Dominik, can we use AesCryptoServiceProvider instead of RijndaelManaged for key transformations when native is not available ? AesCryptoServiceProvider is at least 3 time faster than RijndaelManaged on my machine. Keepass uses a fixed key size of 256 bits and ECB mode for transform, both are supported by AesCryptoServiceProvider. I created a test to verify, using code from TransformKeyManaged (AesKdf.cs): https://gist.github.com/Anadorr/fa1911250ebeacdeb1f8646571aaa1b7