diff --git a/src/main/kotlin/cn/tursom/core/encrypt/RSA.kt b/src/main/kotlin/cn/tursom/core/encrypt/RSA.kt
index 8205fa5..bb44d57 100644
--- a/src/main/kotlin/cn/tursom/core/encrypt/RSA.kt
+++ b/src/main/kotlin/cn/tursom/core/encrypt/RSA.kt
@@ -19,6 +19,14 @@ class RSA(val publicKey: RSAPublicKey, val privateKey: RSAPrivateKey? = null) :
   val decryptMaxLen = keySize / 8
   val encryptMaxLen = decryptMaxLen - 11
 
+  val public by lazy {
+    if (privateKey == null) {
+      this
+    } else {
+      RSA(publicKey)
+    }
+  }
+
   private val encryptCipher = Cipher.getInstance("RSA")!!
   private val decryptCipher = Cipher.getInstance("RSA")!!