diff --git a/phpseclib/Crypt/ChaCha20.php b/phpseclib/Crypt/ChaCha20.php
index 0f9e90c1..6e1d3919 100644
--- a/phpseclib/Crypt/ChaCha20.php
+++ b/phpseclib/Crypt/ChaCha20.php
@@ -186,7 +186,7 @@ class ChaCha20 extends Salsa20
      *
      * @param string $nonce
      */
-     public function setNonce($nonce)
+    public function setNonce($nonce)
     {
         if (!is_string($nonce)) {
             throw new \UnexpectedValueException('The nonce should be a string');
@@ -238,7 +238,7 @@ class ChaCha20 extends Salsa20
 
         $this->enbuffer = $this->debuffer = ['ciphertext' => '', 'counter' => $this->counter];
 
-        $this->changed = false;
+        $this->changed = $this->nonIVChanged = false;
 
         if ($this->nonce === false) {
             throw new InsufficientSetupException('No nonce has been defined');
diff --git a/phpseclib/Crypt/Common/SymmetricKey.php b/phpseclib/Crypt/Common/SymmetricKey.php
index 28041d3d..8c16a784 100644
--- a/phpseclib/Crypt/Common/SymmetricKey.php
+++ b/phpseclib/Crypt/Common/SymmetricKey.php
@@ -351,6 +351,15 @@ abstract class SymmetricKey
      */
     protected $changed = true;
 
+    /**
+     * Does Eval engie need to be (re)initialized?
+     *
+     * @see self::setup()
+     * @var bool
+     * @access private
+     */
+    protected $nonIVChanged = true;
+
     /**
      * Padding status
      *
@@ -742,7 +751,6 @@ abstract class SymmetricKey
         }
 
         $this->nonce = $nonce;
-        $this->changed = true;
         $this->setEngine();
     }
 
@@ -859,7 +867,6 @@ abstract class SymmetricKey
 
         $this->key = $key;
         $this->key_length = strlen($key);
-        $this->changed = true;
         $this->setEngine();
     }
 
@@ -2104,7 +2111,6 @@ abstract class SymmetricKey
         }
 
         $this->continuousBuffer = false;
-        $this->changed = true;
 
         $this->setEngine();
     }
@@ -2271,7 +2277,7 @@ abstract class SymmetricKey
             }
         }
 
-        $this->changed = true;
+        $this->changed = $this->nonIVChanged = true;
     }
 
     /**
@@ -2404,9 +2410,13 @@ abstract class SymmetricKey
                 $this->setupKey();
                 break;
             case self::ENGINE_EVAL:
-                $this->setupKey();
-                $this->setupInlineCrypt();
+                if ($this->nonIVChanged) {
+                    $this->setupKey();
+                    $this->setupInlineCrypt();
+                }
         }
+
+        $this->nonIVChanged = false;
     }
 
     /**
diff --git a/phpseclib/Crypt/RC2.php b/phpseclib/Crypt/RC2.php
index 317d4380..9f4acfce 100644
--- a/phpseclib/Crypt/RC2.php
+++ b/phpseclib/Crypt/RC2.php
@@ -395,7 +395,7 @@ class RC2 extends BlockCipher
 
         $this->key = call_user_func_array('pack', $l);
         $this->key_length = strlen($this->key);
-        $this->changed = true;
+        $this->changed = $this->nonIVChanged = true;
         $this->setEngine();
     }
 
diff --git a/phpseclib/Crypt/RC4.php b/phpseclib/Crypt/RC4.php
index 9922a268..c658144a 100644
--- a/phpseclib/Crypt/RC4.php
+++ b/phpseclib/Crypt/RC4.php
@@ -310,7 +310,6 @@ class RC4 extends StreamCipher
     {
         if ($this->changed) {
             $this->setup();
-            $this->changed = false;
         }
 
         $stream = &$this->stream[$mode];
diff --git a/phpseclib/Crypt/Rijndael.php b/phpseclib/Crypt/Rijndael.php
index 58aa80e0..0fe13c90 100644
--- a/phpseclib/Crypt/Rijndael.php
+++ b/phpseclib/Crypt/Rijndael.php
@@ -267,7 +267,7 @@ class Rijndael extends BlockCipher
 
         $this->Nb = $length >> 5;
         $this->block_size = $length >> 3;
-        $this->changed = true;
+        $this->changed = $this->nonIVChanged = true;
         $this->setEngine();
     }
 
diff --git a/phpseclib/Crypt/Salsa20.php b/phpseclib/Crypt/Salsa20.php
index 0d59c808..7f51a93c 100644
--- a/phpseclib/Crypt/Salsa20.php
+++ b/phpseclib/Crypt/Salsa20.php
@@ -225,7 +225,7 @@ class Salsa20 extends StreamCipher
 
         $this->enbuffer = $this->debuffer = ['ciphertext' => '', 'counter' => $this->counter];
 
-        $this->changed = false;
+        $this->changed = $this->nonIVChanged = false;
 
         if ($this->nonce === false) {
             throw new InsufficientSetupException('No nonce has been defined');
diff --git a/phpseclib/Crypt/TripleDES.php b/phpseclib/Crypt/TripleDES.php
index aa1f5216..f530758a 100644
--- a/phpseclib/Crypt/TripleDES.php
+++ b/phpseclib/Crypt/TripleDES.php
@@ -271,7 +271,7 @@ class TripleDES extends DES
         // copied from self::setKey()
         $this->key = $key;
         $this->key_length = strlen($key);
-        $this->changed = true;
+        $this->changed = $this->nonIVChanged = true;
         $this->setEngine();
 
         if ($this->mode_3cbc) {