verdandi# dd if=/dev/zero of=myVnHDD.iso count=102400
102400+0 records in
102400+0 records out
52428800 bytes transferred in 2.822051 secs (18578261 bytes/sec)

verdandi# mdconfig -a -t vnode -u 4 -f myVnHDD.iso

verdandi# ll /dev/md4 
crw-r-----  1 root  operator    4,  23 Feb  9 09:12 /dev/md4

verdandi# newfs /dev/md4
/dev/md4: 50.0MB (102400 sectors) block size 16384, fragment size 2048
        using 4 cylinder groups of 12.52MB, 801 blks, 1664 inodes.
super-block backups (for fsck -b #) at:
 160, 25792, 51424, 77056

verdandi# mount /dev/md4 /mnt

verdandi# mount
...
/dev/md4 on /mnt (ufs, local)

verdandi# cd /mnt

verdandi# echo 'very secret stuff' > secret.txt

verdandi# ls -al
total 8
drwxr-xr-x   3 root  wheel     512 Feb  9 10:12 .
drwxr-xr-x  22 root  wheel     512 Feb  8 19:06 ..
drwxrwxr-x   2 root  operator  512 Feb  9 09:58 .snap
-rw-r--r--   1 root  wheel      18 Feb  9 10:12 secret.txt

verdandi# umount -f /mnt

verdandi# mdconfig -d -u 4

verdandi# dd if=myVnHDD.iso | openssl enc -des3 -salt | dd bs=10240 of=myVnHDD.iso.enc
enter des-ede3-cbc encryption password:
Verifying - enter des-ede3-cbc encryption password:
102400+0 records in
102400+0 records out
52428800 bytes transferred in 12.352662 secs (4244332 bytes/sec)
89+12570 records in
89+12570 records out
52428824 bytes transferred in 12.304915 secs (4260803 bytes/sec)

verdandi# strings myVnHDD.iso.enc | grep -i secret

verdandi# strings myVnHDD.iso | grep -i secret
very secret stuff
secret.txt

verdandi# rm -rf myVnHDD.iso

verdandi# dd bs=10240 if=myVnHDD.iso.enc | openssl enc -d -des3 -salt | dd of=myVnHDD.iso
enter des-ede3-cbc decryption password:
5120+1 records in
5120+1 records out
52428824 bytes transferred in 11.465478 secs (4572755 bytes/sec)
102400+0 records in
102400+0 records out
52428800 bytes transferred in 11.451799 secs (4578215 bytes/sec)

verdandi# mdconfig -a -t vnode -u 4 -f myVnHDD.iso

verdandi# mount /dev/md4 /mnt

verdandi# cat /mnt/secret.txt 
very secret stuff
verdandi#