than plain ECDSA. This does
not seem to be of any practical importance.
ChopMD-256(SHA2-512(x)) is used, rather than SHA2-256(x), for
two sets of reasons:
*Practical:* SHA2-512 has a larger state and 16 more rounds; it
is likely non-generically stronger than SHA2-256. And, AFAIK,
cryptanalysis backs this up. (E.g., [Biryukov] gives a
distinguisher on 47-round SHA2-256 with cost < 2^85.) This is
well below a reasonable security-strength target.
*Theoretical:* [Coron] and [Chang] show that Chop-MD(F(x)) is
indifferentiable from a random oracle for slightly beyond the
birthday barrier. It seems likely that this makes a generic
security proof that this construction remains UF-CMA is
possible in the indifferentiability framework.
--
Many thanks to Payman Mohassel for reviewing this construction;
any mistakes are mine, however. And, as he notes, reusing the
private key in this way means that the generic-group (non-RO)
proof of ECDSA's security given in [Brown] no longer directly
applies.
--
[Brown]: http://www.cacr.math.uwaterloo.ca/techreports/2000/corr2000-54.ps
"Brown. The exact security of ECDSA. 2000"
[Coron]: https://www.cs.nyu.edu/~puniya/papers/merkle.pdf
"Coron et al. Merkle-Damgard revisited. 2005"
[Chang]: https://www.iacr.org/archive/fse2008/50860436/50860436.pdf
"Chang and Nandi. Improved indifferentiability security analysis
of chopMD hash function. 2008"
[Biryukov]: http://www.iacr.org/archive/asiacrypt2011/70730269/70730269.pdf
"Biryukov et al. Second-order differential collisions for reduced
SHA-256. 2011"
[Nguyen]: ftp://ftp.di.ens.fr/pub/users/pnguyen/PubECDSA.ps
"Nguyen and Shparlinski. The insecurity of the elliptic curve
digital signature algorithm with partially known nonces. 2003"
New tests:
TestNonceSafety: Check that signatures are safe even with a
broken entropy source.
TestINDCCA: Check that signatures remain non-deterministic
with a functional entropy source.
Updated "golden" KATs in crypto/tls/testdata that use ECDSA suites.
Change-Id: I55337a2fbec2e42a36ce719bd2184793682d678a
Reviewed-on: https://go-review.googlesource.com/3340
Reviewed-by: Adam Langley <agl@golang.org>
2015-01-27 07:00:21 +00:00
|
|
|
00000000 16 03 03 00 31 02 00 00 2d 03 03 00 00 00 00 00 |....1...-.......|
|
2013-12-20 16:37:05 +00:00
|
|
|
00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|
crypto/ecdsa: make Sign safe with broken entropy sources
ECDSA is unsafe to use if an entropy source produces predictable
output for the ephemeral nonces. E.g., [Nguyen]. A simple
countermeasure is to hash the secret key, the message, and
entropy together to seed a CSPRNG, from which the ephemeral key
is derived.
Fixes #9452
--
This is a minimalist (in terms of patch size) solution, though
not the most parsimonious in its use of primitives:
- csprng_key = ChopMD-256(SHA2-512(priv.D||entropy||hash))
- reader = AES-256-CTR(k=csprng_key)
This, however, provides at most 128-bit collision-resistance,
so that Adv will have a term related to the number of messages
signed that is significantly worse than plain ECDSA. This does
not seem to be of any practical importance.
ChopMD-256(SHA2-512(x)) is used, rather than SHA2-256(x), for
two sets of reasons:
*Practical:* SHA2-512 has a larger state and 16 more rounds; it
is likely non-generically stronger than SHA2-256. And, AFAIK,
cryptanalysis backs this up. (E.g., [Biryukov] gives a
distinguisher on 47-round SHA2-256 with cost < 2^85.) This is
well below a reasonable security-strength target.
*Theoretical:* [Coron] and [Chang] show that Chop-MD(F(x)) is
indifferentiable from a random oracle for slightly beyond the
birthday barrier. It seems likely that this makes a generic
security proof that this construction remains UF-CMA is
possible in the indifferentiability framework.
--
Many thanks to Payman Mohassel for reviewing this construction;
any mistakes are mine, however. And, as he notes, reusing the
private key in this way means that the generic-group (non-RO)
proof of ECDSA's security given in [Brown] no longer directly
applies.
--
[Brown]: http://www.cacr.math.uwaterloo.ca/techreports/2000/corr2000-54.ps
"Brown. The exact security of ECDSA. 2000"
[Coron]: https://www.cs.nyu.edu/~puniya/papers/merkle.pdf
"Coron et al. Merkle-Damgard revisited. 2005"
[Chang]: https://www.iacr.org/archive/fse2008/50860436/50860436.pdf
"Chang and Nandi. Improved indifferentiability security analysis
of chopMD hash function. 2008"
[Biryukov]: http://www.iacr.org/archive/asiacrypt2011/70730269/70730269.pdf
"Biryukov et al. Second-order differential collisions for reduced
SHA-256. 2011"
[Nguyen]: ftp://ftp.di.ens.fr/pub/users/pnguyen/PubECDSA.ps
"Nguyen and Shparlinski. The insecurity of the elliptic curve
digital signature algorithm with partially known nonces. 2003"
New tests:
TestNonceSafety: Check that signatures are safe even with a
broken entropy source.
TestINDCCA: Check that signatures remain non-deterministic
with a functional entropy source.
Updated "golden" KATs in crypto/tls/testdata that use ECDSA suites.
Change-Id: I55337a2fbec2e42a36ce719bd2184793682d678a
Reviewed-on: https://go-review.googlesource.com/3340
Reviewed-by: Adam Langley <agl@golang.org>
2015-01-27 07:00:21 +00:00
|
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00000020 00 00 00 00 00 00 00 00 00 00 00 00 c0 0a 00 00 |................|
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00000030 05 ff 01 00 01 00 16 03 03 02 0e 0b 00 02 0a 00 |................|
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00000040 02 07 00 02 04 30 82 02 00 30 82 01 62 02 09 00 |.....0...0..b...|
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00000050 b8 bf 2d 47 a0 d2 eb f4 30 09 06 07 2a 86 48 ce |..-G....0...*.H.|
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00000060 3d 04 01 30 45 31 0b 30 09 06 03 55 04 06 13 02 |=..0E1.0...U....|
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00000070 41 55 31 13 30 11 06 03 55 04 08 13 0a 53 6f 6d |AU1.0...U....Som|
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00000080 65 2d 53 74 61 74 65 31 21 30 1f 06 03 55 04 0a |e-State1!0...U..|
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00000090 13 18 49 6e 74 65 72 6e 65 74 20 57 69 64 67 69 |..Internet Widgi|
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000000a0 74 73 20 50 74 79 20 4c 74 64 30 1e 17 0d 31 32 |ts Pty Ltd0...12|
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000000b0 31 31 32 32 31 35 30 36 33 32 5a 17 0d 32 32 31 |1122150632Z..221|
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000000c0 31 32 30 31 35 30 36 33 32 5a 30 45 31 0b 30 09 |120150632Z0E1.0.|
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000000d0 06 03 55 04 06 13 02 41 55 31 13 30 11 06 03 55 |..U....AU1.0...U|
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000000e0 04 08 13 0a 53 6f 6d 65 2d 53 74 61 74 65 31 21 |....Some-State1!|
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000000f0 30 1f 06 03 55 04 0a 13 18 49 6e 74 65 72 6e 65 |0...U....Interne|
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00000100 74 20 57 69 64 67 69 74 73 20 50 74 79 20 4c 74 |t Widgits Pty Lt|
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00000110 64 30 81 9b 30 10 06 07 2a 86 48 ce 3d 02 01 06 |d0..0...*.H.=...|
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00000120 05 2b 81 04 00 23 03 81 86 00 04 00 c4 a1 ed be |.+...#..........|
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00000130 98 f9 0b 48 73 36 7e c3 16 56 11 22 f2 3d 53 c3 |...Hs6~..V.".=S.|
|
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00000140 3b 4d 21 3d cd 6b 75 e6 f6 b0 dc 9a df 26 c1 bc |;M!=.ku......&..|
|
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00000150 b2 87 f0 72 32 7c b3 64 2f 1c 90 bc ea 68 23 10 |...r2|.d/....h#.|
|
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00000160 7e fe e3 25 c0 48 3a 69 e0 28 6d d3 37 00 ef 04 |~..%.H:i.(m.7...|
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00000170 62 dd 0d a0 9c 70 62 83 d8 81 d3 64 31 aa 9e 97 |b....pb....d1...|
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00000180 31 bd 96 b0 68 c0 9b 23 de 76 64 3f 1a 5c 7f e9 |1...h..#.vd?.\..|
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00000190 12 0e 58 58 b6 5f 70 dd 9b d8 ea d5 d7 f5 d5 cc |..XX._p.........|
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000001a0 b9 b6 9f 30 66 5b 66 9a 20 e2 27 e5 bf fe 3b 30 |...0f[f. .'...;0|
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000001b0 09 06 07 2a 86 48 ce 3d 04 01 03 81 8c 00 30 81 |...*.H.=......0.|
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000001c0 88 02 42 01 88 a2 4f eb e2 45 c5 48 7d 1b ac f5 |..B...O..E.H}...|
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000001d0 ed 98 9d ae 47 70 c0 5e 1b b6 2f bd f1 b6 4d b7 |....Gp.^../...M.|
|
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000001e0 61 40 d3 11 a2 ce ee 0b 7e 92 7e ff 76 9d c3 3b |a@......~.~.v..;|
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000001f0 7e a5 3f ce fa 10 e2 59 ec 47 2d 7c ac da 4e 97 |~.?....Y.G-|..N.|
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00000200 0e 15 a0 6f d0 02 42 01 4d fc be 67 13 9c 2d 05 |...o..B.M..g..-.|
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00000210 0e bd 3f a3 8c 25 c1 33 13 83 0d 94 06 bb d4 37 |..?..%.3.......7|
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00000220 7a f6 ec 7a c9 86 2e dd d7 11 69 7f 85 7c 56 de |z..z......i..|V.|
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00000230 fb 31 78 2b e4 c7 78 0d ae cb be 9e 4e 36 24 31 |.1x+..x.....N6$1|
|
2016-10-11 23:08:35 +01:00
|
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00000240 7b 6a 0f 39 95 12 07 8f 2a 16 03 03 00 b7 0c 00 |{j.9....*.......|
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00000250 00 b3 03 00 1d 20 2f e5 7d a3 47 cd 62 43 15 28 |..... /.}.G.bC.(|
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00000260 da ac 5f bb 29 07 30 ff f6 84 af c4 cf c2 ed 90 |.._.).0.........|
|
2016-10-12 18:53:35 +01:00
|
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00000270 99 5f 58 cb 3b 74 05 03 00 8b 30 81 88 02 42 01 |._X.;t....0...B.|
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00000280 4f 30 aa d0 4d e5 61 db ba fc 95 15 52 ef 2a 41 |O0..M.a.....R.*A|
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00000290 b4 d6 59 ac 39 61 b6 38 08 1e 87 b3 ca 9b 49 d3 |..Y.9a.8......I.|
|
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000002a0 95 5a c5 29 84 cd 10 73 4a cc 09 df 1a b0 54 6d |.Z.)...sJ.....Tm|
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000002b0 b8 61 28 80 2e ec cf 95 9d 6f c3 d9 ed 80 53 63 |.a(......o....Sc|
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000002c0 d9 02 42 00 af 71 2f 91 80 ff a1 79 82 c7 d9 79 |..B..q/....y...y|
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000002d0 fa 12 a9 88 7b 93 47 be 6a dc 80 42 17 9d 85 7a |....{.G.j..B...z|
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000002e0 b8 1b fe 85 7f 5c 10 9c 9e 0e e1 71 a7 b0 12 02 |.....\.....q....|
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000002f0 e2 a4 79 c4 8d d8 02 09 01 9c 6f 7a 27 7c 1f f4 |..y.......oz'|..|
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00000300 38 46 59 46 94 16 03 03 00 04 0e 00 00 00 |8FYF..........|
|
2013-12-20 16:37:05 +00:00
|
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|
>>> Flow 3 (client to server)
|
2016-10-12 18:53:35 +01:00
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00000000 16 03 03 00 25 10 00 00 21 20 8c 80 e4 c7 bd d7 |....%...! ......|
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00000010 ea ea 42 f7 53 24 50 28 6a e9 f3 ff 4f 4a 28 22 |..B.S$P(j...OJ("|
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00000020 a2 95 09 fc f0 d9 3e fc cc 6e 14 03 03 00 01 01 |......>..n......|
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00000030 16 03 03 00 40 79 56 60 f5 45 e7 48 9e 97 1d 49 |....@yV`.E.H...I|
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00000040 de 59 dd b0 f0 0a d2 cc 10 f0 98 3c c2 d5 67 d6 |.Y.........<..g.|
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00000050 2c 18 2b 21 ae a3 2f ea 2d 0b ff fd e6 c2 73 25 |,.+!../.-.....s%|
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00000060 1c 01 3e 94 3a cc 1d 58 6b fb 7f 85 e4 50 ec 10 |..>.:..Xk....P..|
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00000070 b9 d7 71 cb be |..q..|
|
2013-12-20 16:37:05 +00:00
|
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>>> Flow 4 (server to client)
|
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00000000 14 03 03 00 01 01 16 03 03 00 40 00 00 00 00 00 |..........@.....|
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2016-10-12 18:53:35 +01:00
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00000010 00 00 00 00 00 00 00 00 00 00 00 83 5c 5c e3 c0 |............\\..|
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00000020 20 56 8c 92 4b 75 f0 30 bd 67 74 52 f1 af 9c 14 | V..Ku.0.gtR....|
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00000030 29 1e e4 b2 5b c0 2c e6 48 6f 94 42 7b 21 92 96 |)...[.,.Ho.B{!..|
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00000040 0a 83 ce 1c 91 36 95 8c 14 38 57 17 03 03 00 40 |.....6...8W....@|
|
2013-12-20 16:37:05 +00:00
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00000050 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|
2016-10-12 18:53:35 +01:00
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00000060 73 a4 40 cf ad 86 cc 05 9e 47 5f 83 50 ae 68 d5 |s.@......G_.P.h.|
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00000070 d1 6a a9 8c ba 74 fe c0 cc 4a 1a e3 b0 14 0d 31 |.j...t...J.....1|
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00000080 9f 06 54 e3 95 3a 89 6d 34 54 0c e4 b4 34 38 21 |..T..:.m4T...48!|
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2013-12-20 16:37:05 +00:00
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00000090 15 03 03 00 30 00 00 00 00 00 00 00 00 00 00 00 |....0...........|
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2016-10-12 18:53:35 +01:00
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000000a0 00 00 00 00 00 e6 dd b2 11 ab a7 34 61 00 d4 09 |...........4a...|
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000000b0 bc ea c1 5f c4 e2 52 60 63 96 f0 fd 44 4e f9 0e |..._..R`c...DN..|
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000000c0 af 32 99 e4 12 |.2...|
|
