Hello. Finding out the algorithm the shred tool relies on for its shredding operation will need more than reading the 'info coreutils shred' documentation. Unusual to be put in position to investigate here in order to get that information. Neither 'shred' 's '-v' invocation leads to communicate that.
$ echo 01 > test $ shred -v -f -n 1 -u -z test shred: test: pass 1/2 (random)... shred: test: pass 2/2 (000000)... shred: test: removing shred: test: renamed to 0000 shred: 0000: renamed to 000 shred: 000: renamed to 00 shred: 00: renamed to 0 shred: test: removed Yet this is essential information for the user in order to consider entrusting any resource whatsoever to a program for processing. P.S. Out-of scope in regard to the subject The target file to overwrite is written on Btrfs file system which design does not satisfy the program assumption - file system and hardware overwrite data in place. Btrfs being a copy-on-write that incorporates features of both log-structured and journal-operating, I therefore suppose is must be currently configured with those features on Fedora. Neither should I invoke '-u' and '--remove' since the file is written on /home, itself mounted on block device /dev/sd<_>.
