I am trying to implement a deterministic encryption scheme in .NET. This link suggests I use AES-SIV mode encryption. An alternative is to use AES-CTR [ k1, nonce, message] mode with HMAC[ k2, message] as the nonce. This is effectively the same as AES-SIV.
In .NET, there is no implementation of AES-SIV. AES-CTR mode is also not available in .NET. The only .NET compatible library which implements AES-SIV I can find is Miscreant .NET. This is not FIPS validated.
Does anyone have any suggestions on how to implement a deterministic encryption scheme in .NET?
This post is a continuation of a previous post.
My Project: I have several bankers who will send the balance information for thousands of bank accounts to a server. The account numbers will be encrypted using this scheme prior to sending to the server for security purposes. The server deliberately will not have the private key [I'm setting up a zero-knowledge encryption scheme]. On the client side, Banker1 and Banker2 must be able to encrypt the account number in a deterministic way that allows any Banker to decrypt account numbers returned from the server. For this reason, I decided to use HMAC(message) as the nonce for my encryption scheme and append it to the ciphertext. AES-CTR[ k1, nonce, message] || HMAC[ k2, message] where nonce = HMAC[ k2, message].