Also the keys can be any random secret...

Meaning you could use PBKDF2 of your favorite passphrase as your private key, then keep it in organic memory.

Personally, I would love to see a strategy for generating a private from an analog picture.. But I don't see a good way to do it reliably.. Maybe one could generate it from error correction bits in a QR code.

I'm not sure you can use a KDF because it requires a salt.

I'm working on a blog post on deterministic passwords (i.e. not keys for ECC), but I guess that if you really want determinism you can do something similar, maybe sha3.512 and "cut" a 256-bit ECC key.

This is the post, still a draft. Hopefully I'll publish it next week, but if you have any comments, they are more than welcome! https://medium.com/@0x0ece/how-i-manage-my-passwords-technic...

> Personally, I would love to see a strategy for generating a private from an analog picture.. But I don't see a good way to do it reliably.. Maybe one could generate it from error correction bits in a QR code

Not clear exactly what you meant, but but deriving a key from a photograph shouldn't be that difficult. A good perceptual hash should work, maybe some preprocessing is needed (straighten/crop/normalize/resize). It helps that the amount of data in an image is absolutely massive compared to typical key size.

For RSA keys shouldn't it be possible to store some 256 bit seed and then use a deterministic algorithm to convert that to a 4096 bit key?

Prime number generation is typically done like this. Pick a random number, then add 2 until you get a prime.

So you can do something similar. Pick a deterministically generated bit string, and use as key the next prime number (you need to do it twice, for p and q).

You certainly get less security and I unfortunately don't have any reference to quantify that.

As I was saying in another post, I'm writing about deterministic password generation (i.e. not RSA keys). Draft here: https://medium.com/@0x0ece/how-i-manage-my-passwords-technic...

Even if there is, such a key would be much less safe (assuming the attacker knew the algorithm, which must be assumed, otherwise why keep the key in a safe?)