The `WriteSecretIntoBuffer` method populates the supplied buffer with the raw secret value. The reason this API takes the buffer as a parameter rather than returning a `byte[]` directly is that this gives the caller the opportunity to pin the buffer object, limiting secret exposure to the managed garbage collector.
The `Secret` type is a concrete implementation of `ISecret` where the secret value is stored in in-process memory. On Windows platforms, the secret value is encrypted via [CryptProtectMemory](https://msdn.microsoft.com/library/windows/desktop/aa380262(v=vs.85).aspx).