In Charm 0.43, any two users can collude to achieve the ability to decrypt YCT14 data.
https://www2.hci.uni-hannover.de/papers/Tan2019.pdf
https://github.com/JHUISI/charm/issues/276
https://github.com/JHUISI/charm/blob/dev/charm/schemes/abenc/abenc_yct14.py