refactor(hub): the transport holds an identity, never a private key

Two public keys, sign() and shared(); the apps take transport.signFn. What
holds the keys (this page, or the desktop main process) is the identity's
business alone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 10 insertions, 16 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/transport-devices.js b/packages/meshbay-hub/src/meshbay_hub/static/transport-devices.js
index 199b6a2..f17b1b6 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/transport-devices.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/transport-devices.js
@@ -94,7 +94,7 @@ extendTransport(class {
    * this node sees this account (and not at all in an open-join group).
    */
   async joinGroup(userId, groupId, code) {
-    if (!this._sessionKeys || !this._sessionKeys.skEdB64 || !this._sessionKeys.skXB64) {
+    if (!this._identity) {
       throw new Error('Identity keys unavailable in this browser — sign in again');
     }
     if (!this._nonceNode || !this.nodePk) {
@@ -102,13 +102,12 @@ extendTransport(class {
     }
 
     const C = window.MeshBayCrypto;
-    const pkEdB64 = await _pkEdFromSk(this._sessionKeys.skEdB64);
-    const pkXB64 = await _pkFromSk(this._sessionKeys.skXB64);
+    const { pkEdB64, pkXB64 } = this._identity;
     const ts = Math.floor(Date.now() / 1000);
 
     const transcript = C.joinTranscript(
       this.nodePk, groupId || '', userId, pkEdB64, pkXB64, this._nonceNode, ts);
-    const sig = await window.MeshBayKeys.signBytes(this._sessionKeys.skEdB64, transcript);
+    const sig = await this._identity.sign(transcript);
 
     const resp = await this._sendAndWait({
       type: 'join_request',
@@ -133,9 +132,8 @@ extendTransport(class {
 
     // Unwrap with our own secret key — the node wrapped for the public key we
     // just proved we hold, so nobody else can open this.
-    const skXRaw = Uint8Array.from(atob(this._sessionKeys.skXB64), c => c.charCodeAt(0));
     const myPkX = Uint8Array.from(atob(pkXB64), c => c.charCodeAt(0));
-    const gekRaw = await C.unwrapGEK(resp, skXRaw, myPkX);
+    const gekRaw = await C.unwrapGEK(resp, (pk) => this._identity.shared(pk), myPkX);
     this._gekRaw = gekRaw;
     // What the node's roster says this identity is, which is not what the hub
     // says: `operator` here means this browser's key was paired with the node,
@@ -154,15 +152,14 @@ extendTransport(class {
    * device cannot be handed a substituted key and sign for it by mistake.
    */
   async requestDeviceAdd(userId) {
-    if (!this._sessionKeys || !this._sessionKeys.skEdB64) {
+    if (!this._identity) {
       throw new Error('Identity keys unavailable in this browser — sign in again');
     }
     if (!this._nonceNode || !this.nodePk) {
       throw new Error('Handshake incomplete — reconnect and retry');
     }
     const C = window.MeshBayCrypto;
-    const pkEdB64 = await _pkEdFromSk(this._sessionKeys.skEdB64);
-    const pkXB64 = await _pkFromSk(this._sessionKeys.skXB64);
+    const { pkEdB64, pkXB64 } = this._identity;
 
     // 40 bits from the platform CSPRNG, in the same alphabet as a pairing code
     // so it reads and types the same way.
@@ -176,8 +173,7 @@ extendTransport(class {
     const ts = Math.floor(Date.now() / 1000);
     const transcript = C.deviceRequestTranscript(
       this.nodePk, userId, pkEdB64, pkXB64, codeHash, this._nonceNode, ts);
-    const sig = await window.MeshBayKeys.signBytes(
-      this._sessionKeys.skEdB64, transcript);
+    const sig = await this._identity.sign(transcript);
 
     const resp = await this._sendAndWait({
       type: 'device_add_request', v: '0.1',
@@ -196,7 +192,7 @@ extendTransport(class {
    * nothing to sign and nothing for a person to misread.
    */
   async approveDevice(userId, code) {
-    if (!this._sessionKeys || !this._sessionKeys.skEdB64) {
+    if (!this._identity) {
       throw new Error('Identity keys unavailable in this browser — sign in again');
     }
     if (!this._nonceNode || !this.nodePk) {
@@ -231,8 +227,7 @@ extendTransport(class {
     const ts = Math.floor(Date.now() / 1000);
     const transcript = C.deviceAddTranscript(
       this.nodePk, userId, pkEdB64, pkXB64, this._nonceNode, ts);
-    const sig = await window.MeshBayKeys.signBytes(
-      this._sessionKeys.skEdB64, transcript);
+    const sig = await this._identity.sign(transcript);
     const resp = await this._sendAndWait({
       type: 'device_add', v: '0.1',
       pk_ed25519: pkEdB64, pk_x25519: pkXB64, code_hash: codeHash, ts, sig,
@@ -253,8 +248,7 @@ extendTransport(class {
     const ts = Math.floor(Date.now() / 1000);
     const transcript = C.deviceAddTranscript(
       this.nodePk, userId, pkEdB64, pkXB64, this._nonceNode, ts);
-    const sig = await window.MeshBayKeys.signBytes(
-      this._sessionKeys.skEdB64, transcript);
+    const sig = await this._identity.sign(transcript);
     const resp = await this._sendAndWait({
       type: 'device_revoke', v: '0.1', pk_ed25519: pkEdB64, ts, sig,
     });