The blockchain trilemma was long considered a largely unsolvable problem for blockchain. Three desirable features for blockchains — scalability, decentralization, and security — and protocols could only achieve (at most) two of the three.
In December 2025, Ethereum rolled out its solution to the problem with its Fusaka upgrade. With these edits, Vitalik Buterin claims that the blockchain trilemma is essentially solved. However, it will be years before they’re able to take full advantage of the benefits that the update provides.
The Blockchain Trilemma Explained: Scalability, Decentralization, Security
The term blockchain trilemma was coined to describe three critical features for blockchains that were largely impossible to fully achieve.
The three elements of the trilemma include:
Scalability: Blockchains like Ethereum are designed to support a wide variety of dApps, as well as various cryptocurrencies and other tokens. The ability to process large volumes of transactions quickly is essential to compete with “competitors” like the Visa network.
Decentralization: Blockchain was initially created to provide an alternative to the traditional financial system (TradFi). A key element of this was eliminating the centralized power and authority that enabled the financial crisis that sparked blockchain’s creation.
Security: Blockchain platforms are designed to implement a financial system and distributed computer whose security is enforced by cryptography and algorithms rather than the reputation and assurances of a centralized authority, like a bank. For this reason, the security of every element of the system is of paramount importance.
Historically, it was seen as impossible to achieve more than two of the three elements of the blockchain trilemma. As a result, various platforms and solutions focused on optimizing two of the three at the cost of the third.
For example, Ethereum was designed to be highly decentralized and secure, making it a very trustworthy system to build dApps on and hold Ether. However, its transaction rate was very limited as a result since it required many nodes in the network (decentralization) to review each transaction before accepting a block containing it (security). Since nodes may have limited computational power or storage to devote to this task, throughput was limited to avoid driving some validators out of the market.
Other platforms took different approaches to managing the blockchain trilemma. For example, some smart contract platforms have more centralized authority, where a small group has the ability to vote on and execute actions that affect the blockchain as a whole. By limiting their decentralization, these platforms have the potential to achieve greater throughput than Ethereum without compromising security.
What the Fusaka Upgrade Changed on Ethereum
Ethereum’s ability to “solve” the blockchain trilemma stems from significant technological evolution from the time when the term was coined. The new updates have introduced the PeerDAS protocol and built on the availability of ZK-EVMs to reduce data storage and networking requirements and the computational complexity of transaction validation in ways that weren’t possible in the past.
PeerDAS
Data availability (DA) is one of the most significant factors throttling Ethereum Layer 2s. Rollups based on Ethereum send data in blobs to Layer 1 for verification. The amount of data that can be sent limits the transaction throughput of these rollups.
Recent updates to Ethereum have introduced the concepts of blobs and expanded their capacity. However, it was necessary to maintain a balance between Layer 2s’ need for larger blobs and Layer 1 nodes’ limited capacity for blob storage.
The Fusaka update introduced Peer-to-Peer Data Availability Sampling (PeerDAS), which allows blockchain nodes to store a portion of the data contained within a blob while still being able to verify the entirety of the data. This is implemented via sharding, where different nodes store different pieces and can access them through peer-to-peer communications. Nodes perform sampling of the data, accessing approximately 1/8 of the total data while being relatively certain of the availability of all data within the blob.
With Fusaka and earlier updates, blob capacity was increased substantially without putting an equivalent burden on node operators. Long term, Buterin says that PeerDAS may be applied to Layer-1 Ethereum as well, dramatically expanding its ability to process transactions.
ZK-EVMs
Another key limitation on Ethereum’s throughput and scalability is transaction validation. In a decentralized network, various nodes can’t depend on other nodes to verify that each transaction in a block is correct and valid.
As a result, nodes were required to independently validate and execute each transaction to verify the correctness of the state updates associated with a block. However, this required significant computational resources and access to the entirety of the transaction data contained within the block.
The growth of Zero-Knowledge Ethereum Virtual Machines (ZK-EVMs) offers an alternative, where nodes can simply verify the correctness of a transaction without executing it themselves. Instead, they verify the correctness of a zero-knowledge proof (ZKP), which proves the accuracy of a state update, such as those provided by a Layer 2.
Zero-knowledge proofs are more compact and require fewer resources to validate than are required to fully execute all of the transactions that they cover. As a result, this further enhances Ethereum’s scalability by reducing both data storage and computation requirements.
Security Implications of the Ethereum Updates
Ethereum’s updates are designed to enhance the scalability of the protocol while maintaining decentralization and security. It accomplishes this by introducing new solutions and technologies that move away from explicit, personal validation of information to reliance on strong guarantees of data availability and zero-knowledge proof validation.
With this transition, the security of the blockchain boils down to the security of the PeerDAS and ZKP code in question. With nodes sampling only 1/8th of blob data, weaknesses in the sampling process might allow an attacker to make it seem that all data is available when a significant portion is missing. Similarly, ZKPs rely on certain assumptions and cryptographic algorithms that could undermine their security if they prove to be incorrect or insecure.
At the moment, the updates to Ethereum have minimal impact on security while offering the potential to dramatically improve scalability. However, a newly discovered vulnerability could harm security, and the need for ZKP verification to validate blocks could result in increased centralization among blockchain validators.