Stob is a tool for obfuscating structured text files, e.g., tsv or csv files. Those text files are structured such that each line can be splitted into a constant number of fields using the same delimiter. The tool replaces each specified field by a random string of the same length as the original field.
$ cat test.txt
aa,1,3
bb,2,2
bb,ac,1
$ ./stob.py test.txt -d, -f 0 1
eW,r,3
bX,T,2
s7,R6,1
$ ./strdet.py -d, test.txt
0 1
$ ./stob.py test.txt -d, -f $(./strdet.py -d, test.txt)
ot,a,3
tG,0,2
mR,jW,1