asp.net core blazor webassembly subtlecrypto - how to use a custom secret key

Question

We are trying to integrate Subtlecrypto into our blazor webassembly app. It seems this is the only cryptography package that blazor wasm supports.

According to the official example, there is not a way to change/custom the secret key. If the secret is assigned at startup, the key is fixed and used across the application:

using Blazor.SubtleCrypto;

builder.Services.AddSubtleCrypto(opt => 
    opt.Key = "ELE9xOyAyJHCsIPLMbbZHQ7pVy7WUlvZ60y5WkKDGMSw5xh5IM54kUPlycKmHF9VGtYUilglL8iePLwr" 
    );

Or one can use random key and iv that the application has no control.

In our app we hope to ask the user to enter a key, which is used to encrypt some data. A fixed key can work but it seems less secure.

Is there a way to achieve a custom secret key?

score 1 · Accepted Answer · answered Jan 21 '23 at 15:42

Below is what I did:

    var options = new CryptoOptions() { Key = "some_secret"};
    var crypto = new CryptoService(jsRuntime, options);
    string s = "abc";
    CryptoResult encrypted = await crypto.EncryptAsync(s);

    Console.WriteLine("Encrypted: " + encrypted.Value);

    string d = await crypto.DecryptAsync(encrypted.Value);

    Console.WriteLine("Decrypted: " + d);

asp.net core blazor webassembly subtlecrypto - how to use a custom secret key

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