SymmetricAlgorithm 对称加密算法
SymmetricAlgorithm
Represents the abstract base class from which all implementations of symmetric algorithms must inherit.
- Derived
Rijndael Class 不推荐使用，建议使用Aes
Represents the base class from which all implementations of the Rijndael symmetric encryption algorithm must inherit.
Remarks
This algorithm supports key lengths of 128, 192, or 256 bits; defaulting to 256 bits. This algorithm supports block sizes of 128, 192, or 256 bits; defaulting to 128 bits (Aes-compatible).
The Rijndael class is the predecessor前辈 of the Aes algorithm. You should use the Aes algorithm instead of Rijndael. For more information, see the entry The Differences Between Rijndael and AES in the .NET Security blog.
Aes Class
Represents the abstract base class from which all implementations of the Advanced Encryption Standard (AES) must inherit.
- Derived
Key和IV
SymmetricAlgorithm.Key Property
Gets or sets the secret key for the symmetric algorithm.
The secret key is used both for encryption and for decryption. For a symmetric algorithm to be successful, the secret key must be known only to the sender and the receiver. The valid key sizes are specified by the particular symmetric algorithm implementation and are listed in the LegalKeySizes property.
If this property is null when it is used, the GenerateKey method is called to create a new random value.
SymmetricAlgorithm.IV Property
Gets or sets the initialization vector (IV) for the symmetric algorithm.
The IV property is automatically set to a new random value whenever you create a new instance of one of the SymmetricAlgorithm classes or when you manually call the GenerateIV method. The size of the IV property must be the same as the BlockSize property divided by 8.
The classes that derive from the SymmetricAlgorithm class use a chaining mode called cipher block chaining (CBC), which requires a key and an initialization vector to perform cryptographic transformations on data. To decrypt data that was encrypted using one of the SymmetricAlgorithm classes, you must set the Key property and IV property to the same values that were used for encryption.
For a given secret key k, a simple block cipher that does not use an initialization vector will encrypt the same input block of plain text into the same output block of cipher text. If you have duplicate blocks within your plain text stream, you will have duplicate blocks within your cipher text stream. If unauthorized users know anything about the structure of a block of your plain text, they can use that information to decipher the known cipher text block and possibly recover your key. To combat this problem, information from the previous block is mixed into the process of encrypting the next block. Thus, the output of two identical plain text blocks is different. Because this technique uses the previous block to encrypt the next block, an initialization vector is needed to encrypt the first block of data.
