/// <summary>
/// Initializes a new instance of the <see cref="HmacSha512"/> using the given key.
/// </summary>
/// <exception cref="ArgumentNullException"/>
/// <param name="key">Key to use, if the key is bigger than 64 bytes it will be hashed using <see cref="Sha512"/></param>
public HmacSha512(byte[] key)
{
hashFunc = new Sha512();
Key = key;
}
/// <summary>
/// Initializes a new instance of the <see cref="HmacSha512"/>.
/// <para/> Useful for using the same instance for computing HMAC each time with a different key
/// by calling <see cref="ComputeHash(byte[], byte[])"/>
/// </summary>
public HmacSha512()
{
hashFunc = new Sha512();
}