Because that product was an embedded system running on a very small SoC. It only had 1MB of flash and 192k of SRAM. It's theoretically possible to run CL on a system that small -- Coral Common Lisp ran on a Mac Plus with 1MB of RAM back in the 1980s -- but nothing off-the-shelf will do that today.

(I did, however, put a little Scheme interpreter on it as an easter egg :-)

I do have some CL code that supports the crypto project. The back-end for this:

https://stage.sc4.us/sc4/sc4tk.html

is written in CL (though all the actual encryption is done client-side in Javascript). I also have some prototype crypto code that I don't really use for anything, including this double-ratchet implementation:

https://github.com/rongarret/tweetnacl/blob/master/ratchet.l...

and some elliptic curve code:

http://www.flownet.com/ron/lisp/djbec.lisp