indeed, i once added a proof-of work requirement to public keys on an open relay server protocol, in additon to posk, in order to make it harder to roll new keys and access the network as a spammer/scammer.   not hard to embed anything in a public key, but you can't embed too much, especially if you want mobile devices to be able to generate a new key in under a few minutes. 

On Mon, Aug 21, 2023 at 6:46 PM symphonicbtc via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:
It is important to also note that proof of secret key schemes are highly data inefficient and likely would have a higher cost for users than simply allowing arbitrary data to continue. In ECDSA, purposely re-using k values allows you to encode data in both k and the entire secret key, as both become computable. Or, one could bruteforce a k value to encode data in a sig, as is done in some compromised hardware key exfiltration attacks. Additionally, one can bruteforce keys in order to encode data in the public key.

It is very difficult and expensive to attempt to limit the storage of arbitrary data in a system where the security comes from secret keys being arbitrary data.

Symphonic

------- Original Message -------
On Monday, August 21st, 2023 at 4:28 PM, John Tromp via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:


> > If we ban "arbitrary data", however you want to define it, then actors will
> > simply respond by encoding their data within sets of public keys. Public
> > key data is indistinguishable from random data, and, unless we are willing
> > to pad the blockchain with proof of knowledge of secret keys, there will be
> > no way to tell a priori whether a given public key is really a public key
> > or whether it is encoding an inscription or some other data.
>
>
> Note that in the Mimblewimble protocol, range proofs already prove
> knowledge of blinding factor in Pedersen commitments, and thus no
> additional padding is needed there to prevent the encoding of spam
> into cryptographic material. This makes pure MW blockchains the most
> inscription/spam resistant [1].
>
> [1] https://bitcointalk.org/index.php?topic=5437464.msg61980991#msg61980991
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