let HMACStream (key: byte[]) (outputStream: Stream) : Stream * HMACSHA256 =
if key.Length <> 32 then raise KeySizeError
let hmac = new HMACSHA256 (key)
new CryptoStream (outputStream, hmac, CryptoStreamMode.Write) :> Stream, hmac
let HMACStream (key: byte[]) (outputStream: Stream) : Stream * HMACSHA256 =
if key.Length <> 32 then raise KeySizeError
let hmac = new HMACSHA256 (key)
new CryptoStream (outputStream, hmac, CryptoStreamMode.Write) :> Stream, hmac