CODEWITHSUNDEEP
cryptographyaesauto-generate
Richard
Richard

Reputation: 19

C# CryptoGraphy AES key generate?

I have a question about when AES generate a key and IV how would the user know what the key is or how the program would know which key to use like it is generated. For example like if there is a encryption method that encrypt the file and generate the key and IV. When the program restarts or be used another day they would want to use the decryption but how would you know or the program knows thats the key for that file.

I understand the decryption and encryption by looking at it. I just dont know where the information is store to retrieve the key?

Upvotes: 1

Views: 961

Answers (1)

Maarten Bodewes
Maarten Bodewes

Reputation: 93968

Key management is a large part of any cryptography related protocol. It takes a book or so to explain.

One of the most known methods is using a password (see password based encryption in PKCS#5, where a key is generated from a (stored) salt, number of iterations and of course the password (encoded to bytes). Another option is to store the key on some removable device like an USB key.

Usually the main key is not used to encrypt the data, but an intermediate key called the data or session key is used. For instance PGP encryption generates a data key and encrypts it with a public key of an asymmetric key pair.

Then there are smart cards, TPM modules, HSM's, key containers (possibly provided by the OS), key sharing protocols etc. etc. etc..

So ... it depends.

Sometimes it is easier to think of a key as another secret. By encrypting something you've only "compressed" your larger secret (your plaintext) into a smaller secret (the key) that you have to keep and manage. This secret however may have been generated in advance, or may have been generated by other means. If you just generate your key at the same time and location as your ciphertext, you haven't solved anything yet, you only made your secret smaller.

It's easier for the IV, the IV can simply be stored with (commonly, in front of) the ciphertext.

Upvotes: 1

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