Update the Example in the crypto/ecdsa package for signing
and verifying signatures to use these new functions.
This also changes (*PrivateKey).Sign to use
x/crypto/cryptobyte/asn1 instead of encoding/asn1
to marshal the signature.
Fixes#20544
Change-Id: I3423cfc4d7f9e1748fbed5a631438c8a3b280df4
Reviewed-on: https://go-review.googlesource.com/c/go/+/217940
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Each URL was manually verified to ensure it did not serve up incorrect
content.
Change-Id: I4dc846227af95a73ee9a3074d0c379ff0fa955df
Reviewed-on: https://go-review.googlesource.com/115798
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
The optimised P-256 includes a CombinedMult function, which doesn't do
dual-scalar multiplication, but does avoid an affine conversion for
ECDSA verification.
However, it currently uses an assembly point addition function that
doesn't handle exceptional cases.
Fixes#20215.
Change-Id: I4ba2ca1a546d883364a9bb6bf0bdbc7f7b44c94a
Reviewed-on: https://go-review.googlesource.com/42611
Run-TryBot: Adam Langley <agl@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>
The existing implementation used a pure go implementation, leading to slow
cryptographic performance.
Implemented mulWW, subVV, mulAddVWW, addMulVVW, and bitLen for
ppc64{le}.
Implemented divWW for ppc64le only, as the DIVDEU instruction is only
available on Power8 or newer.
benchcmp output:
benchmark old ns/op new ns/op delta
BenchmarkSignP384 28934360 10877330 -62.41%
BenchmarkRSA2048Decrypt 41261033 5139930 -87.54%
BenchmarkRSA2048Sign 45231300 7610985 -83.17%
Benchmark3PrimeRSA2048Decrypt 20487300 2481408 -87.89%
Fixes#16621
Change-Id: If8b68963bb49909bde832f2bda08a3791c4f5b7a
Reviewed-on: https://go-review.googlesource.com/26951
Run-TryBot: Michael Munday <munday@ca.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Munday <munday@ca.ibm.com>
The fact that crypto/ecdsa.Verify didn't reject negative inputs was a
mistake on my part: I had unsigned numbers on the brain. However, it
doesn't generally cause problems. (ModInverse results in zero, which
results in x being zero, which is rejected.)
The amd64 P-256 code will crash when given a large, negative input.
This fixes both crypto/ecdsa to reject these values and also the P-256
code to ignore the sign of inputs.
Change-Id: I6370ed7ca8125e53225866f55b616a4022b818f8
Reviewed-on: https://go-review.googlesource.com/22093
Run-TryBot: Adam Langley <agl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This is based on the implementation used in OpenSSL, from a
submission by Shay Gueron and myself. Besides using assembly,
this implementation employs several optimizations described in:
S.Gueron and V.Krasnov, "Fast prime field elliptic-curve
cryptography with 256-bit primes"
In addition a new and improved modular inverse modulo N is
implemented here.
The performance measured on a Haswell based Macbook Pro shows 21X
speedup for the sign and 9X for the verify operations.
The operation BaseMult is 30X faster (and the Diffie-Hellman/ECDSA
key generation that use it are sped up as well).
The adaptation to Go with the help of Filippo Valsorda
Updated the submission for faster verify/ecdh, fixed some asm syntax
and API problems and added benchmarks.
Change-Id: I86a33636747d5c92f15e0c8344caa2e7e07e0028
Reviewed-on: https://go-review.googlesource.com/8968
Run-TryBot: Adam Langley <agl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>
Could go in 1.5, although not critical.
See also #12107
Change-Id: I7f1608b58581d21df4db58f0db654fef79e33a90
Reviewed-on: https://go-review.googlesource.com/13481
Reviewed-by: Dave Cheney <dave@cheney.net>
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>
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.
--
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"
Fixes#9452
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.
Change-Id: Ie7e04057a3a26e6becb80e845ecb5004bb482745
Reviewed-on: https://go-review.googlesource.com/2422
Reviewed-by: Adam Langley <agl@golang.org>
