crypto: add OriginSigningKey for the origin key ceremony

README.md

@@ -16,7 +16,7 @@ A site built with Entangled is not a web application. It is a set of signed JSON
 
 - [`entangled-core`](./entangled-core): the protocol core library.
 
-Current crate version: `0.9.0`.
+Current crate version: `0.10.0`.
 
 Implemented in `entangled-core`:
 

entangled-core/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "entangled-core"
-version = "0.9.0"
+version = "0.10.0"
 edition = "2021"
 rust-version = "1.88"
 license = "MIT OR Apache-2.0"

entangled-core/src/crypto/ed25519.rs

@@ -215,6 +215,16 @@ pub struct PublisherSigningKey(SigningKey);
 /// not interconvertible with it at the public API level.
 pub struct RuntimeSigningKey(SigningKey);
 
+/// Origin key. Binds the manifest to a Tor v3 carrier address.
+///
+/// `K_origin` (§05, §06) is never used to sign Entangled documents in v1.0:
+/// it exists only so the onion address derives from it and the manifest's
+/// `origin.origin_pubkey` can be checked against the address. This newtype
+/// therefore exposes seed-based construction and public-key derivation but,
+/// unlike [`PublisherSigningKey`] and [`RuntimeSigningKey`], no signing
+/// method. A publisher holds the origin seed to derive its onion address.
+pub struct OriginSigningKey(SigningKey);
+
 impl PublisherSigningKey {
     /// Generate a fresh publisher keypair from OS entropy.
     ///
@@ -276,6 +286,29 @@ impl RuntimeSigningKey {
     }
 }
 
+impl OriginSigningKey {
+    /// Generate a fresh origin keypair from OS entropy.
+    ///
+    /// Test-only: gated behind `#[cfg(test)]` and the `test-utils` feature.
+    #[cfg(any(test, feature = "test-utils"))]
+    pub fn generate() -> Self {
+        Self(SigningKey::generate())
+    }
+
+    /// Build an [`OriginSigningKey`] from a 32-byte seed
+    /// (the RFC 8032 secret key).
+    pub fn from_seed(seed: &[u8; 32]) -> Self {
+        Self(SigningKey::from_seed(seed))
+    }
+
+    /// Return the [`OriginPubkey`] derived from this key. Combine with
+    /// [`crate::types::manifest::OnionAddress::from_origin_pubkey`] to obtain
+    /// the carrier address.
+    pub fn verifying_key(&self) -> OriginPubkey {
+        self.0.verifying_key().to_origin_pubkey()
+    }
+}
+
 impl VerifyingKey {
     /// Parse a [`PublisherPubkey`] into a [`VerifyingKey`].
     ///

entangled-core/src/crypto/mod.rs

@@ -9,8 +9,8 @@ pub mod signing;
 
 pub use ed25519::{
     validate_origin_pubkey_strict, validate_pubkey_strict, validate_publisher_pubkey_strict,
-    validate_runtime_pubkey_strict, CryptoError, PublisherSigningKey, RuntimeSigningKey,
-    VerifyingKey,
+    validate_runtime_pubkey_strict, CryptoError, OriginSigningKey, PublisherSigningKey,
+    RuntimeSigningKey, VerifyingKey,
 };
 pub use pip::{derive_pip, pip_to_pubkey, PipError};
 pub use sha256::{sha256, sha256_base64url, sha256_image, sha256_request};

entangled-core/tests/tor/address_decode.rs

@@ -1,7 +1,7 @@
 //! `OnionAddress::decode` and `verify_strict` exercises.
 
 use data_encoding::BASE32;
-use entangled_core::crypto::PublisherSigningKey;
+use entangled_core::crypto::{OriginSigningKey, PublisherSigningKey};
 use entangled_core::tor::TorError;
 use entangled_core::types::keys::OriginPubkey;
 use entangled_core::types::manifest::OnionAddress;
@@ -157,6 +157,26 @@ fn from_origin_pubkey_corpus_fixture() {
     );
 }
 
+/// End-to-end origin ceremony against the corpus fixture: the origin seed
+/// `ENTANGLED-v1.0-origin-test00001\0` derives, through
+/// `OriginSigningKey -> OriginPubkey -> from_origin_pubkey`, to the same
+/// public key and onion address the corpus records.
+#[test]
+fn origin_seed_to_onion_corpus_fixture() {
+    let seed: [u8; 32] = *b"ENTANGLED-v1.0-origin-test00001\0";
+    let origin_key = OriginSigningKey::from_seed(&seed);
+    let pubkey = origin_key.verifying_key();
+    assert_eq!(
+        pubkey.to_string(),
+        "Gp8y4JM7Qlkn8JXkJAOW8s3MSkkQNGHGC1c7-AK6Wpo"
+    );
+    let addr = OnionAddress::from_origin_pubkey(&pubkey);
+    assert_eq!(
+        addr.as_str(),
+        "dkptfyethnbfsj7qsxscia4w6lg4yssjca2gdrqlk457qav2lkna4xqd.onion"
+    );
+}
+
 /// Public test vector: DuckDuckGo's onion service v3 address. We can't verify
 /// "the right pubkey" without their key material, but the checksum and version
 /// byte must verify under our decoder for the implementation to be