Once the ID ends in ‘t1’, this means that your files are encrypted with an offline key. This gives a chance that you can decrypt .bboo files for free. To date, the following STOP Djvu variants can be decrypted: gero, .hese, .seto, .peta, .moka, .meds, .kvag, .domn, .karl, .nesa, .noos, .kuub, .reco, .bora, .nols, .werd, .coot, .derp, .meka, .mosk, .peet, .mbed, .kodg, .zobm, .msop, .hets, .mkos, .nbes, .reha, .topi, .repp, .alka. As you can see, there are no ‘bboo’ on this list yet. This means you have to wait. I recommend that you try to decrypt .bboo files from time to time, since only security researchers will find the offline key, then decryption of these files will be possible.
how to decrypt bboo file