layerxcom/zero-chain

A privacy-preserving blockchain on Substrate

zero-chain's Issues

Avoid using incorrect `rng` traits in wasm

OsRng and ThereadRng can not be used in wasm.We will use ChachaRng for the entropy.

ref: kobigurk/wasm_proof@7389437

Apply to the bullet proofs

Add tests of primitives

Add tests of primitives
https://github.com/LayerXcom/zero-chain/blob/master/proofs/src/primitives/mod.rs

Add test for note.rs

Use travis CI with wasm files in gitignore

wasm files are included here.

zero-chain/src/chain_spec.rs

Lines 86 to 87 in 8cdf89f

	// code: include_bytes!("../runtime/wasm/target/wasm32-unknown-unknown/release/node_template_runtime_wasm.compact.wasm").to_vec(),
	code: include_bytes!("../runtime/wasm/target/wasm32-unknown-unknown/release/zero_chain_runtime_wasm.wasm").to_vec(),

zero-chain/src/service.rs

Lines 30 to 31 in 8cdf89f

	// include_bytes!("../runtime/wasm/target/wasm32-unknown-unknown/release/node_template_runtime_wasm.compact.wasm")
	include_bytes!("../runtime/wasm/target/wasm32-unknown-unknown/release/zero_chain_runtime_wasm.wasm")

Refs:

• https://docs.travis-ci.com/user/environment-variables/
• https://stackoverflow.com/questions/40250937/how-to-use-travis-ci-with-some-files-in-gitignore
• https://stackoverflow.com/questions/42612221/path-to-repository-in-travis

Change AES to MiMC

https://github.com/LayerXcom/zero-chain/blob/master/primitives/src/cm_encryption.rs

// Temporary use for enc/dec
use pcrypto::aes::{
    encrypt_128_ctr, 
    decrypt_128_ctr
};

Applying the self-defined origin/AccountID

Fix key agreement

Update key agreement process for Ed25519 that is used in substrate key store.
I can not use below one because of lack of adopting Ed25519 algorithm, only X25519.
https://briansmith.org/rustdoc/ring/agreement/fn.agree_ephemeral.html

Here is the key exchange algorithm for Ed25519.
https://github.com/DaGenix/rust-crypto/blob/master/src/ed25519.rs#L132-L151

But I need to adopt for key generation of substrate.

ref: https://crypto.stackexchange.com/questions/27866/why-curve25519-for-encryption-but-ed25519-for-signatures

Avoid iterative setups for zkps

Output files of the setup parameters and then read the file for snark proving at the time of tx generation.

Refs:

• https://github.com/Zokrates/ZoKrates/blob/b1fbe401d2466998d373e0d73331e3603b5e7cd8/zokrates_cli/src/bin.rs

Apply no_std mode

Update ECIES scheme

update ECIES scheme to more efficiency and secure.

For wasm, add to zero-chain-proofs

bellman = { git = "https://github.com/osuketh/bellman", branch = "wasm" }
pairing = { git = "https://github.com/sorpaas/pairing", default-features = false }

Ensure if the public attributes are safe in pairing

Ensure if it is needed to change public to public(crate).

zero-chain/pairing/src/bls12_381/ec.rs

Lines 15 to 17 in 9d712d9

	pub x: $basefield,
	pub y: $basefield,
	pub infinity: bool

zero-chain/pairing/src/bls12_381/fq.rs

Line 701 in 9d712d9

pub struct Fq(pub FqRepr);

But if these are changed, the test of bellman-verifier would be failed because the proof is hard-coded, it cannot access as these fields are private out of the pairing crate.

zero-chain/bellman-verifier/src/lib.rs

Lines 272 to 294 in 9d712d9

	let proof = Proof::<Bls12> {
	a: G1Affine {
	x: Fq(FqRepr([16739797345307447054, 8770073581945912782, 2136235734558249053, 15708693206467346864, 8490922573673252286, 1579948179538746271])),
	y: Fq(FqRepr([6020268861830312380, 12879642226817054130, 17904268384441769431, 15221266273771162992, 5384025118770475327, 1217424206270675696])),
	infinity: false
	},
	b: G2Affine {
	x: Fq2 {
	c0: Fq(FqRepr([1955900693533848923, 1207270260807916624, 10030599496790334806, 13310839817113796132, 7335494448760471336, 1520001478562200471])),
	c1: Fq(FqRepr([10867545881237734656, 11292327308906943064, 4286427264655280722, 5033346395315998832, 9316987264960049565, 1093242448245841130]))
	},
	y: Fq2 {
	c0: Fq(FqRepr([6242954237310667968, 4585560269108097072, 5517602464819718440, 11574556308726901230, 9576729709326690239, 433440758793164942])),
	c1: Fq(FqRepr([11180820212476238720, 13504112200989036594, 2176986271111729977, 4481942420924131750, 16599268505710547724, 922146901424495142]))
	},
	infinity: false
	},
	c: G1Affine {
	x: Fq(FqRepr([16362720867114782945, 14827736289902972547, 7987695302896742039, 14289613131851611182, 7162884718192410854, 605698044002088945])),
	y: Fq(FqRepr([3093450141616622888, 7767002491037351418, 5972324121568597438, 2377138492074911281, 701452421528324862, 1373508511228186748])),
	infinity: false
	}
	};

Integrate own constants for primitives

Add error handling for cm_encryption

Avoid using unwrap() in https://github.com/LayerXcom/zero-chain/blob/master/primitives/src/cm_encryption.rs

Consider the bit length of ElGamal-encrypted value

In order to decrypt the lifted-Elgamal encryption, it is needed to solve the discrete logarithm.
That is why the decryption is inefficiency. Needed to consider the bit length depending on computational times.

zero-chain/crypto/src/elgamal.rs

Lines 61 to 66 in 8cdf89f

	// for i in 0..u32::MAX {
	for i in 0..1000 { // FIXME:
	if find_point(i, &v_point, p_g, params) {
	return Some(i);
	}
	}

Re-added proof verification in proving function

Temporary removed because the prepared_verification_key can not read in bellman(std).

zero-chain/core/proofs/src/prover.rs

Lines 147 to 148 in 541f307

	// verify_proof(prepared_vk, &proof, &public_input[..])
	// .expect("verifying should not fail");

Protect front running attacks

Add the pending transfer.
In the confidential transfer function, add epoch_check, roll over pendings and update last_epoch.

pub fn confTransfer() {
  RollOver(sender_addr)
  RollOver(recipient_addr)
  ・・・
  balances[sender_addr] += Enc(-value)
  pending_transfer[recipient_addr] += Enc(value)
  ・・・
}

fn RollOver(addr) {
  let H = block.number
  let e = H/E
  if lastRollOver[addr] < e:
    Set balance[addr] += pending_transfer[addr]
    Set pending_transfer[addr] = (1, 1)
    Set lastRollOver[addr] = e
}

In the storage, Add pending_transfer_map and last_epoch_map

storage{
  pending_transfer: map address => pending_value
  last_epoch: map address => block_height
  ・・・
}

Apply wasm for the web wallet

Implement the lifted-ElGamal decryption algorithm out of circuit

[Part 1] Define parameters of confidential transfers and inputs of zk proof

parameters of confidential transfers

• commitment root (anchor)
  A treestate consists of a note commitment tree and a nullifier set. The nullifier set is always updated together with the note commitment tree.
  The input treestate of each subsequent transaction in a block is the output treestate of the immediately preceding transaction.
  Namely, an anchor is the output treestate of either a previous block, or a previous JoinSplit transfer in this transaction

• nullifier
  nullifier for the input note.

• Note commitment:
  note commitment for the output note.

• public key
  a key agreement public key, used to derive the key for encryption of the transmitted notes ciphertext.

• random
  a seed that must be chosen independently at random for each transactions.

• tag
  a tag that bind h_sig to each private key of the input notes
  where h_sig = hash(random, nullifier, pubkey)
  In order to avoid malleability.

• zk proof
  a zero knowledge proof

• encrypted Note
  ciphertext components for the encrypted output note.

inputs of zk proof

primary input (public)

• commitment root
• nullifier
• Note commitment
• h_sig
• tag

auxiliary inputs (private)

• merkle path
• position
• Note_old
• Note_new
• private key
• phi (for uniquness of rho)
• merkle path enforcement

Add MiMC circuit

Implement MiMC circuit in bellman.

Add overflow checking for the encrypted value

Currently, there are not any overflow checking for the encrypted value. Add overflow checking or some restriction for the value.

zero-chain/crypto/src/elgamal.rs

Line 30 in e9a60f6

value: u32, // 32-bits restriction for the decryption.

Implement CLI

like

init: // each account has 100 unit at the time of initialization
 	- address0: 0xaa
 	- spending_key0: 0x4ab
 	- address1: 0xab
 	- spending_key1: 0x1c8
 	・・・
 transfer 0xab<receiver> 10<amount> 0x4ab<spending_key>
 	- success
 balance 0xaa<addr> 0x4ab<spending_key>
 	- 90
 all_balances
 	- 0xaa => 0xdaf
 	- 0xab => 0xfa3
 	・・・

Inside the transfer would be

transfer(sender, receiver, amount, sk) {
 	r,v = api::get_balance(sender) // GET
 	proof = prove() // embedded params
 	enc = encrypt()
 	tx = gen_tx()
 	runtime_api::execute_block() // POST
 }

For getting the balances, needed decryption.

 get_balance(addr) -> r, v {
 	enc = get_storage(addr, from_index)
 	p = dec(enc)
 	calc(p)
 }

Add attributes for structs

In order to send the own defined struct to substrate, needed to add attributes of Encode, Decode, Default.

Implement the homomorphic encryption in circuit

For simplicity, we should add the homomorphic encryption like ElGamal or lifted-ElGamal, paillier instead of pedersen commitment.

`<Bls12>` and `<JubjubBls12>`

Ensure the difference between <Bls12> and <JubjubBls12> as a Engine.

To be compatible with the ethereum smart contracts

Add ECIES for encryption and decryption Note

Fix the test of zk_proof byte-cast.

The test fails because the dummy_engine is not implemented the from_affine() for the test.

error logs

---- proof::tests::test_proof_into_from stdout ----
thread 'proof::tests::test_proof_into_from' panicked at 'not yet implemented', bellman-verifier/src/tests/dummy_engine.rs:400:9
note: Run with `RUST_BACKTRACE=1` for a backtrace.

zero-chain/primitives/src/proof.rs

Lines 94 to 106 in da32bd7

	fn test_proof_into_from() {
	// let mut rng = &mut XorShiftRng::from_seed([0x3dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0654]);
	// let proof1 = bellman_verifier::Proof::<DummyEngine> {
	// a: Fr(Wrapping(3269)),
	// b: Fr(Wrapping(471)),
	// c: Fr(Wrapping(8383)),
	// };
	// let proof_b = Proof::test_from_proof(&proof1);
	// println!("proof_b: {:?}", proof_b);
	// let proof2 = proof_b.test_into_proof().unwrap();
	// assert!(proof1 == proof2);

Fix the variable name of `ExpandedSpendingKey` to `ExtendedSpendingKey`

https://github.com/LayerXcom/zero-chain/blob/master/proofs/src/primitives/mod.rs

Ensure preventing from small subgroup attacks

Add low order checks to primitives

Add low order checks to primitives at the time of reading from bytes to types.

Add jubjbubls12 params as aglobal variable into UI

Ensure the byteorder is correct

https://github.com/LayerXcom/zero-chain/blob/master/primitives/src/cm_encryption.rs

let mut plaintext = vec![];
        // TODO: Ensure the byteorder is correct
        (&mut plaintext).write_u64::<LittleEndian>(self.value).unwrap();
        (&mut plaintext).write_u64::<LittleEndian>(self.randomness).unwrap();  

`<,Unknown>` and `<,PrimeOrder>

Ensure the correct Subgroup for edwards::Point

Make correct sig hash for the compatibility with substrate

Need to be compatible with the signed data field between signing and verifying.

In unchecked_mortal_compact_extrinsic, the signature verification is implemented here.
https://github.com/paritytech/substrate/blob/1997487ec082f436e4c3279402d4528d67c861be/core/sr-primitives/src/generic/unchecked_mortal_compact_extrinsic.rs#L85-L96

In oo7, the signing scheme is implemented here.
https://github.com/paritytech/oo7/blob/79856e56658ad2b71115af5f682ac5d71a4f9ab3/packages/oo7-substrate/src/transact.js#L27-L42

Implement decryption for `Ciphertext`

zero-chain/primitives/src/cm_encryption.rs

Line 111 in 0cbfe71

// impl<E: JubjubEngine> Ciphertext<E> {

Fix something wrong with the pairing test for a swap of the endian

zero-chain/pairing/src/tests/repr.rs

Lines 38 to 54 in 49eb9d1

	{
	let mut rdecoded_le = R::default();
	let mut rdecoded_be_flip = R::default();
	let mut v: Vec<u8> = vec![];
	r.write_le(&mut &mut v).unwrap();
	// This reads in little-endian, so we are done.
	rdecoded_le.read_le(&mut &v[..]).unwrap();
	// This reads in big-endian, so we perform a swap of the
	// bytes beforehand.
	let v: Vec<u8> = v.into_iter().rev().collect();
	rdecoded_be_flip.read_be(&mut &v[..]).unwrap();
	assert_eq!(rdecoded_le, rdecoded_be_flip);
	}

got the following error.

thread 'bls12_381::fq::fq_repr_tests' panicked at 'assertion failed: `(left == right)`
  left: `FqRepr([5457830654796382876, 14052294085650741142, 9037930377914938456, 17127803672399921366, 8651480755814397574, 10649476550251866400])`,
 right: `FqRepr([10649476550251866400, 8651480755814397574, 17127803672399921366, 9037930377914938456, 14052294085650741142, 5457830654796382876])`', pairing/src/tests/repr.rs:53:13
note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
test bls12_381::fq::fq_repr_tests ... FAILED

"Zframe" as a privacy oriented blockchain framework

"Zerochain" would be a our public chain using Zframe.

Add appropriate storage in SRML

map nullifier => hash(Note)
map hash(account) => encNote
Vec<u8> root of commitment tree

Add byte casts for transaction components

Implement the byte casted types of transaction components for substrate.

Move nonce_increment logic from `executive` to `conf_transfer`

Currently, the nonces are tied with each one-time signature verification key in the executive logic, so we need to get it tied with pkd_address (aka account id).

Replace bellman dependencies from original crates to no_std crates

It makes simple to use std and no_std dependencies. It means it is enable to use same pairing and jubjub crates in both std and no_std environment.

Ensure if `reader` is consumed in no_std

zero-chain/bellman-verifier/src/lib.rs

Lines 68 to 96 in 9d712d9

	reader.read(g1_repr.as_mut())?;
	let a = g1_repr
	.into_affine()
	.map_err(|_| io::Error::InvalidData)
	.and_then(|e| if e.is_zero() {
	Err(io::Error::PointInfinity)
	} else {
	Ok(e)
	})?;
	reader.read(g2_repr.as_mut())?;
	let b = g2_repr
	.into_affine()
	.map_err(|_| io::Error::InvalidData)
	.and_then(|e| if e.is_zero() {
	Err(io::Error::PointInfinity)
	} else {
	Ok(e)
	})?;
	reader.read(g1_repr.as_mut())?;
	let c = g1_repr
	.into_affine()
	.map_err(|_| io::Error::InvalidData)
	.and_then(|e| if e.is_zero() {
	Err(io::Error::PointInfinity)
	} else {
	Ok(e)
	})?;

Each of read function should consume the reader data.

Update the substrate `runtime` and `src`

Currently, the part of node-template is outdated.
Needed update in order to build and run substrate's chain.

Gav said the version of node-template would be freezed in a couple of weeks.

Ref:
https://github.com/paritytech/substrate/tree/master/node-template

Move the integration test for zk proof to appropriate path

The integration test that is reading proving_key and preapred_vk binary files, then proving and verifying is in core/proofs/src/prover.rs.

zero-chain/proofs/src/prover.rs

Line 173 in 90ebbfe

fn test_gen_proof() {

Implement the client of sending a transaction to substrate

It would be implemented in Rust and the interface of POST and GET would be in CLI.

Add module logic, storage and event on substrate

https://github.com/LayerXcom/zero-chain/blob/master/runtime/src/confidential_transfer.rs

Implement `sighash`