[canucker2016]

It's even worse than the key derivation. from the poster's Github repo, https://github.com/jtsylve/spice-crypt/blob/v2.0.1/SPECIFICA...:

  Modes 0–2 use a custom DES variant that retains the standard 16-round Feistel network structure but differs from FIPS 46-3 in its permutation tables, S-boxes, and key rotation direction.

Why would you need a custom DES variant? Did Cadence have a cryptographer on staff? Or did they license this DES-variant? Or was a three-letter US government agency involved?

Looks like the DES-related modes were developed back before crypto code export restrictions were relaxed.