Eu faria assim:
$ sudo dmsetup ls
crypthome (254:0)
$ sudo dmsetup -v table /dev/mapper/crypthome
Name: crypthome
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 1
Event number: 0
Major, minor: 254, 0
Number of targets: 1
UUID: CRYPT-LUKS1-87863643a6aa43c191f69ee3a2b3301a-crypthome
0 870313984 crypt aes-xts-plain64 0000000000000000000000000000000000000000000000000000000000000000 0 8:2 4096