Comment 2 for bug 1444255

With PXB 2.4.5 xtrabackup_info file also encrypted.

[root@tokubackup full]# ls -l 2017-01-20_12-33-20/
total 12356
-rw-r----- 1 root root 517 Jan 20 12:33 backup-my.cnf.xbcrypt
drwxr-x--- 2 root root 27 Jan 20 12:33 ccc
drwxr-x--- 2 root root 111 Jan 20 12:33 dbtest
drwxr-x--- 2 root root 69 Jan 20 12:33 fff
-rw-r----- 1 root root 411 Jan 20 12:33 ib_buffer_pool.xbcrypt
-rw-r----- 1 root root 12600576 Jan 20 12:33 ibdata1.xbcrypt
drwxr-x--- 2 root root 4096 Jan 20 12:33 mysql
drwxr-x--- 2 root root 8192 Jan 20 12:33 performance_schema
drwxr-x--- 2 root root 71 Jan 20 12:33 qptest
drwxr-x--- 2 root root 8192 Jan 20 12:33 sys
-rw-r----- 1 root root 205 Jan 20 12:33 xtrabackup_checkpoints.xbcrypt
-rw-r----- 1 root root 681 Jan 20 12:33 xtrabackup_info.xbcrypt
-rw-r----- 1 root root 2744 Jan 20 12:33 xtrabackup_logfile.xbcrypt

So both xtrabackup_checkpoints and xtrabackup_info files are encrypted it is making troublesome to take incremental backups.