Riffle shuffle a string - Cops
Python 3, 154 bytes (list of chars -> list of chars) (function) Cracked

[=o;]1-::[]:s[i,]1-::[]s:[i=R,L;2//)i(nel=s    
:)i(r fed
*tropmi modR+L+o nruter    
]:s[L,R=R,L;]s:[L=+o;))L(nel,1(tnidnar=s:R dna L elihw    
]nar morf


I doubt this will be too hard to crack, especially since riffling once is rather ineffective (you can see entire program components in the output...). This is mostly just to get things rolling. There might be some whitespace (including newlines) that I didn't copy correctly. The SHA-384 hash of my  intended solution is 
5924530418bf8cd603c25da04ea308b124fdddfc61e7060d78b35e50ead69a7fbde9200b5ee16635cc0ee9df9c954fa1.