Signed assertions

crates/stemedb-api/Cargo.toml

@@ -46,6 +46,7 @@ getrandom = "0.2"
 metrics = "0.23"
 metrics-exporter-prometheus = "0.15"
 dashmap = "6.0"
+ed25519-dalek = { version = "2.1", features = ["rand_core"] }
 
 [dev-dependencies]
 tempfile = "3"

crates/stemedb-api/src/handlers/stemedb_claims.rs

@@ -5,8 +5,10 @@
 
 use axum::{extract::{Path, State}, http::StatusCode, Json};
 use tracing::info;
+use ed25519_dalek::{SigningKey, Signer, VerifyingKey};
 
-use stemedb_core::types::{Assertion, LifecycleStage, ObjectValue};
+use stemedb_core::types::{Assertion, LifecycleStage, ObjectValue, SignatureEntry};
+use stemedb_core::signing::compute_content_hash_v2;
 use stemedb_ingest::worker::serialize_assertion;
 use stemedb_storage::{key_codec, KVStore};
 
@@ -16,6 +18,40 @@ use crate::{
     AppState,
 };
 
+// ============================================================================
+// Server Signing Key Generation
+
+/// Generate a deterministic server signing key from a seed.
+/// This ensures the same key is used across server restarts.
+fn get_server_signing_key() -> SigningKey {
+    // Use a fixed seed for deterministic key generation
+    // In production, this should be loaded from a config file or environment
+    let seed = [0x42u8; 32]; // Placeholder seed - replace with actual key management
+    SigningKey::from_bytes(&seed)
+}
+
+/// Sign an assertion with the server's key and add the signature.
+fn add_server_signature(assertion: &mut Assertion) {
+    let signing_key = get_server_signing_key();
+    let verifying_key: VerifyingKey = (&signing_key).into();
+
+    // Compute content hash for v2 signature
+    let content_hash = compute_content_hash_v2(assertion);
+
+    // Sign the content hash
+    let signature_bytes = signing_key.sign(&content_hash);
+
+    // Create signature entry
+    let sig_entry = SignatureEntry {
+        agent_id: verifying_key.to_bytes(),
+        signature: signature_bytes.to_bytes(),
+        timestamp: assertion.timestamp,
+        version: 2, // Use v2 (enterprise) signing
+    };
+
+    assertion.signatures.push(sig_entry);
+}
+
 // ============================================================================
 // Handlers
 // ============================================================================
@@ -39,7 +75,10 @@ pub async fn create_claim(
     info!(claim_id = %req.claim.id, concept_path = %req.claim.concept_path, "Creating claim in StemeDB");
 
     // Convert DTO to Assertion
-    let assertion = dto_to_assertion(&req.claim)?;
+    let mut assertion = dto_to_assertion(&req.claim)?;
+
+    // Add server signature to the assertion
+    add_server_signature(&mut assertion);
 
     // Serialize and append to WAL
     let payload = serialize_assertion(&assertion)