A message was sent to our Math teacher.
She immediately understood that this is a simple one-to-one substitution code, with some punctuation signs.
However it took her a significant time to get the message and to restore the keyword, or rather the "keyphrase".

19050921 032116 09001705202109, 230005091605 16152523 091606082417 1216 1525 14082419 02251221 04.
0815 0816 190814140818120015 1525 14082419 100803 092419 0705 192524'15 06242507 02.


Can you accomplish both tasks and code a meaningful answer, using the same code?