当AesManaged.FeedbackSize = 128

Question

我希望明确设置加密参数（从.NET 4.7默认值中读取），以便在以后的框架版本实现不同的默认值时避免以后的解密困难。

为什么在手动设置反馈FeedbackSize之后，FeedbackSizeValue不会改变？

AesManaged aes = new AesManaged();
aes.Mode = CipherMode.CBC;
aes.KeySize = 256;
aes.Padding = PaddingMode.PKCS7;
aes.BlockSize = 128;
aes.FeedbackSize = aes.BlockSize;

这是aes对象，请参阅FeedbackSizeValue 8

-       aes {System.Security.Cryptography.AesManaged}   System.Security.Cryptography.AesManaged

-       aes {System.Security.Cryptography.AesManaged}   System.Security.Cryptography.AesManaged
        BlockSize   128 int
        BlockSizeValue  128 int
        FeedbackSize    128 int
        FeedbackSizeValue   8   int
+       IV  {byte[16]}  byte[]
        IVValue null    byte[]
+       Key {byte[32]}  byte[]
        KeySize 256 int
        KeySizeValue    256 int
        KeyValue    null    byte[]
+       LegalBlockSizes {System.Security.Cryptography.KeySizes[1]}  System.Security.Cryptography.KeySizes[]
+       LegalBlockSizesValue    {System.Security.Cryptography.KeySizes[1]}  System.Security.Cryptography.KeySizes[]
+       LegalKeySizes   {System.Security.Cryptography.KeySizes[1]}  System.Security.Cryptography.KeySizes[]
+       LegalKeySizesValue  {System.Security.Cryptography.KeySizes[1]}  System.Security.Cryptography.KeySizes[]
        Mode    CBC System.Security.Cryptography.CipherMode
        ModeValue   CBC System.Security.Cryptography.CipherMode
        Padding PKCS7   System.Security.Cryptography.PaddingMode
        PaddingValue    PKCS7   System.Security.Cryptography.PaddingMode
+       m_rijndael  {System.Security.Cryptography.RijndaelManaged}  System.Security.Cryptography.RijndaelManaged
+       Static members      

Answer 1

CBC模式没有反馈大小。见CBC mode：

来自维基百科的图形

此外，无需指定块大小（aes.BlockSize = 128;），AES只有一个块大小。 Rijndael支持几种块大小，有必要指定128位的块大小，基本上是AES。虽然许多Rijndael实现默认为128位的块大小，但完全指定参数总是更好。