Rust BLS child key derivation (EIP2333, EIP2334)

This library is a forked version of bls_key_derivation, containing a straightforward interface to BLS12-381 child key derivation in complete compliance with EIP2333.

Since EIP2333 only proposes the hardened child key derivation, this library has also implemented a method of non-hardened child key derivation inspired by BIP32 to support the current application scenarios.

Changes

Differences with the original library (https://github.com/ChainSafe/rust-bls-derivation) lie in the following:

1. removing the dependency on the unmaintained-for-over-6-years crate rust-crypto;
2. adding the active crate curv-kzen to support non-hardened BLS child key derivation beyond EIP233;
3. changing the lower limit of the seed entropy from 16 bytes to 32 bytes to be consistent with the current EIP2333 and draft-irtf-cfrg-bls-signature-05;
4. particularly modifying the function hkdf_mod_r in the following 5 parts to be in complete compliance with both EIP2333 and KeyGen in Section 2.3 of draft-irtf-cfrg-bls-signature-05:
   1. IKM -> IMK || I20SP(0, 1);
   2. keyinfo -> keyinfo || I20SP(L, 2);
   3. salt -> H(salt);
   4. add a loop with the zero private key check;
   5. add an input parameter key_info to support user-customized key info strings instead of fixing as a default empty string "".

Usage

Defined in the crate curv, FE is the scalar type in $G_1$ and $G_2$, with GE1 and GE2 as point types, respectively. The following generic type T should be either GE1 or GE2.

CKD hardened

private->private hardened child key derivation:

pub fn ckd_sk_hardened(parent_sk: &FE, index: u32) -> FE

private->private hardened child key derivation from a path:

pub fn derive_child_sk(parent_sk: FE, path_str: &str) -> FE

master private key derivation from a seed:

pub fn derive_master_sk(seed: &[u8]) -> Result<FE, String>

Get indexes from a string path following EIP2334 spec:

pub fn path_to_node(path_str: &str) -> Result<Vec<u32>, String>

CKD non-hardened

private->private non-hardened child key derivation:

pub fn ckd_sk_norma::<T>(parent_sk: &FE, index: u32) -> FE

private->private non-hardened child key derivation from a path:

pub fn derive_child_sk_normal::<T>(parent_sk: FE, path_str: &str) -> FE

public->public non-hardened child key derivation:

pub fn ckd_pk_normal(parent_pk: &T, index: u32) -> T

public->public non-hardened child key derivation from a path:

pub fn derive_child_pk_normal(parent_pk: T, path_str: &str) -> T

Compute the scalar tweak added to this key to get a child key:

pub fn ckd_tweak_normal(parent_pk: &T, index: u32) -> FE

Testing

run tests with:

cargo test