What cipher block mode is used with SPECK? Block based disk encryption is complicated to get right due to replay attacks of blocks over time and IV issues. There are established best-practice compromises with AES, but I dont know if they apply to other block ciphers and doubt they are tested.
XEX, unfortunately. That's a mistake. Unauthenticated tweakable wide-block cipher modes are designed for simulated hardware disk encryption. That's not what an encrypted filesystem is: a filesystem knows where files begin and end, and has space for metadata. Filesystem encryption should use authenticated encryption.
