hcseedbundle

SeedBundle parsing and generation library.

Rationale

Applications like Holochain have different requirements than classic blockchain systems in terms of key management. Namely there is no need for read-only or hardened wallets (Holochain handles these concepts through capabilities and membranes).
Applications like Holochain still have need of hierarchy and determinism in key (or in this case seed) derivation.
Since we're using libsodium for hashing, signature, and encryption algorithms, let's use it for derivation as well.
To be psychologically compatible with the Bitcoin "HD Wallet" spec, we will do away with the "context" part of sodium KDF by always setting it to b"SeedBndl" and focusing on the subkey_id and can declare a chain of subsequent derivations of a 32 byte seed in the form m/68/1/65/8 where we apply subkey_ids 68, 1, 65, then 8 in turn.

hcSeedBundle Encoding Spec

Encoded in MSGPACK binary format.

To better facilitate rust/javascript interoperability, the rust library will treat msgpack "ext" types as binary data.

SeedBundle

``` // seedbundle is a top-level array 'seedbundle':array [ // literal 'hcsb0' version / heuristic marker 'id_ver':str,

// list of SeedCiphers define how to decrypt 'cipherlist':array [ 'cipher1':SeedCipher, 'cipher2':SeedCipher, // .. 'cipherN':SeedCipher, ],

// associated application data 'app_data':bin, ] ```

SeedCipher::PwHash

``` // the PwHash type SeedCipher defines a straight-forward // pwhash secret that is use to secretstream encrypt a seed 'seed_cipher':array [ // literal 'pw' indicates the pw hash cipher type 'type':str,

// argon2id 16 byte salt 'salt':bin,

// argon2id mem limit capped to u32 for js compatibility 'mem_limit':int,

// argon2id ops limit capped to u32 for js compatibility 'ops_limit':int,

// secretstream 24 byte header 'header':bin,

// secretstream 49 byte cipher 'cipher':bin, ] ```

SeedCipher::SecurityQuestions

``` // Security Questions SeedCipher defines a pwhash cipher // based on concatonating 3 answers that are lcased/trimmed 'seed_cipher':array [ // literal 'qa' indicates the security question cipher type 'type':str,

// argon2id 16 byte salt 'salt':bin,

// argon2id mem limit capped to u32 for js compatibility 'mem_limit':int,

// argon2id ops limit capped to u32 for js compatibility 'ops_limit':int,

// the first security question to be answered 'question_1':str,

// the second security question to be answered 'question_2':str,

// the third security question to be answered 'question_3':str,