feat: PWD Base64

Cargo.toml

@@ -40,6 +40,7 @@ all-languages = [
 bitcoin = "0.32.4"
 bip39 = { version = "2.1.0", optional = true }
 sha3 = "0.10.8"
+base64 = "0.22.1"
 
 [[example]]
 name = "mnemonic"

README.md

@@ -17,7 +17,7 @@ This work is sponsored by [Bull Bitcoin](https://bullbitcoin.com) [<img
 - [x] [XPRV](https://github.com/bitcoin/bips/blob/master/bip-0085.mediawiki#user-content-XPRV)
 - [x] [HEX](https://github.com/bitcoin/bips/blob/master/bip-0085.mediawiki#hex)
 - [x] [DRNG](https://github.com/bitcoin/bips/blob/master/bip-0085.mediawiki#bip85-drng)
-- [ ] [PWD base64](https://github.com/bitcoin/bips/blob/master/bip-0085.mediawiki#user-content-PWD_BASE64)
+- [x] [PWD base64](https://github.com/bitcoin/bips/blob/master/bip-0085.mediawiki#user-content-PWD_BASE64)
 - [ ] [PWD base85](https://github.com/bitcoin/bips/blob/master/bip-0085.mediawiki#user-content-PWD_BASE85)
 - [ ] [RSA](https://github.com/bitcoin/bips/blob/master/bip-0085.mediawiki#user-content-RSA)
 - [ ] [RSA GPG](https://github.com/bitcoin/bips/blob/master/bip-0085.mediawiki#user-content-RSA_GPG)

src/lib.rs

@@ -28,13 +28,15 @@ pub mod drng;
 pub mod error;
 pub mod hex;
 pub mod mnemonic;
+pub mod pwd_base64;
 pub mod wif;
 pub mod xprv;
 
 pub use drng::*;
 pub use error::Error;
 pub use hex::*;
 pub use mnemonic::*;
+pub use pwd_base64::*;
 pub use wif::*;
 pub use xprv::*;
 

src/pwd_base64.rs

@@ -0,0 +1,32 @@
+use super::Error;
+use base64::prelude::BASE64_STANDARD;
+use base64::Engine;
+use bitcoin::bip32::{ChildNumber, DerivationPath};
+use bitcoin::{bip32::Xpriv, key::Secp256k1, secp256k1};
+
+/// The `length` can be from 20 to 86 and defines number of bytes derived.
+///
+/// See [specs](https://github.com/bitcoin/bips/blob/master/bip-0085.mediawiki#pwd-base64) for more info.
+pub fn to_pwd_base64<C: secp256k1::Signing>(
+    secp: &Secp256k1<C>,
+    root: &Xpriv,
+    length: u32,
+    index: u32,
+) -> Result<String, Error> {
+    const BIP85_PWD_B64_APPLICATION_NUMBER: ChildNumber = ChildNumber::Hardened { index: 707764 };
+    if length < 20 || length > 86 {
+        return Err(Error::InvalidLength(length));
+    }
+    if index >= 0x80000000 {
+        return Err(Error::InvalidIndex(index));
+    }
+    let path = DerivationPath::from(vec![
+        BIP85_PWD_B64_APPLICATION_NUMBER,
+        ChildNumber::from_hardened_idx(length).unwrap(),
+        ChildNumber::from_hardened_idx(index).unwrap(),
+    ]);
+    let data = crate::derive(secp, root, &path)?;
+    let mut pwd = BASE64_STANDARD.encode(data);
+    pwd.truncate(length.try_into().unwrap());
+    Ok(pwd)
+}

tests/pwd_base64_test.rs

@@ -0,0 +1,15 @@
+use std::str::FromStr;
+
+use bitcoin::{bip32::Xpriv, key::Secp256k1};
+
+#[test]
+fn test_pwd_base64() {
+    let root = Xpriv::from_str(
+        "xprv9s21ZrQH143K2LBWUUQRFXhucrQqBpKdRRxNVq2zBqsx8HVqFk2uYo8kmbaLLHRdqtQpUm98uKfu3vca1LqdGhUtyoFnCNkfmXRyPXLjbKb",
+    )
+    .unwrap();
+
+    let pwd_base64 = bip85_fork::to_pwd_base64(&Secp256k1::new(), &root, 21, 0).unwrap();
+    let expected = "dKLoepugzdVJvdL56ogNV";
+    assert_eq!(expected, pwd_base64);
+}