Allow 32-byte secret keys (secret bytes only, no public bytes).

CHANGELOG.md

@@ -1,5 +1,13 @@
 # @digitalbazaar/ed25519-multikey ChangeLog
 
+## 1.2.0 - 2024-08-dd
+
+### Added
+- Allow 32-byte or 64-byte secret key values. The actual secret part of
+  the secret key is the first 32 bytes, but some implementations concatenate
+  the public key (an additional 32 bytes) onto the "secret key bytes"; this
+  feature allows either to be used.
+
 ## 1.1.0 - 2024-03-17
 
 ### Added

lib/ed25519.js

@@ -113,7 +113,8 @@ function _secretKeyDerEncode({secretKeyBytes, seedBytes}) {
   if(!seedBytes) {
     assertKeyBytes({
       bytes: secretKeyBytes,
-      expectedLength: 64
+      // allow 32 bytes or 64 bytes
+      expectedLength: secretKeyBytes.length === 32 ? 32 : 64
     });
   }
   let p;