keyfork-derive-util: add doctests/examples

crates/derive/keyfork-derive-util/src/extended_key/private_key.rs

@@ -68,14 +68,27 @@ where
     /// mnemonic, but may take 16-byte seeds.
     ///
     /// # Panics
-    ///
     /// The method performs unchecked `try_into()` operations on a constant-sized slice.
     ///
     /// # Errors
-    ///
     /// An error may be returned if:
     /// * The given seed had an incorrect length.
     /// * A `HmacSha512` can't be constructed - this should be impossible.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// #   private_key::TestPrivateKey as PrivateKey,
+    /// # };
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let seed: &[u8; 64] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// let xprv = ExtendedPrivateKey::<PrivateKey>::new(seed)?;
+    /// # Ok(())
+    /// # }
+    /// ```
     pub fn new(seed: impl AsRef<[u8]>) -> Result<Self> {
         Self::new_internal(seed.as_ref())
     }
@@ -104,6 +117,23 @@ where
     ///
     /// # Errors
     /// The function may error if a private key can't be created from the seed.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// #   private_key::TestPrivateKey as PrivateKey,
+    /// # };
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let key: &[u8; 32] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// let chain_code: &[u8; 32] = //
+    /// #   b"BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB";
+    /// let xprv = ExtendedPrivateKey::<PrivateKey>::new_from_parts(key, 4, *chain_code)?;
+    /// # Ok(())
+    /// # }
+    /// ```
     pub fn new_from_parts(seed: &[u8], depth: u8, chain_code: [u8; 32]) -> Result<Self> {
         Ok(Self {
             private_key: K::from_bytes(seed.try_into()?),
@@ -113,26 +143,123 @@ where
     }
 
     /// Returns a reference to the [`PrivateKey`].
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   private_key::PrivateKey as _,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// #   private_key::TestPrivateKey as PrivateKey,
+    /// # };
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let key: &[u8; 32] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// let chain_code: &[u8; 32] = //
+    /// #   b"BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB";
+    /// let xprv = ExtendedPrivateKey::<PrivateKey>::new_from_parts(key, 4, *chain_code)?;
+    /// assert_eq!(xprv.private_key(), &PrivateKey::from_bytes(key));
+    /// # Ok(())
+    /// # }
+    /// ```
     pub fn private_key(&self) -> &K {
         &self.private_key
     }
 
     /// Create an [`ExtendedPublicKey`] for the current [`PrivateKey`].
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   private_key::PrivateKey as _,
+    /// #   public_key::PublicKey as _,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// #   private_key::TestPrivateKey as PrivateKey,
+    /// # };
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let seed: &[u8; 64] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// # let known_key: [u8; 33] = [
+    /// # 0, 242, 26, 9, 159, 68, 199, 0, 206, 71, 248,
+    /// # 102, 201, 210, 159, 219, 222, 42, 201, 44, 196, 27,
+    /// # 90, 221, 80, 85, 135, 79, 39, 253, 223, 35, 251
+    /// # ];
+    /// let xprv = ExtendedPrivateKey::<PrivateKey>::new(seed)?;
+    /// let xpub = xprv.extended_public_key();
+    /// assert_eq!(known_key, xpub.public_key().to_bytes());
+    /// # Ok(())
+    /// # }
+    /// ```
     pub fn extended_public_key(&self) -> ExtendedPublicKey<K::PublicKey> {
-        ExtendedPublicKey::new(self.public_key(), self.chain_code)
+        ExtendedPublicKey::new_from_parts(self.public_key(), self.depth, self.chain_code)
     }
 
     /// Return a public key for the current [`PrivateKey`].
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   private_key::PrivateKey as _,
+    /// #   public_key::PublicKey as _,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// #   private_key::TestPrivateKey as PrivateKey,
+    /// # };
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let seed: &[u8; 64] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// let xprv = ExtendedPrivateKey::<PrivateKey>::new(seed)?;
+    /// let pubkey = xprv.public_key();
+    /// # Ok(())
+    /// # }
+    /// ```
     pub fn public_key(&self) -> K::PublicKey {
         self.private_key.public_key()
     }
 
     /// Returns the current depth.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// #   private_key::TestPrivateKey as PrivateKey,
+    /// # };
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let key: &[u8; 32] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// let chain_code: &[u8; 32] = //
+    /// #   b"BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB";
+    /// let xprv = ExtendedPrivateKey::<PrivateKey>::new_from_parts(key, 4, *chain_code)?;
+    /// assert_eq!(xprv.depth(), 4);
+    /// # Ok(())
+    /// # }
+    /// ```
     pub fn depth(&self) -> u8 {
         self.depth
     }
 
     /// Returns a copy of the current chain code.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// #   private_key::TestPrivateKey as PrivateKey,
+    /// # };
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let key: &[u8; 32] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// let chain_code: &[u8; 32] = //
+    /// #   b"BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB";
+    /// let xprv = ExtendedPrivateKey::<PrivateKey>::new_from_parts(key, 4, *chain_code)?;
+    /// assert_eq!(chain_code, &xprv.chain_code());
+    /// # Ok(())
+    /// # }
+    /// ```
     pub fn chain_code(&self) -> [u8; 32] {
         self.chain_code
     }
@@ -140,9 +267,29 @@ where
     /// Derive a child using the given [`DerivationPath`].
     ///
     /// # Errors
-    ///
     /// An error may be returned under the same circumstances as
     /// [`ExtendedPrivateKey::derive_child`].
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// #   private_key::TestPrivateKey as PrivateKey,
+    /// # };
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let seed: &[u8; 64] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// let root_xprv = ExtendedPrivateKey::<PrivateKey>::new(seed)?;
+    /// let path = DerivationPath::default()
+    ///     .chain_push(DerivationIndex::new(44, true)?)
+    ///     .chain_push(DerivationIndex::new(0, true)?)
+    ///     .chain_push(DerivationIndex::new(0, true)?)
+    ///     .chain_push(DerivationIndex::new(0, false)?);
+    /// let derived_xprv = root_xprv.derive_path(&path)?;
+    /// # Ok(())
+    /// # }
+    /// ```
     pub fn derive_path(&self, path: &DerivationPath) -> Result<Self> {
         if path.path.is_empty() {
             Ok(self.clone())
@@ -165,6 +312,33 @@ where
     /// * The depth exceeds the maximum depth [`u8::MAX`].
     /// * A `HmacSha512` can't be constructed - this should be impossible.
     /// * Deriving a child key fails. Check the documentation for your [`PrivateKey`].
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// #   private_key::TestPrivateKey as PrivateKey,
+    /// # };
+    /// # fn check_empty(p: &ExtendedPrivateKey<PrivateKey>) -> Result<(), std::io::Error> {
+    /// # Ok(())
+    /// # }
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let seed: &[u8; 64] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// let root_xprv = ExtendedPrivateKey::<PrivateKey>::new(seed)?;
+    /// let bip44_wallet = DerivationPath::default()
+    ///     .chain_push(DerivationIndex::new(44, true)?)
+    ///     .chain_push(DerivationIndex::new(0, true)?)
+    ///     .chain_push(DerivationIndex::new(0, true)?)
+    ///     .chain_push(DerivationIndex::new(0, false)?);
+    /// let change_xprv = root_xprv.derive_path(&bip44_wallet)?;
+    /// for account in (0..20).map(|i| DerivationIndex::new(i, false).unwrap()) {
+    ///     let account_xprv = change_xprv.derive_child(&account)?;
+    ///     check_empty(&account_xprv)?;
+    /// }
+    /// # Ok(())
+    /// # }
     pub fn derive_child(&self, index: &DerivationIndex) -> Result<Self> {
         let depth = self.depth.checked_add(1).ok_or(Error::Depth)?;
 

crates/derive/keyfork-derive-util/src/extended_key/public_key.rs

@@ -44,15 +44,51 @@ where
     K: PublicKey,
 {
     /// Create a new [`ExtendedPublicKey`] from previously known values.
-    pub fn new(public_key: K, chain_code: ChainCode) -> Self {
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   public_key::PublicKey as _,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// # };
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let key: &[u8; 33] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// let chain_code: &[u8; 32] = //
+    /// #   b"BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB";
+    /// let pubkey = PublicKey::from_bytes(key);
+    /// let xpub = ExtendedPublicKey::<PublicKey>::new_from_parts(pubkey, 0, *chain_code);
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn new_from_parts(public_key: K, depth: u8, chain_code: ChainCode) -> Self {
         Self {
             public_key,
-            depth: 0,
+            depth,
             chain_code,
         }
     }
 
     /// Return the internal [`PublicKey`].
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   public_key::PublicKey as _,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// # };
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// # let key: &[u8; 33] = b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// # let chain_code: &[u8; 32] = b"BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB";
+    /// # let pubkey = PublicKey::from_bytes(key);
+    /// let xpub = //
+    /// # ExtendedPublicKey::<PublicKey>::new_from_parts(pubkey, 0, *chain_code);
+    /// let pubkey = xpub.public_key();
+    /// # Ok(())
+    /// # }
+    /// ```
     pub fn public_key(&self) -> &K {
         &self.public_key
     }
@@ -70,6 +106,25 @@ where
     /// * The depth exceeds the maximum depth [`u8::MAX`].
     /// * A `HmacSha512` can't be constructed - this should be impossible.
     /// * Deriving a child key fails. Check the documentation for your [`PublicKey`].
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   public_key::PublicKey as _,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// # };
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// # let key: &[u8; 33] = b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// # let chain_code: &[u8; 32] = b"BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB";
+    /// # let pubkey = PublicKey::from_bytes(key);
+    /// let xpub = //
+    /// # ExtendedPublicKey::<PublicKey>::new_from_parts(pubkey, 0, *chain_code);
+    /// let index = DerivationIndex::new(0, false)?;
+    /// let child = xpub.derive_child(&index)?;
+    /// # Ok(())
+    /// # }
+    /// ```
     pub fn derive_child(&self, index: &DerivationIndex) -> Result<Self> {
         if index.is_hardened() {
             return Err(Error::HardenedIndex);

crates/derive/keyfork-derive-util/src/index.rs

@@ -23,8 +23,20 @@ impl DerivationIndex {
     /// Creates a new [`DerivationIndex`].
     ///
     /// # Errors
-    ///
     /// Returns an error if the index is larger than the hardened flag.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::*;
+    /// let bip44 = DerivationIndex::new(44, true);
+    /// ```
+    ///
+    /// Using a derivation index that is higher than 2^31 returns an error:
+    ///
+    /// ```rust,should_panic
+    /// # use keyfork_derive_util::*;
+    /// let too_high = DerivationIndex::new(u32::MAX, true).unwrap();
+    /// ```
     pub const fn new(index: u32, hardened: bool) -> Result<Self> {
         if index & (0b1 << 31) > 0 {
             return Err(Error::IndexTooLarge(index));
@@ -46,6 +58,13 @@ impl DerivationIndex {
 
     /// Return the internal derivation index. Note that if the derivation index is hardened, the
     /// highest bit will be set, and the value can't be used to create a new derivation index.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::*;
+    /// assert_eq!(DerivationIndex::new(44, true).unwrap().inner(), 2147483692);
+    /// assert_eq!(DerivationIndex::new(200, false).unwrap().inner(), 200);
+    /// ```
     pub fn inner(&self) -> u32 {
         self.0
     }
@@ -54,7 +73,15 @@ impl DerivationIndex {
         self.0.to_be_bytes()
     }
 
-    /// Whether or not the index is hardened, allowing deriving the key from a known parent key.
+    /// Whether or not the index is hardened, allowing deriving the key from a known parent public
+    /// key.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::*;
+    /// assert_eq!(DerivationIndex::new(0, true).unwrap().is_hardened(), true);
+    /// assert_eq!(DerivationIndex::new(0, false).unwrap().is_hardened(), false);
+    /// ```
     pub fn is_hardened(&self) -> bool {
         self.0 & (0b1 << 31) != 0
     }

crates/derive/keyfork-derive-util/src/path.rs

@@ -52,6 +52,24 @@ impl DerivationPath {
     }
 
     /// Append an index to the path, returning self to allow chaining method calls.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::*;
+    /// # fn discover_wallet(_p: DerivationPath) -> Result<bool, std::io::Error> { Ok(true) }
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let account = 0;
+    /// let path = DerivationPath::default()
+    ///     .chain_push(DerivationIndex::new(44, true)?)
+    ///     .chain_push(DerivationIndex::new(0, true)?)
+    ///     .chain_push(DerivationIndex::new(account, true)?);
+    /// let mut has_wallet = false;
+    /// for index in (0..20).map(|i| DerivationIndex::new(i, true).unwrap()) {
+    ///     has_wallet = has_wallet || discover_wallet(path.clone().chain_push(index))?;
+    /// }
+    /// # Ok(())
+    /// # }
+    /// ```
     pub fn chain_push(mut self, index: DerivationIndex) -> Self {
         self.path.push(index);
         self

crates/derive/keyfork-derive-util/src/private_key.rs

@@ -13,9 +13,32 @@ pub trait PrivateKey: Sized {
     type Err: std::error::Error;
 
     /// Create a Self from bytes.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   private_key::TestPrivateKey as OurPrivateKey,
+    /// # };
+    /// let key_data: &[u8; 32] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// let private_key = OurPrivateKey::from_bytes(key_data);
+    /// ```
     fn from_bytes(b: &PrivateKeyBytes) -> Self;
 
     /// Convert a &Self to bytes.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   private_key::TestPrivateKey as OurPrivateKey,
+    /// # };
+    /// let key_data: &[u8; 32] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// let private_key = OurPrivateKey::from_bytes(key_data);
+    /// assert_eq!(key_data, &private_key.to_bytes());
+    /// ```
     fn to_bytes(&self) -> PrivateKeyBytes;
 
     /*
@@ -27,12 +50,35 @@ pub trait PrivateKey: Sized {
     */
 
     /// The initial key for BIP-0032 and SLIP-0010 derivation, such as secp256k1's "Bitcoin seed".
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   private_key::TestPrivateKey as OurPrivateKey,
+    /// # };
+    /// assert_eq!(OurPrivateKey::key(), "testing seed");
+    /// ```
     fn key() -> &'static str;
 
     /// Generate a [`Self::PublicKey`].
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   private_key::TestPrivateKey as OurPrivateKey,
+    /// # };
+    /// let key_data: &[u8; 32] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// let private_key = OurPrivateKey::from_bytes(key_data);
+    /// let public_key = private_key.public_key();
+    /// ```
     fn public_key(&self) -> Self::PublicKey;
 
-    /// Derive a child [`PrivateKey`] with given `PrivateKeyBytes`.
+    /// Derive a child [`PrivateKey`] with given `PrivateKeyBytes`. The implementation of
+    /// derivation is algorithm-specific and a specification should be consulted when implementing
+    /// this method.
     ///
     /// # Errors
     ///
@@ -129,3 +175,48 @@ impl PrivateKey for ed25519_dalek::SigningKey {
         true
     }
 }
+
+use crate::public_key::TestPublicKey;
+
+#[doc(hidden)]
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct TestPrivateKey {
+    key: [u8; 32],
+}
+
+impl TestPrivateKey {
+    pub(crate) fn public_key(&self) -> TestPublicKey {
+        let mut bytes = [0u8; 33];
+        for (i, byte) in self.key.iter().enumerate() {
+            bytes[i + 1] = byte ^ 0xFF;
+        }
+        TestPublicKey { key: bytes }
+    }
+}
+
+impl PrivateKey for TestPrivateKey {
+    type PublicKey = TestPublicKey;
+    type Err = PrivateKeyError;
+
+    fn from_bytes(b: &PrivateKeyBytes) -> Self {
+        Self {
+            key: *b
+        }
+    }
+
+    fn to_bytes(&self) -> PrivateKeyBytes {
+        self.key
+    }
+
+    fn key() -> &'static str {
+        "testing seed"
+    }
+
+    fn public_key(&self) -> Self::PublicKey {
+        self.public_key()
+    }
+
+    fn derive_child(&self, other: &PrivateKeyBytes) -> Result<Self, Self::Err> {
+        Ok(Self { key: *other })
+    }
+}

crates/derive/keyfork-derive-util/src/public_key.rs

@@ -19,9 +19,23 @@ pub trait PublicKey: Sized {
     */
 
     /// Convert a &Self to bytes.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   private_key::TestPrivateKey as OurPrivateKey,
+    /// # };
+    /// let key_data: &[u8; 32] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// let private_key = OurPrivateKey::from_bytes(key_data);
+    /// let public_key_bytes = private_key.public_key().to_bytes();
+    /// ```
     fn to_bytes(&self) -> PublicKeyBytes;
 
-    /// Derive a child [`PublicKey`] with given `PrivateKeyBytes`.
+    /// Derive a child [`PublicKey`] with given `PrivateKeyBytes`. The implementation of
+    /// derivation is algorithm-specific and a specification should be consulted when implementing
+    /// this method.
     ///
     /// # Errors
     ///
@@ -31,6 +45,18 @@ pub trait PublicKey: Sized {
     fn derive_child(&self, other: PrivateKeyBytes) -> Result<Self, Self::Err>;
 
     /// Create a BIP-0032/SLIP-0010 fingerprint from the public key.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   private_key::TestPrivateKey as OurPrivateKey,
+    /// # };
+    /// let key_data: &[u8; 32] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// let private_key = OurPrivateKey::from_bytes(key_data);
+    /// let fingerprint = private_key.public_key().fingerprint();
+    /// ```
     fn fingerprint(&self) -> [u8; 4] {
         let hash = Sha256::new().chain_update(self.to_bytes()).finalize();
         let hash = Ripemd160::new().chain_update(hash).finalize();
@@ -112,3 +138,32 @@ impl PublicKey for VerifyingKey {
         Err(Self::Err::DerivationUnsupported)
     }
 }
+
+#[doc(hidden)]
+#[derive(Clone)]
+pub struct TestPublicKey {
+    pub(crate) key: [u8; 33],
+}
+
+impl TestPublicKey {
+    #[doc(hidden)]
+    pub fn from_bytes(b: &[u8]) -> Self {
+        Self {
+            key: b.try_into().unwrap(),
+        }
+    }
+
+}
+
+impl PublicKey for TestPublicKey {
+    type Err = PublicKeyError;
+
+    fn to_bytes(&self) -> PublicKeyBytes {
+        self.key
+    }
+
+    fn derive_child(&self, _other: PrivateKeyBytes) -> Result<Self, Self::Err> {
+        // whatever it takes for tests to pass...
+        Ok(self.clone())
+    }
+}

crates/derive/keyfork-derive-util/src/request.rs

@@ -2,7 +2,9 @@
 #![allow(clippy::match_wildcard_for_single_variants)]
 
 use crate::{
-    extended_key::private_key::Error as XPrvError, DerivationPath, ExtendedPrivateKey, PrivateKey,
+    extended_key::private_key::Error as XPrvError,
+    private_key::{PrivateKey, TestPrivateKey},
+    DerivationPath, ExtendedPrivateKey,
 };
 use keyfork_mnemonic_util::{Mnemonic, MnemonicGenerationError};
 use serde::{Deserialize, Serialize};
@@ -30,11 +32,14 @@ pub type Result<T, E = DerivationError> = std::result::Result<T, E>;
 /// The algorithm to derive a key for. The choice of algorithm will result in a different resulting
 /// derivation.
 #[derive(Serialize, Deserialize, Clone, Debug)]
+#[non_exhaustive]
 pub enum DerivationAlgorithm {
     #[allow(missing_docs)]
     Ed25519,
     #[allow(missing_docs)]
     Secp256k1,
+    #[doc(hidden)]
+    Internal,
 }
 
 impl DerivationAlgorithm {
@@ -42,7 +47,7 @@ impl DerivationAlgorithm {
     ///
     /// # Errors
     /// The method may error if the derivation fails or if the algorithm is not supported.
-    pub fn derive(&self, seed: Vec<u8>, path: &DerivationPath) -> Result<DerivationResponse> {
+    fn derive(&self, seed: Vec<u8>, path: &DerivationPath) -> Result<DerivationResponse> {
         match self {
             #[cfg(feature = "ed25519")]
             Self::Ed25519 => {
@@ -62,6 +67,14 @@ impl DerivationAlgorithm {
                     &derived_key,
                 ))
             }
+            Self::Internal => {
+                let key = ExtendedPrivateKey::<TestPrivateKey>::new(seed)?;
+                let derived_key = key.derive_path(path)?;
+                Ok(DerivationResponse::with_algo_and_xprv(
+                    self.clone(),
+                    &derived_key,
+                ))
+            }
             #[allow(unreachable_patterns)]
             _ => Err(DerivationError::Algorithm),
         }
@@ -89,6 +102,23 @@ pub struct DerivationRequest {
 
 impl DerivationRequest {
     /// Create a new derivation request.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   request::*,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// #   private_key::TestPrivateKey as PrivateKey,
+    /// # };
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let algo: DerivationAlgorithm = //
+    /// #   DerivationAlgorithm::Internal;
+    /// let path: DerivationPath = //
+    /// #   DerivationPath::default();
+    /// let request = DerivationRequest::new(algo, &path);
+    /// # Ok(())
+    /// # }
     pub fn new(algorithm: DerivationAlgorithm, path: &DerivationPath) -> Self {
         Self {
             algorithm,
@@ -97,6 +127,24 @@ impl DerivationRequest {
     }
 
     /// Return the path of the derivation request.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   request::*,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// #   private_key::TestPrivateKey as PrivateKey,
+    /// # };
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let algo: DerivationAlgorithm = //
+    /// #   DerivationAlgorithm::Internal;
+    /// let path: DerivationPath = //
+    /// #   DerivationPath::default();
+    /// let request = DerivationRequest::new(algo, &path);
+    /// assert_eq!(&path, request.path());
+    /// # Ok(())
+    /// # }
     pub fn path(&self) -> &DerivationPath {
         &self.path
     }
@@ -105,6 +153,29 @@ impl DerivationRequest {
     ///
     /// # Errors
     /// The method may error if the derivation fails or if the algorithm is not supported.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   request::*,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// #   private_key::TestPrivateKey as PrivateKey,
+    /// # };
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let mnemonic: keyfork_mnemonic_util::Mnemonic = //
+    /// #   keyfork_mnemonic_util::Mnemonic::from_entropy(
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
+    /// #   Default::default(),
+    /// #   )?;
+    /// let algo: DerivationAlgorithm = //
+    /// #   DerivationAlgorithm::Internal;
+    /// let path: DerivationPath = //
+    /// #   DerivationPath::default();
+    /// let request = DerivationRequest::new(algo, &path);
+    /// let response = request.derive_with_mnemonic(&mnemonic)?;
+    /// # Ok(())
+    /// # }
     pub fn derive_with_mnemonic(&self, mnemonic: &Mnemonic) -> Result<DerivationResponse> {
         // TODO: passphrase support and/or store passphrase within mnemonic
         self.derive_with_master_seed(mnemonic.seed(None)?)
@@ -114,6 +185,26 @@ impl DerivationRequest {
     ///
     /// # Errors
     /// The method may error if the derivation fails or if the algorithm is not supported.
+    ///
+    /// # Examples
+    /// ```rust
+    /// # use keyfork_derive_util::{
+    /// #   *,
+    /// #   request::*,
+    /// #   public_key::TestPublicKey as PublicKey,
+    /// #   private_key::TestPrivateKey as PrivateKey,
+    /// # };
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let seed: &[u8; 64] = //
+    /// #   b"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+    /// let algo: DerivationAlgorithm = //
+    /// #   DerivationAlgorithm::Internal;
+    /// let path: DerivationPath = //
+    /// #   DerivationPath::default();
+    /// let request = DerivationRequest::new(algo, &path);
+    /// let response = request.derive_with_master_seed(seed.to_vec())?;
+    /// # Ok(())
+    /// # }
     pub fn derive_with_master_seed(&self, seed: Vec<u8>) -> Result<DerivationResponse> {
         self.algorithm.derive(seed, &self.path)
     }
@@ -137,7 +228,7 @@ pub struct DerivationResponse {
 
 impl DerivationResponse {
     /// Create a [`DerivationResponse`] with the given values.
-    pub fn with_algo_and_xprv<T: PrivateKey + Clone>(
+    fn with_algo_and_xprv<T: PrivateKey + Clone>(
         algorithm: DerivationAlgorithm,
         xprv: &ExtendedPrivateKey<T>,
     ) -> Self {