Adam Back, the longtime Bitcoin cryptographer whose early work was referenced by Satoshi Nakamoto and who has repeatedly denied speculation that he is Bitcoin’s creator, recently sharpened his critique of Ethereum’s foundational design.
In response to warnings from Ethereum researchers that artificial intelligence could potentially undermine the cryptographic signatures protecting both Bitcoin and Ethereum wallets far sooner than quantum computing threats—possibly in months rather than years—Back highlighted Bitcoin’s Unspent Transaction Output (UTXO) model.
He suggested that Satoshi’s choice reflected a sophisticated grasp of distributed systems and peer-to-peer programming, noting that the UTXO approach treats discrete outputs much like physical cash that is spent and recreated.
In contrast, he described early Ethereum developers as inexperienced and said they rebuilt around what he viewed as a flawed account-based architecture despite prior cautions.
Ethereum’s account model tracks persistent balances and contract state more like a traditional ledger, and researchers have explored optional UTXO-style features in proposals such as EIP-8141, but Back’s comments framed Bitcoin’s design as better suited to avoid certain concurrency and state issues in decentralized networks.
These remarks arrive amid mounting operational and legal pressures on ventures associated with Back, as detailed in a late-September report.
Blockstream, the infrastructure firm he co-founded and where he serves as CEO, was hit by what has been described as 2026’s largest crypto theft. On September 6, attackers exploited a caching flaw in Elements, the software underlying the Liquid Network—a federated Bitcoin sidechain developed by Blockstream for faster, more private transfers of bitcoin.
By minting roughly 4,000 unbacked L-BTC tokens and then redeeming them through an authorized peg-out, the attackers extracted about $319 million in real bitcoin from the federation’s reserves.
They identified themselves via on-chain messages as white-hat researchers, negotiated after a software patch was deployed, and returned approximately 85 percent of the funds, or roughly 3,400 BTC worth about $272 million.
Roughly $47 million remained outstanding, which the attackers treated as a bounty; Blockstream rejected demands for further payment, characterizing the retention as unauthorized withholding rather than responsible disclosure.
The network was temporarily paused, peg operations disrupted, and L-BTC trading suspended at exchanges while recovery continued, leaving a temporary shortfall in backing.
Separately, a high-profile effort to list a Bitcoin treasury vehicle collapsed.
BSTR Holdings, a project promoted by Back that aimed to bring a substantial bitcoin position—originally structured around more than 30,000 BTC plus additional financing—public through a merger with a Cantor Fitzgerald-sponsored SPAC, saw the deal terminated in August 2026.
The unwind triggered a $15 million termination obligation, with staged payments due in September and December.
Market conditions and renegotiation attempts contributed to the failure of the original terms.
A Bitcoin mining operation that Back helped establish and in which he held a minority interest after its spin-off from Blockstream has also faced multiple civil disputes.
Partner entity Exacore, which operates multiple mining sites, has been named in lawsuits alleging unpaid electricity, equipment, and related obligations totaling in the low millions, following significant capital raised through notes and other instruments tied to expected production.
Blockstream has stated it maintains no operational affiliation with Exacore. These developments coincide with the industry’s broader post-boom adjustments, underscoring liquidity, counterparty, and technical risks even for long-established Bitcoin infrastructure players.