Computing on Bitcoin #69
December 12, 2025 - Week 50
Welcome to this week’s edition of Computing on Bitcoin News, your window into the future of programmable Bitcoin.
We continue to see incredible momentum across the ecosystem as researchers, engineers, and builders push the boundaries of what’s possible.
Let's dive in.
A new post by GOAT Network announces BitVM2-GC with DV-Snark, a milestone aimed at shrinking on-chain fraud-proof data by several orders of magnitude. By combining garbled circuits with a DV-Snark variant, the update advances BitVM2’s path toward Bitcoin-native security while keeping verification costs practical for real-world L2 operation.
goat.network/blog
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GOAT Network Introduces BitVM2-GC with DV-Snark
By utilizing the zkVM(Ziren) to implement a verifiable garbled circuit scheme of DV-SNARK verifier, our BitVM2-GC cuts on-chain fraud-proof data by ~1000×, and achieve smallest off-chain storage among all known BitVM2 designs, and the GC proving time is less than 1 hour with a very low cost (less than $3.88).
A new research paper, “Cardinal: Bridging Bitcoin with Ownership Preservation,” introduces a trust-minimized Bitcoin bridge that guarantees users always withdraw the exact coins they deposited, a property multisig and prior BitVM-based bridges don’t provide. Cardinal extends the BitVM model through a generalized execution layer called ChainVM, and the paper shows how this framework can be instantiated using BitVMX.
eprint.iacr.org
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Cardinal: Bridging Bitcoin with Ownership Preservation
Cross-chain bridges have emerged as key components of blockchain infrastructure, enabling digital assets to flow across chains and benefit from non-native features. While early bridge designs were fraught with brittle trust assumptions, more recent designs, even within Bitcoin's script limits, can operate in a trust-minimized setting.
Annabelle Huang explains how Altius Labs is building a plug-and-play high-performance execution layer for any L1 or L2, arguing that crypto’s next wave needs faster infrastructure—and that once BitVM matures, similar upgrades could eventually apply to Bitcoin as well.
selballmer.medium.com/
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Annabelle Huang on Building High-Performance Infrastructure for Web3
“Our role is not to build another fast L1 or L2, but to build the infrastructure solution to empower crypto-native teams, institutions, and enterprises to build their own high-performance chain.”
BitMEX Research published a detailed examination of the long-known “64-byte transaction” quirk in Bitcoin, showing how such transactions can be confused with Merkle tree internals and potentially exploited to deceive SPV clients.
bitmex.com/blog
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64 Byte Transactions
In this piece we are focusing on the issues of the “64 byte transactions.” The trick involved here is that the data in the inner nodes in the Merkle trees that make up Bitcoin blocks are 64 bytes. The hash of a Bitcoin transaction, the TXID, is 32 bytes.The inner branches of the second lowest row of the Merkle tree hashes two Bitcoin TXIDs concatenated together. This makes 64 bytes.
The security vulnerability is that this 64 bytes of data could be confused with a 64 byte Bitcoin transaction. For instance, an attacker could create a 64 byte Bitcoin transaction, to confuse or trick a would be victim into accepting an incoming payment.
Thanks for reading this week's edition of Computing on Bitcoin News!
The world of Bitcoin computing continues to accelerate, fueled by collaboration, experimentation, and a shared goal of pushing the boundaries of what’s possible.
Stay tuned for more updates.
The Fairgate Team