Hi Eric, It is. This is what is implemented in Bitcoin Core, see [this snippet](https://github.com/bitcoin/bitcoin/blob/41544b8f96dbc9c6b8998acd6522200d67cdc16d/src/validation.cpp#L4547-L4552) and section 4.1 of the document you reference: > Another check that was also being done in CheckBlock() relates to the coinbase transaction: if the first transaction in a block fails the required structure of a coinbase – one input, with previous output hash of all zeros and index of all ones – then the block will fail validation. The side effect of this test being in CheckBlock() was that even though the block malleability discussed in section 3.1 was unknown, we were effectively protected against it – as described above, it would take at least 224 bits of work to produce a malleated block that passed the coinbase check. Best, Antoine On Tuesday, June 18th, 2024 at 12:15 AM, Eric Voskuil wrote: > Hi Antoine, > > Regarding potential malleability pertaining to blocks with only 64 byte transactions, why is not a deserialization phase check for the coinbase input as a null point not sufficient mitigation (computational infeasibility) for any implementation that desires to perform permanent invalidity marking? > > Best, > Eric > > ref: [Weaknesses in Bitcoin’s Merkle Root Construction](https://lists.linuxfoundation.org/pipermail/bitcoin-dev/attachments/20190225/a27d8837/attachment-0001.pdf) > > -- > You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group. > To unsubscribe from this group and stop receiving emails from it, send an email to bitcoindev+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/bitcoindev/72e83c31-408f-4c13-bff5-bf0789302e23n%40googlegroups.com. -- You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group. To unsubscribe from this group and stop receiving emails from it, send an email to bitcoindev+unsubscribe@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/bitcoindev/heKH68GFJr4Zuf6lBozPJrb-StyBJPMNvmZL0xvKFBnBGVA3fVSgTLdWc-_8igYWX8z3zCGvzflH-CsRv0QCJQcfwizNyYXlBJa_Kteb2zg%3D%40protonmail.com.