testsuite/cli/diem-wallet/README.md
Diem Wallet is a pure-rust implementation of hierarchical key derivation for SecretKey material in Diem.
diem-wallet is a library providing hierarchical key derivation for SecretKey material in Diem. The following crate is largely inspired by rust-wallet with minor modifications to the key derivation function. Note that Diem makes use of the ed25519 Edwards Curve Digital Signature Algorithm (EdDSA) over the Edwards Cruve cruve25519. Therefore, BIP32-like PublicKey derivation is not possible without falling back to a traditional non-deterministic Schnorr signature algorithm. For this reason, we modified the key derivation function to a simpler alternative.
The internal_macros.rs is taken from rust-bitcoin and mnemonic.rs is a slightly modified version of the file with the same name from rust-wallet, while error.rs, key_factor.rs and wallet_library.rs are modified to present a minimalist wallet library for the Diem Client. Note that mnemonic.rs from rust-wallet adheres to the BIP39 spec.
key_factory.rs implements the key derivation functions. The KeyFactory struct holds the Master Secret Material used to derive the Child Key(s). The constructor of a particular KeyFactory accepts a [u8; 64] Seed and computes both the Master Secret Material as well as the ChainCode from the HMAC-512 of the Seed. Finally, the KeyFactory allows to derive a child PrivateKey at a particular ChildNumber from the Master and ChainCode, as well as the ChildNumber's u64 member.
wallet_library.rs is a thin wrapper around KeyFactory which enables to keep track of Diem AccountAddresses and the information required to restore the current wallet from a Mnemonic backup. The WalletLibrary struct includes constructors that allow to generate a new WalletLibrary from OS randomness or generate a WalletLibrary from an instance of Mnemonic. WalletLibrary also allows to generate new addresses in-order or out-of-order via the fn new_address and fn new_address_at_child_number. Finally, WalletLibrary is capable of signing a Diem RawTransaction with the PrivateKey associated to the AccountAddress submitted. Note that in the future, Diem will support rotating authentication keys and therefore, WalletLibrary will need to understand more general inputs when mapping AuthenticationKeys to PrivateKeys