CASELAW-EPO - reviews of EPO Boards of Appeal decisions

EP 3 095 044 B1 relates to block mining methods and apparatus.  

What the invention is about

The invention builds upon the conventional Bitcoin mining process which successively hashes the first and second block of the candidate header.

The hasher has an expander that takes and processes a block of the input message and produces a message schedule, and a compressor that takes and processes the message schedule and produces a hash value. Successive blocks of the header are expanded and fed into the compressor which keeps updating the hash value in a set of registers.

In Bitcoin, only the second block of the header, containing the nonce is actually changing each time the header is hashed. As the first block is not changing its compressed value can be reused as the starting value for the hash value in the compressor for each new value of the second block.

This value is called the mid-state.

Claim 1 as granted reads:

“A method for mining a block in a blockchain, preferably Bitcoin, …… comprising the steps of:

[1] Computing a plurality, m, of mid-states, each as a function of selectively varying a selected first portion of the block header, starting from a respective unique mid-state of said plurality mid-states by a mid-state generator entity, wherein said mid-state generator entity computes a new-mid-state every compressor entity pipe clock with each mid-state being passed down the compressor entity chain at that same pipe clock rate;

[1.1] Distributing said computed plurality of m mid-states to a beginning stage of said plurality of compressor entities,

[2] Computing by said single expander entity a message schedule, said message schedule comprising ……

Brief outline of the procedure

Claim 1 as granted infringed Art 123(2). The same applied to claim 1 of AR1-5. AR6-7 infringed Art 123(3). AR8-9 filed during OP before the OD were not admitted.

The patent was thus revoked and the proprietor appealed.

The board confirmed the revocation.

We will deal only with AR6, as the problem is also present in other requests.

The Board’s decision

The board agreed with the OD that claim 1 of AR6 shifts the protection conferred by the granted patent, contrary to the requirements of Art 123(3).

The amendments to claim 1 of AR6 would mean that the claim would now encompass an arrangement with multiple expanders, an arrangement which was previously not covered by the scope of protection conferred by the granted claim.

Furthermore, the shift of the mid-state definition from what is “computed” to what is “distributed”, meaning that the amended claim now covers a much larger scope with regard to how the plurality of mid-states should be computed.

The amendment causing this shift is the deletion of the wording “starting from a respective unique mid-state of said plurality mid-states by a mid-state generator entity” from feature [1] in claim 1 of all those requests. This amendment generalises feature [1], which is no longer limited to starting from a respective unique mid-state.

In AR6, this wording was essentially transposed from feature [1] to feature [1.1].

Contrary to the proprietor’s view, the board judged that the mere fact that the wording remained in the claim is necessary but not sufficient to meet the requirements of Arti 123(3).

The board agreed with the OD that this Article prohibits any shift in a claim’s scope, including shifts resulting from partial generalisations of particular claim features.

A shift in scope arising from such a partial generalisation cannot be remedied by narrowing other aspects of the claim.

Comments

This decision is interesting as it makes clear simply moving a specific feature within a claim to another part of the claim can nevertheless extend the scope of protection, if one feature of the claim is thereby generalised, whilst another is more limited.

T 0450/23