A few months ago there was a formal proposal for sighash_noinput, it’s a new OPCode to be used in a technology called Eltoo. Eltoo is built on top of Lightning to resolve problems with malicious channel closing, currently the way to solve this is by giving all of the channel’s funds to the victim, but this, in some cases, would require the entire channel’s history to be broadcast, which isn’t remotely efficient.

Sighash_noinput brings a solution to this case, as mentioned in the Bitcoin BIP:

It removes any commitment to the output being spent from the signature verification mechanism. This enables dynamic binding of transactions to outputs, predicated solely on the compatibility of output scripts to input scripts.

But there was some controversy that this enables other malicious use cases if it was used in anything other than LN and Segwit transactions, developer Christian Decker mentioned that this is to be used only in very specific scripts and should not be available for general wallets to sign with.

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