问题
I'm looking at an C# AES asymmetric encryption and decryption example here and not sure if i should store the IV in a safe place (also encrypted??). Or i can just attach it to the encrypted text for using later when i with to decrypt. From a short reading about AES it seems it's not needed at all for decryption but i'm not sure i got it right and also the aes.CreateDecryptor(keyBytes, iv) need it as parameter.
I use a single key for all encryptions.
回答1:
It's fairly standard to transmit the encrypted data as IV.Concat(cipherText). It's also fairly standard to put the IV off to the side, like in PKCS#5.
The IV-on-the-side approach matches more closely with how .NET wants to process the data, since it's somewhat annoying to slice off the IV to pass it separately to the IV parameter (or property), and then to have a more complicated slicing operation with the ciphertext (or recovered plaintext).
But the IV is usually transmitted in the clear either way.
So, glue it together, or make it a separate column... whatever fits your program and structure better.
回答2:
Answer: IV is necessary for decryption as long as the content has been encrypted with it. You don't need to encrypt or hide the IV. It may be public.
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The purpose of the IV is to be combined to the key that you are using, so it's like you are encrypting every "block of data" with a different "final key" and then it guarantees that the cipher data (the encrypted one) will always be different along the encryption (and decryption) process.
This is a very good illustration of what happens IF YOU DON'T use IV.
Basically, the encryption process is done by encrypting the input data in blocks. So during the encryption of this example, all the parts of the image that have the same color (let's say the white background) will output the same "cipher data" if you use always the same key, then a pattern can still be found and then you didn't hide the image as desired.
So combining a different extra data (the IV) to the key for each block is like you are using a different "final key" for each block, then you solve your problem.
来源：https://stackoverflow.com/questions/44694994/storing-iv-when-using-aes-asymmetric-encryption-and-decryption