Add SM2 algorithm support.

index.html

@@ -1457,6 +1457,16 @@ <h3>Multikey</h3>
 (`z`).
                   </td>
                 </tr>
+                <tr>
+                  <td>SM2 256-bit public key</td>
+                  <td>
+The encoding of an SM2 public key MUST start with the two-byte prefix
+`0x8624` (the varint expression of `0x1206`) followed by the 33-byte compressed
+public key data. The resulting 35-byte value MUST then be encoded using the
+base-58-btc alphabet, according to Section [[[#multibase-0]]], and then
+prepended with the base-58-btc Multibase header (`z`).
+                  </td>
+                </tr>
               </tbody>
             </table>
 
@@ -1511,6 +1521,16 @@ <h3>Multikey</h3>
 (`z`).
                   </td>
                 </tr>
+                <tr>
+                  <td>SM2 256-bit secret key</td>
+                  <td>
+The encoding of an SM2 secret key MUST start with the two-byte prefix
+`0x9026` (the varint expression of `0x1310`) followed by the 32-byte
+secret key data. The resulting 34-byte value MUST then be encoded using the
+base-58-btc alphabet, according to Section [[[#multibase-0]]], and then
+prepended with the base-58-btc Multibase header (`z`).
+                  </td>
+                </tr>
               </tbody>
 
             </table>
@@ -3841,6 +3861,16 @@ <h2>Multikey Examples</h2>
   "capabilityInvocation": [
     "https://controller.example/123#key-2"
   ]
+}
+          </pre>
+
+          <pre class="example nohighlight"
+            title="An SM2 public key encoded as a Multikey">
+{
+  "id": "https://multikey.example/issuer/123#key-0",
+  "type": "Multikey",
+  "controller": "https://multikey.example/issuer/123",
+  "publicKeyMultibase": "zEPJc1vCfbG2aoZn8f3U8ggYRL4ZFfF63ZA3qFSk81WJxnCQr"
 }
           </pre>
         </section>