refactor(crypto): share byte-compatible Ed25519 signing

AGENTS.md

@@ -117,6 +117,12 @@ checks and the path validator used after an explicit download action. That
 validator accepts release assets from `NDDev-OpenNetwork/nremote` and no other
 origin; there is no scheduler, release lookup, or background download.
 
+Authentication signing uses `crypto_sign.rs`, byte-identical to the server's
+copy at the coordinated migration point. It preserves 64-byte
+`seed || public key` storage and `signature || message` wire payloads; the RFC
+8032 vector is the compatibility gate. `sodiumoxide` remains for unrelated
+`box_` and XSalsa20-Poly1305 `secretbox` protocol operations.
+
 ## Verification
 
 ```bash

NOTICE

@@ -53,6 +53,11 @@ Modified by NDDev beginning 2026-09-02. Changes so far:
   * The wire protocol shared with nremote-server is pinned by digest and
     checked on both sides by scripts/check_protocol_parity.py.
 
+  * Authentication signing is moved from an unmaintained wrapper to
+    `ed25519-dalek`. Persisted device keypairs and signed server messages retain
+    their existing byte layouts, verified against the RFC 8032 Ed25519 test
+    vector; malformed stored keypairs are rejected before use.
+
 The rendezvous protocol is unchanged. This client interoperates with servers
 built from the prior work, and nremote-server interoperates with clients built
 from it, which is what makes an incremental migration possible.

libs/hbb_common/Cargo.toml

@@ -28,6 +28,7 @@ zstd = "0.13"
 anyhow = "1.0"
 futures-util = "0.3"
 directories-next = "2.0"
+ed25519-dalek = "3.0"
 rand = "0.10"
 serde_derive = "1.0"
 serde = "1.0"

libs/hbb_common/src/config.rs

@@ -9,6 +9,7 @@ use std::{
     time::{Duration, Instant, SystemTime},
 };
 
+use crate::crypto_sign as sign;
 use anyhow::{anyhow, Result};
 use bytes::Bytes;
 use rand::RngExt;
@@ -17,7 +18,6 @@ use serde as de;
 use serde_derive::{Deserialize, Serialize};
 use serde_json;
 use sodiumoxide::base64;
-use sodiumoxide::crypto::sign;
 
 mod permanent_password;