Add support for key create --type aes256.

CHANGELOG.md

@@ -1,5 +1,19 @@
 # History
 
+## Unreleased - TBD
+
+### Added
+
+- `key create --type aes256` generates a symmetric AES-256 key-encryption key
+  (KEK): 32 random bytes carried as a `Multikey` `secretKeyMultibase` (the
+  AES-256 multicodec header `0xa2 0x01` followed by the raw key bytes),
+  identified by a `urn:kek:sha256:` id derived from the SHA-256 digest of the
+  raw key bytes. This is the form Wallet Attached Storage servers accept for
+  their at-rest key-encryption-key configuration. Generation is always fresh and
+  random, so `--with-seed` and `SECRET_KEY_SEED` are not supported for this
+  type. `key show` prints only the safe `id` and `type` for a saved KEK, never
+  the secret material.
+
 ## 0.12.0 - 2026-07-09
 
 ### Changed

README.md

@@ -166,7 +166,7 @@ SECRET_KEY_SEED=z1AXVyT6G1Qk3E9cMPkDYY6wVRpZjVGWAZ3TfrAgFZkX6bv ./di key create
 ```
 
 Specify an explicit key type with `--type` (defaults to `ed25519`; supported:
-`ed25519`, `ecdsa`, `x25519`, `hmac`):
+`ed25519`, `ecdsa`, `x25519`, `hmac`, `aes256`):
 
 ```
 SECRET_KEY_SEED=z1Aaj5A4UCsd... ./di key create --type ed25519
@@ -244,6 +244,32 @@ half), identified by a random `urn:uuid:` id:
 HMAC key generation is non-deterministic, so `--with-seed` and `SECRET_KEY_SEED`
 are not supported with `--type hmac`.
 
+Generate a symmetric AES-256 key-encryption key (KEK) -- 32 random bytes carried
+as a Multikey `secretKeyMultibase` -- with `--type aes256`:
+
+```
+./di key create --type aes256
+```
+
+It is serialized as a `Multikey` with the secret carried as a base58btc
+`secretKeyMultibase` (the AES-256 multicodec header `0xa2 0x01` followed by the
+32 raw key bytes, no public half), identified by a `urn:kek:sha256:` id derived
+from the SHA-256 digest of the raw key bytes:
+
+```json
+{
+  "id": "urn:kek:sha256:...",
+  "type": "Multikey",
+  "secretKeyMultibase": "z..."
+}
+```
+
+This is the form Wallet Attached Storage servers accept for their at-rest
+key-encryption-key configuration (`KMS_RECORD_KEK` / `KMS_RECORD_KEKS`), where
+each KEK is identified by the same derived `urn:kek:sha256:` id. Generation is
+always fresh and random, so `--with-seed` and `SECRET_KEY_SEED` are not
+supported with `--type aes256`.
+
 Save the key to local wallet storage (`~/.config/did-cli-wallet/keys/` by
 default, or
 `$WALLET_DIR/keys/` if set) with `--save`. A `.meta.json` metadata sidecar is

package.json

@@ -26,7 +26,7 @@
   "dependencies": {
     "@digitalcredentials/bnid": "^5.0.0",
     "@digitalcredentials/issuer-registry-client": "^4.0.0",
-    "@interop/data-integrity-core": "^8.1.0",
+    "@interop/data-integrity-core": "^8.2.0",
     "@interop/data-integrity-proof": "^3.4.1",
     "@interop/did-io": "^4.0.6",
     "@interop/did-method-key": "^7.3.3",
@@ -36,14 +36,14 @@
     "@interop/ecdsa-signature": "2.0.4",
     "@interop/ed25519-signature": "^7.1.3",
     "@interop/ed25519-verification-key": "^8.0.2",
-    "@interop/edv-client": "^17.5.0",
+    "@interop/edv-client": "^17.6.1",
     "@interop/ezcap": "^7.3.2",
-    "@interop/minimal-cipher": "^7.5.0",
+    "@interop/minimal-cipher": "^7.6.1",
     "@interop/security-document-loader": "^9.4.1",
     "@interop/vc": "^11.0.5",
     "@interop/verifier-core": "^3.3.1",
-    "@interop/was-client": "^0.13.3",
-    "@interop/x25519-key-agreement-key": "^5.1.1",
+    "@interop/was-client": "^0.14.5",
+    "@interop/x25519-key-agreement-key": "^5.2.0",
     "@interop/zcap": "^11.0.4",
     "@scure/base": "^2.2.0",
     "commander": "^15.0.0"