fix(open from existing): create encrypted core from unencrypted core

same logic in core.session() added to core._openFromExisting with one
difference; new core will override existing.encryption

Closes hypercore-protocol/corestore-next#17

index.js

@@ -191,16 +191,7 @@ module.exports = class Hypercore extends EventEmitter {
 
     s._passCapabilities(this)
 
-    if (opts.encryptionKey) {
-      // Only override the block encryption if its either not already set or if
-      // the caller provided a different key.
-      if (
-        !s.encryption ||
-        !b4a.equals(s.encryption.key, opts.encryptionKey)
-      ) {
-        s.encryption = new BlockEncryption(opts.encryptionKey, s.key)
-      }
-    }
+    ensureEncryption(s, opts)
 
     this.sessions.push(s)
 
@@ -229,6 +220,8 @@ module.exports = class Hypercore extends EventEmitter {
     this.storage = from.storage
     this.replicator.findingPeers += this._findingPeers
 
+    ensureEncryption(this, opts)
+
     this.sessions.push(this)
   }
 
@@ -797,3 +790,12 @@ function preappend (blocks) {
     this.encryption.encrypt(offset + i, blocks[i], fork)
   }
 }
+
+function ensureEncryption (core, opts) {
+  if (!opts.encryptionKey) return
+  // Only override the block encryption if its either not already set or if
+  // the caller provided a different key.
+  if (!core.encryption || !b4a.equals(core.encryption.key, opts.encryptionKey)) {
+    core.encryption = new BlockEncryption(opts.encryptionKey, core.key)
+  }
+}

test/encryption.js

@@ -165,3 +165,16 @@ test('encrypted session on encrypted core, different keys', async function (t) {
   const encrypted = await a.get(0)
   t.absent(encrypted.includes('hello'))
 })
+
+test('encrypted core from existing unencrypted core', async function (t) {
+  const a = await create({ encryptionKey: Buffer.alloc(32, 'a') })
+  const b = await create({ from: a, encryptionKey })
+
+  t.alike(b.key, a.key)
+  t.alike(b.encryptionKey, encryptionKey)
+
+  await b.append(['hello'])
+
+  const unencrypted = await b.get(0)
+  t.alike(unencrypted, Buffer.from('hello'))
+})