if this's using ephemeral keys with no forward secrecy and no ledger of interactions, what part of it’s actually bitcoin style besides the name?
Having no actual use?
Bitcoin is great for prospecting, laundering money across borders, and scamming gullible people. It's also easier to hide a stash of stolen bitcoins from the authorities for after you get released from jail than it is to hide a stash of actual money. Bitcoin is certainly no alternative to actual money but it's not entirely useless.
I think these Twitter DMs only does the scamming the gullible part, as you need to pay to use the feature and this is scamming people into thinking they're paying for secure messaging.
prospecting? like, finding diamonds or oil or copper or something?
is the bitcoin a fundraising mechanism for juniors or something?
can you explain tbe mechanism?
Key derivation from a PIN? Although that's an implementation detail of the key backup rather than anything inherent in the actual messaging so who knows.
He didn't say it was Bitcoin style, just that it used "(Bitcoin style) encryption".
I was going to point out that Bitcoin does not use encryption; but technically I think it's signature algorithm (ecdsa) can be thought of as a hashing step, followed by a public-key based encryption step.
So, in the most charitable reading, it using ecliptic curve asymmetric encryption. Presumably for the purpose of exchanging a symmetric key, as asymmetric encryption is very slow. In other words, what basically everything written this decade does. Older stuff would use non EC algorithms, that are still totally fine, but need larger keys and would be vulnerable to quantum computers is those ever become big enough.
> but technically I think it's signature algorithm (ecdsa) can be thought of as a hashing step, followed by a public-key based encryption step.
It really can't. If you're extremely drunk you can think of it as similar to hashing followed by a public-key based decryption step (signing uses the private key, as does decryption) but that's about as good an analogy as calling a tractor-trailer a container ship because both haul cargo. The actual elliptic-curve part of the operation isn't encryption or decryption, and thinking of it as such will lead to error.
RSA does have a simpler correspondence in that the fundamental modular multiplication operation is shared between decryption and signing (or between encryption and verification). But modular multiplication alone isn't secure, it's the "padding" that turns modular multiplication with a particularly-chosen modulus from some basic math into a secure encryption/signature system. And the padding differs, and the correspondence doesn't hold in real systems. RSA without padding is just sparkling multiplication.
I was going to point out that Bitcoin does not use encryption
Yeah Musk as not very technical person would hardly know the difference.
Bitcoin does use encryption for messaging, but I don't know if this is what Musk was referencing: https://bitcoinops.org/en/topics/v2-p2p-transport/