doc(bls-encrypt): better comment on G2/G1 points usage

Author: Ansonhkg

packages/crypto/src/lib/crypto.ts

@@ -104,6 +104,7 @@ export const unloadModules = () => {
 
 /**
  * Encrypt data with a BLS public key.
+ * We are using G1 for encryption and G2 for signatures
  *
  * @param publicKey hex-encoded string of the BLS public key to encrypt with
  * @param data Uint8Array of the data to encrypt
@@ -114,12 +115,35 @@ export const encrypt = (
   publicKey: string,
   data: Uint8Array,
   identity: Uint8Array
-): string => {
-  return blsSdk.encrypt(
-    publicKey,
-    uint8arrayToString(data, 'base64'),
-    uint8arrayToString(identity, 'base64')
-  );
+): Promise<string> => {
+
+  const publicKey = Buffer.from(publicKeyHex, 'hex');
+
+  /**
+ * Our system uses BLS12-381 on the G1 curve for encryption.
+ * However, on the SDK side (this function), we expect the public key
+ * to use the G2 curve for signature purposes, hence the switch on public key length.
+ *
+ * The G2 curve, `Bls12381G2`, is typically associated with signature generation/verification,
+ * while G1 is associated with encryption. Here, the length of the public key determines how 
+ * we handle the encryption and the format of the returned encrypted message.
+ */
+  switch (publicKeyHex.replace('0x', '').length) {
+
+    /**
+     * @deprecated - not sure if this is still used/needed
+     */
+    case 218:
+      return Buffer.from(
+        await blsEncrypt('Bls12381G2', publicKey, message, identity)
+      ).toString('hex');
+    case 96:
+      return Buffer.from(
+        await blsEncrypt('Bls12381G2', publicKey, message, identity)
+      ).toString('base64');
+    default:
+      return '';
+  }
 };
 
 /**