ModernKeePassLib implements HMAC correctly

Blake2b also implemented, but not tested
ModernKeePass app better implements focus on database password box (but still not working correctly)

ModernKeePassLib/Cryptography/Cipher/ChaCha20Engine.cs

@@ -122,7 +122,7 @@ namespace ModernKeePassLib.Cryptography.Cipher
 					m_c.Dispose();
 					m_c = null;
 
-					//m_sBase.Close();
+					m_sBase.Dispose();
 					m_sBase = null;
 				}
 

ModernKeePassLib/Cryptography/Cipher/CipherPool.cs

@@ -22,7 +22,6 @@ using System.Collections.Generic;
 using System.Text;
 using System.IO;
 using System.Diagnostics;
-using System.Security;
 
 namespace ModernKeePassLib.Cryptography.Cipher
 {

ModernKeePassLib/Cryptography/Cipher/StandardAesEngine.cs

@@ -18,7 +18,10 @@
 */
 
 using System;
+using System.Collections.Generic;
+using System.Text;
 using System.IO;
+using System.Security;
 using System.Diagnostics;
 #if ModernKeePassLib
 using ModernKeePassLib.Resources;