Just putting it here in case you don't want to add clicks to the article in the OP or the blog from Martin.
The basis of the claim,
The following is the Bitcoin wallet Hal Finney used to receive the first Bitcoin transfer from Satoshi.
1Q2TWHE3GMdB6BZKafqwxXtWAWgFt5Jvm3
The following signature
HM7vpPSUbNsfDHRX6gv8xxWcVNHEc/3pOk0YrVehaGoUdbWizznfzOdELkLd1EjSXsW1oE5vHAkNAPzrAVzhuoI=
decrypts to:
-----BEGIN BITCOIN SIGNED MESSAGE-----
This Transaction was made by Paul Leroux to Hal Finney on January 12, 2009 #bitcoin
-----END BITCOIN SIGNED MESSAGE-----
Gregory Maxwell's response and exchange with Martin.
Gregory Maxwell: That signature type didn't exist until after Hal's was out of comission, so it was presumably created by someone who obtained hal's private keys after his death FWIW. You can see that address was actively sending transactions long after hal's death so *unambiguously* someone else has control of the key.
Martin Shkreli: which signature type?
Gregory Maxwell: The signature you posted isn't compatible with the Bitcoin blockchain, it's a new signature type we introduced specifically for message signing which was first released in Bitcoin 0.5.0 on November 1st 2011. But the specific format that it's in is an electrum style which wasn't even proposed until mid 2013 --
https://bitcointalk.org/index.php?topic=218471.0 I'm not sure when it was first implemented. By the time signmessage was created in late 2011 Hal was profoundly disabled and only able to use a computer with someone elses help, it wasn't widely used until years after. Other commenters have pointed out that this address was active in 2017 so that gives an obvious explanation: The message wasn't signed by Hal but whomever is using his keys now.
Martin Shkreli: this is very helpful, i am going to reach out to Finney's family to see who has these keys and why would they be signing messages... from the little I know of the Finneys, it does not seem like they would be LARPing and signing random signatures or selling the key pairs
Gregory Maxwell: Extortionists attacked his family previously, and as I understand it they sold some of Hal's bitcoin to pay for his care. It's possible that they did so by just selling the keys (or a whole wallet)-- it would be a convenient way to do so that wouldn't require figuring out how to use it. They are also periodically abused due to allegations that Hal was really Satoshi, so it's not inconceivable to me that they might try to throw people off. The scammer craig wright has proved that people will believe pretty much any claim about Satoshi, esp if it's couched in enough technical obfuscation.
Martin Shkreli: Very interesting. I have no dog in this fight, and do not care if Satoshi is Le Roux, Finney, neither, or both. It seems very likely the signature was created recently by someone who has gained access to it.
