Relax OP_RETURN standardness restrictions

In an intriguing exchange among programmers focusing on Bitcoin development, the conversation delves into the intricacies of handling unprunable data within Bitcoin’s structure, particularly through the lens of pre-taproot raw pubkey outputs. The dialogue initially probes the concept of using proofs to validate the authenticity of certain values, which are identified as arbitrary data channels. These proofs, interestingly, are prunable, contrasting with the data they validate.

A significant portion of the discussion revolves around the challenge of proving that a piece of data is not merely data but has a specific intended function or identity, especially in a cryptographic setting. One proposed method involves employing ECDSA signatures, wherein the uniqueness and intended use of data could theoretically be verified by constraining the message of the signature to be the hash of the public key. This approach aims to circumvent the potential misuse of the signature's components for embedding arbitrary data, specifically within the (s) component of the ECDSA's (r, s) structure. However, this strategy is quickly recognized as inadequate for preventing the storage of 32 bytes of data, as one could select the 's' component as the desired data and recover the standard public key through existing algorithms, provided the public key is included in the signed message.

Further exploration into this dilemma suggests that newer consensus mechanisms or cryptographic methods, such as BIP340 or similar Schnorr signatures with key-prefixing, could offer more robust solutions regardless of the scriptPubKey style involved. These methods inherently prevent the embedding of arbitrary data via the mechanisms discussed.

Another nuanced aspect addressed is the potential for data channel exploitation through the reuse of the R-value in signatures, inadvertently "broadcasting" sensitive information. This scenario underscores a critical security concern where, in attempting to embed data across multiple outputs, one might risk exposing both the nonce and the secret key associated with the Bitcoin transaction. Such a practice not only compromises the security of the transaction but also reflects poorly on the strategy of embedding data in utxos (Unspent Transaction Outputs) for permanence within the Bitcoin ledger. The conversation highlights the complexity of managing data within Bitcoin's architecture, emphasizing the need for careful consideration of cryptographic practices and the implications of data embedding techniques.