Thanks for your suggestions: Can confirm start/end bytes are wrong. Tried to open in Shotwell, GIMP, Firefox, Google Chrome w/o results.
I assume the hard drive is ok: I also have some git repositories on the drive and the checksums for git are correct. Every other file on the drive is ok, so cryptolocker malware could have only been on my phone at that time.
No worries and thanks a lot for your suggestions/answers!