在C＃中使用sha1算法使用用户的秘密密钥进行哈希

Question

I need to hash a string according to the sha1 algorithm, with the user's secret key, something like: hash = hash (string, secret_key).

I use this code:

byte[] data = sha1.ComputeHash(Encoding.UTF8.GetBytes(input));

But I can not find how to use the secret key in this algorithm.

Answer 1

The hash is the result of applying a hash function to data. It maps arbitrary data to fixed size value. This does not require any kind of secret.

The cryptographic process which uses hashes and secret keys is signing data. You may want to create a hash of your data and a MAC (message authentication code) based on public/private key cryptography using the private key.

A hash tells you only that data was modified or not.

A MAC uses any kind of secret, thus it protects also against manipulation. Generally, MACs only work when the sender and receiver know each other.

You could do something like:

public string SignData(string message, string secret)
{
    var encoding = new System.Text.UTF8Encoding();
    var keyBytes = encoding.GetBytes(secret);
    var messageBytes = encoding.GetBytes(message);
    using (var hmacsha1 = new HMACSHA1(keyBytes))
    {
        var hashMessage = hmacsha1.ComputeHash(messageBytes);
        return Convert.ToBase64String(hashMessage);
    }
}