Rewrite ec abstraction #17

omershlo · 2018-08-04T18:23:49Z

No description provided.

omershlo · 2018-08-04T18:29:51Z

I made major changes to EC traits. currently implemented only for secp256k1. Unit tests are needed as well as implementation for curve25519.
The major milestone so far is the generic traits ECScalar and ECPoint and the EC specific implementation for Secp256k1Scalar and Secp256k1Point. Any discussion and feedback at this level are welcome

omershlo · 2018-08-08T20:05:32Z

I changed the elliptic curves to be features. need to find a way to make the compilation of the crates optional such that we compile only the EC we need.

romanz · 2018-08-12T14:49:39Z

The build seems to be failing: https://travis-ci.com/KZen-networks/cryptography-utils/jobs/139499279#L694:

$ cargo +nightly check --all
    Checking cryptography-utils v0.1.0 (file:///home/roman/Code/KZen/cryptography-utils)                                                                                                                                                                                        
error[E0432]: unresolved import `FE`
  --> src/cryptographic_primitives/proofs/dlog_zk_protocol.rs:34:5
   |
34 | use FE;
   |     ^^ no `FE` in the root

error[E0432]: unresolved import `GE`
  --> src/cryptographic_primitives/proofs/dlog_zk_protocol.rs:35:5
   |
35 | use GE;
   |     ^^ no `GE` in the root

error[E0432]: unresolved import `PK`
  --> src/cryptographic_primitives/proofs/dlog_zk_protocol.rs:36:5
   |
36 | use PK;
   |     ^^ no `PK` in the root

error[E0432]: unresolved import `SK`
  --> src/cryptographic_primitives/proofs/dlog_zk_protocol.rs:37:5
   |
37 | use SK;
   |     ^^ no `SK` in the root

omershlo · 2018-08-12T14:52:27Z

@romanz this is because you must choose an elliptic curve feature for the build to be successful.

romanz · 2018-08-12T17:08:25Z

@omershlo Thanks! It should be fixed by a9d78ef.

romanz

Mostly style and naming-related comments; didn't review the cryptography-related changes.

romanz · 2018-08-12T17:40:32Z

Cargo.toml

@@ -8,9 +8,14 @@ authors = [
 [lib]
 crate-type = ["lib"]

+[features]
+#default = ["curve25519"]


Please remove the commented line - or set the default explicitly.

romanz · 2018-08-12T18:51:38Z

src/cryptographic_primitives/hashing/hash_sha512.rs

+
+        for value in big_ints {
+            let bytes: Vec<u8> = value.borrow().into();
+            digest.update(&bytes);


Can this be written as digest.update(&value.to_vec())?

If so - please change hash_sha256.rs as well.

@gbenattar ?

changed it. thanks!

romanz · 2018-08-12T18:53:23Z

src/cryptographic_primitives/proofs/dlog_zk_protocol.rs

+//#[cfg(feature="curvesecp256k1")]
+//use secp256k1instance::{SK,PK,GE,FE};
+//#[cfg(feature="curve25519-dalek")]
+//use curve25519instance::{SK,PK,GE,FE};


Please delete the commented code blocks (above and in the rest of the changed code).

romanz · 2018-08-12T19:04:01Z

src/elliptic/curves/curve25519.rs

+// Secp256k1 elliptic curve utility functions (se: https://en.bitcoin.it/wiki/Secp256k1).
+//
+// In Cryptography utilities, we need to manipulate low level elliptic curve members as Point
+// in order to perform operation on them. As the library secp256k1 expose only SecretKey and


secp256k1 -> curve25519

romanz · 2018-08-12T19:06:48Z

src/elliptic/curves/curve25519.rs

+
+    fn sub(&self, other: &SK) -> Curve25519Scalar {
+        Curve25519Scalar {
+            purpose: "mul",


mul -> sub

romanz · 2018-08-12T19:08:08Z

src/elliptic/curves/traits.rs

-
+// TODO: add a fn is_point
+pub trait ECPoint<PK, SK> {
+    fn new() -> Self;


Consider naming it generator() (instead of new()).

done. good idea!!

romanz · 2018-08-12T19:09:26Z

src/lib.rs

+#[cfg(feature = "curvesecp256k1")]
+mod secp256k1instance {
+
+    pub use elliptic::curves::secp256_k1::EC;


Consider removing the line (as "curve25519" doesn't export an EC type).

mortendahl

some comments, but didn't look too closely at the crypto parts -- is that a review priority as well? anything that's worth focusing specifically on?

mortendahl · 2018-08-29T11:56:00Z

src/cryptographic_primitives/commitments/pedersen_commitment.rs

+
+pub struct PedersenCommitment;
+
+impl Commitment<Secp256k1Point> for PedersenCommitment {


won't this fail when not using feature curvesecp256k1? maybe find a way to use conditional compilation to leave this code out in those cases

yes, the reason was that not every elliptic curve that is used for signing can be used for Pedersen commitment as well so when new elliptic curves are introduced we would add pedersen commitment based on them. But your point is solid. @gbenattar @romanz do you know of a way to support Pederesen with fixed elliptic curve while condition compilation on all other elliptic curve related stuff? this might come in useful in the future?

out of curiosity, what determines whether a curve can be used for commitment or not?

for conditional compilation you can simply annotate the impl with #[cfg(feature = "...")]

If the curve is prime order group or not. For example curve25519 is not.

I sprayed #[cfg(feature = "curvesecp256k1")] all over the place. It appears that we are using pedersen commitments in many places. @romanz @mortendahl @gbenattar maybe one of you have an idea on how to do this exclusion more elegant or at least how to minimize the times I use #[cfg(feature = "curvesecp256k1")]?

mortendahl · 2018-09-03T08:05:51Z

src/cryptographic_primitives/commitments/hash_commitment.rs

 pub struct HashCommitment;

 //TODO:  using the function with BigInt's as input instead of string's makes it impossible to commit to empty message or use empty randomness
-impl Commitment for HashCommitment {
+impl Commitment<BigInt> for HashCommitment {
    fn create_commitment_with_user_defined_randomness(


create_commitment_with_user_defined_randomness and create_commitment share almost the same code; let one use the other?

done. good catch.

mortendahl · 2018-09-03T08:06:47Z

src/cryptographic_primitives/commitments/pedersen_commitment.rs

+        mg.add_point(&rh.get_element())
+    }
+
+    fn create_commitment(message: &BigInt) -> (Secp256k1Point, BigInt) {


both methods again share almost the same code; let one use the other?

mortendahl · 2018-09-03T08:09:47Z

Cargo.toml

+[features]
+default = ["curvesecp256k1"]
+curvesecp256k1 = []
+curve25519 = []


couldn't get it to compile with this curve (blocked on serde errors)

@gbenattar probably some backward compatibility issue from your work on serialization?

The default one? Just to make sure, do a cargo update and also do a rustup update, they changed nightly recently.

@gbenattar not the default one, the build is failing for curve25519 because serde is not implemented for this.

mortendahl · 2018-09-03T08:18:24Z

src/cryptographic_primitives/hashing/hmac_sha512.rs

+*/
+use BigInt;
+
+use super::ring::{digest, hmac};


I think the extern crate ring is in the wrong place if super is needed here

completely right, moved it to lib.rs

mortendahl · 2018-09-03T08:59:22Z

src/cryptographic_primitives/proofs/sigma_dlog.rs

+            &generator_x,
+            &pk.get_x_coor_as_big_int(),
+        ]);
+        let challenge_fe: FE = ECScalar::from_big_int(&challenge);


some methods perhaps seem a bit more explicit in naming than typical rust code, eg from_big_int instead of simply from, get_element instead of element, and get_x_coor_as_big_int instead of x_coor

I changed the interface. my only problem is with get_element - I need to differentiate it from set_element so I cannot just change it to element

mortendahl · 2018-09-03T09:01:13Z

src/cryptographic_primitives/proofs/sigma_dlog.rs

+
+        let base_point: GE = ECPoint::new();
+        //let sk_challenge_response : FE = ECScalar::from_big_int(&proof.challenge_response);
+        let sk_challenge_response: FE = proof.challenge_response.clone();


no need to clone

mortendahl · 2018-09-03T09:05:50Z

src/cryptographic_primitives/proofs/sigma_valid_pedersen.rs

+use cryptographic_primitives::commitments::pedersen_commitment::PedersenCommitment;
+use cryptographic_primitives::commitments::traits::Commitment;
+
+use elliptic::curves::secp256_k1::Secp256k1Point;


conditional compilation to only be included when this curve is used?

mortendahl · 2018-09-03T09:09:45Z

src/cryptographic_primitives/proofs/sigma_valid_pedersen.rs

+        let lhs = z1g.add_point(&z2h.get_element());
+        let rhs = proof.a1.add_point(&proof.a2.get_element());
+        let com_clone = proof.com.clone();
+        let ecom = com_clone.scalar_mul(&e.get_element());


there is something slightly unpleasant about scalar_mul taking mut self while other operations don't. perhaps a Borrow could work and still get the same reuse optimisation when needed? in any case the extra clones could be move into that.

I'm not sure I follow. scalar_mul takes self with the intention to consume self.
This was done to limit the interface. Is this a problem?

not a problem, only saying that the clone could be hidden if desired

can you give an example please?

"hidden" as in moved into the function by letting the function take eg a Cow instead. does that make sense?

mortendahl · 2018-09-03T09:32:55Z

src/cryptographic_primitives/twoparty/dh_key_exchange.rs

+    use cryptographic_primitives::twoparty::dh_key_exchange::*;
+
+    #[test]
+    fn test_full_key_gen() {


I'm wondering if the interface could be changed to avoid this picking of fields, which might cause some confusion or worse down the line. What if eg verify_commitments_and_dlog_proof simply took party_one_first_message and party_one_second_message as arguments?

* ECScalar and ECPoint and the EC specific implementation for Secp256k1Scalar and Secp256k1Point * Commitments: Pedersen, Sigma valid Pedersen blind, Two party coin toss, Key exchange PR: #17 Legacy branch created: https://github.com/KZen-networks/cryptography-utils/tree/two-party-v0

* ECScalar and ECPoint and the EC specific implementation for Secp256k1Scalar and Secp256k1Point * Commitments: Pedersen, Sigma valid Pedersen blind, Two party coin toss, Key exchange PR: ZenGo-X/curv#17 Legacy branch created: https://github.com/KZen-networks/cryptography-utils/tree/two-party-v0

gbenattar and others added 2 commits August 1, 2018 09:20

Removing exposure to context for ser/de utilities

9d3eda5

writing abstraction layer and implement for secp256k1

37e3601

omershlo requested a review from gbenattar August 4, 2018 18:23

omershlo changed the title ~~Rewrite ec abstract~~ Rewrite ec abstract (wip) Aug 4, 2018

omershlo changed the title ~~Rewrite ec abstract (wip)~~ Rewrite ec abstraction (wip) Aug 4, 2018

omershlo added 4 commits August 4, 2018 22:18

dlog proof test

c3a0ab3

adding curve25519 implementation

2cd2424

removed from_key_slice

8cbd304

adding features

4845777

omershlo added 9 commits August 10, 2018 16:42

sha512

e7911e2

removing default

0be5be7

adjusting from_big_int to 64 bytes

8a547cc

adding to ECScalar interface

9193a6d

modulo in from_big_int

1641fce

dealing with curve order bigint

92d2abe

dealing with curve order bigint #2

57aaf93

dealing with curve order bigint #3

ad5a5c7

dealing with curve order bigint #4

898bc2d

omershlo requested review from romanz and mortendahl August 12, 2018 13:40

Apply 'cargo fmt'

596c8f3

romanz force-pushed the rewrite_ec_abstract branch from 4b8027e to 596c8f3 Compare August 12, 2018 14:45

romanz assigned omershlo Aug 12, 2018

Parametrize Travis builds for the elliptic curve

a9d78ef

romanz suggested changes Aug 12, 2018

View reviewed changes

omershlo mentioned this pull request Aug 27, 2018

Review elliptic curve abstraction #18

Closed

omershlo and others added 13 commits August 27, 2018 18:48

serde and serialize from Gary branch

6112dfc

undo serde changes

6ef1b71

compute public key

3ad54a0

compute public key #2

98803bf

hmac-512

ed63faf

compute public key #3

d02d5b8

Remove warning WIP and cargo fmt

e717487

Upgrading to latest secp256k1 and adding serde for Mpz from our package

8959d0d

Adding serde for DLogProof

33242a1

Cargo fmt

f32945b

Fix test warnings

10c4c68

Adding setup script

be02c1d

Adding serde for Secp

7058ac9

mortendahl reviewed Sep 3, 2018

View reviewed changes

gbenattar and others added 5 commits September 4, 2018 10:04

Expose members for other party

36ded94

change visibility for public share

350e3fc

Adding serde annotation

b6c3d61

answering roman and morten review

a1d7217

removing public key from_slice

6578fbb

omershlo changed the title ~~Rewrite ec abstraction (wip)~~ Rewrite ec abstraction Sep 4, 2018

omershlo and others added 6 commits September 4, 2018 15:42

check1

e606f41

answering review

38e3d7b

Returning error for serde

cc6904f

Reverted erased change on member exposure

59101c9

Adding padding for serde

3e2a710

small code cleanup

87fe3ea

omershlo closed this Jan 15, 2019


		pub struct PedersenCommitment;

		impl Commitment<Secp256k1Point> for PedersenCommitment {

Rewrite ec abstraction #17

Rewrite ec abstraction #17

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omershlo commented Aug 4, 2018

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omershlo commented Aug 8, 2018

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romanz commented Aug 12, 2018 •

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