I imagine retinal scanning is bad for long term storage (does it use blood vessel arrangements)?
Correct, and there are various pathological process which can either alter your retinal vasculature, or prevent the machine from properly scanning your retinas.I wouldn't mine my private keys being generated by dna, but that'd have to come from blood for it to be fairly accurate.
DNA can be accurately sequenced from pretty much any cell, which is why using it is a bad idea. We all shed hair and skin cells constantly. An attacker would only need to take a swab from something relatively clean that you've recently touched (like a disposable coffee cup or food wrapper) to have a fairly high chance of being able to sequence your DNA.Face and iris scanning have been spoofed with pictures before. Fingerprints can be lifted from anything you've touched.
Biometrics really aren't all that secure.
