Emsisoft Decrypter for KeyBTC can decrypt files if you find a ransom note called DECRYPT_YOUR_FILES.txt on your system that asks you to contact email@example.com for decryption.
KeyBTC is spotted if you have the ransom note DECRYPT_YOUR_FILES.txt on your desktop with the firstname.lastname@example.org email address in it.
There is no way for the decrypter to figure out whether you were actually hit by the malware or not. So only try it if you are 100% sure it matches your infection. The decrypter will create backups of all encrypted files it attempted to decrypt. So you will need enough free storage for all the backup copies. If you don't have enough storage capacity, you can disable the backup creation under options.
The decrypter also performs some basic checks whether the resulting file somehow makes sense and resembles a known file format. This works fine but in the off-chance that you have some file formats encrypted that the decrypter can't recognize, you may have to disable those safety checks in the options as well.