diff --git a/Controller/CryptoSettingViewModel.swift b/Controller/CryptoSettingViewModel.swift
index 0297d0c..d0197e7 100644
--- a/Controller/CryptoSettingViewModel.swift
+++ b/Controller/CryptoSettingViewModel.swift
@@ -135,7 +135,7 @@ class CryptoSettingViewModel: ViewModel, ViewModelType {
         return Output(
             initial: Driver.just((
                 algorithmList: [Algorithm.aes128, Algorithm.aes192, Algorithm.aes256],
-                modeList: ["CBC", "ECB", "GCM"],
+                modeList: ["CBC", "ECB", /* "GCM" */],  // GCM 还没准备好示例代码，暂时禁用
                 paddingList: ["pkcs7"],
                 initialFields: dependencies.settingFieldRelay.value
             )),
diff --git a/Model/Algorithm.swift b/Model/Algorithm.swift
index 585ef31..1a3cde0 100644
--- a/Model/Algorithm.swift
+++ b/Model/Algorithm.swift
@@ -67,13 +67,10 @@ struct AESCryptoModel {
 
         var iv = ""
         if ["CBC", "GCM"].contains(cryptoFields.mode) {
-            var expectIVLength = 0
-            if cryptoFields.mode == "CBC" {
-                expectIVLength = 16
-            }
-            else if cryptoFields.mode == "GCM" {
-                expectIVLength = 12
-            }
+            let expectIVLength = [
+                "CBC": 16,
+                "GCM": 12
+            ][cryptoFields.mode] ?? 0
 
             if let ivField = cryptoFields.iv, ivField.count == expectIVLength {
                 iv = ivField