Why Biometrics Don’t Belong on the Blockchain

Blockchain technology has brought incredible innovation to areas like supply chain, finance, and digital credentials—but when it comes to biometric authentication, blockchain is not the answer. Despite well-meaning attempts to combine the immutability of blockchain with the uniqueness of biometrics, the fundamental architecture of blockchain is incompatible with the way biometric systems actually work.

Here’s why.

1. Blockchain is for storage, not processing

At its core, blockchain is a distributed ledger—built to store data immutably, not to process or analyze it. You can store a hashed biometric template on-chain, but matching a user’s live biometric sample to that template can’t happen within the chain itself. The data must be brought off-chain to perform the match.

This creates a fundamental contradiction: if you need to move sensitive biometric data off the blockchain to do anything meaningful with it, you lose the privacy protections you were hoping to gain in the first place. The moment you extract it for processing, you introduce risk.

2. Sharding templates on the blockchain doesn’t solve the problem—especially in 1:N use cases

Some propose “sharding” biometric templates and distributing the pieces across a blockchain. But to authenticate, those shards must be decrypted and reassembled off-chain. That process is not only time-consuming and computationally intensive, but it also introduces inaccuracy because the pieces may not line up exactly when they are reassembled—a non-starter for biometric systems that demand precision.

In 1:N (one-to-many) scenarios, like deduplication or watchlist searches, it’s even worse. Every single biometric template would need to be pulled off-chain for matching. This completely undermines the idea of decentralized security and creates massive latency and vulnerability.

3. The cost of blockchain is prohibitive

Public blockchains, in particular, are expensive. Every write operation carries a “gas” fee, and biometric authentication requires frequent and dynamic operations, not just storing a hash once and walking away. Imagine paying a fee every time someone logs in with their fingerprint or face. It’s not just impractical, it’s financially unsustainable at scale.

4. Blockchains are public by design—biometrics are not

Even if you hash or encrypt biometric data before putting it on a blockchain, the public nature of many blockchain environments makes this risky. Encryption methods can become obsolete, and hashes can be reverse-engineered with enough time and computing power. Biometrics are inherently sensitive—you can’t change your face or voice the way you can change a password.

While identity tokens or proofs (like those used in verifiable credentials) can be safely anchored on-chain, storing actual biometric data or templates is a serious security and privacy concern.

5. Biometrics on the blockchain is not compliant with data protection laws

Laws like GDPR, DPDP, PIPEDA and others around the world require data to be deleted upon request. That’s a problem for blockchain. Once data is written to the chain, it’s immutable—which is great for audit trails, but not great for privacy rights. You simply cannot guarantee a user’s “right to be forgotten” if their biometric data, or even a hashed reference to it, is permanently etched into the chain.

The bottom line

Putting biometrics on the blockchain might sound like a good idea—but when you unpack the technical, regulatory, and operational realities, it just doesn’t work. The answer isn’t forcing biometrics into a blockchain-shaped box. It’s rethinking how we protect, process, and match biometric data—without compromising privacy, performance, or compliance.

How Anonybit Works—and Why It’s Different

Anonybit takes a fundamentally different approach. Instead of storing biometric templates in a centralized location or on a public ledger, Anonybit breaks the biometric template into encrypted, anonymized bits and distributes them across a distributed, multi-party cloud environment. The template is never reconstructed, even during the matching process.

The technique uses a patented application of biometrics into multi-party computation (MPC) and zero knowledge proofs, producing a result without ever requiring the original biometric sample or exposing or revealing the biometric data itself. This is true privacy-by-design: no honeypots, no static hashes, no risk of reverse-engineering, and no need to reassemble anything.

Unlike blockchain, which locks data in an immutable ledger, Anonybit’s architecture allows for revocation, deletion, and dynamic control, key requirements for compliance with data protection laws. It’s purpose-built for secure, scalable biometric authentication that respects privacy from the ground up.

Use Cases For Anonybit In Supporting Blockchain Applications

While blockchain isn’t suitable for storing or matching biometrics, Anonybit seamlessly complements blockchain-based identity ecosystems.

Our privacy-preserving infrastructure enables biometric matching off-chain, without ever reconstructing the biometric template. Using multi-party computation (MPC) and zero knowledge proofs, Anonybit keeps data decentralized and protected, allowing the biometric to serve as a secure binding mechanism to digital credentials, wallets, and identity tokens.

Here’s how we fit in:

• Biometric binding to tokens or verifiable credentials: Anonybit enables users to prove they are the rightful holder of a token or verifiable credential—without exposing their biometric or storing it on-chain.
• Proof of presence and intent: For agent-based commerce, DAO voting, or blockchain transaction signing, we provide cryptographic proof that the human behind the transaction is real and present.
• Immutable integrity checks: While we don’t store biometrics on-chain, blockchain can be used to anchor integrity hashes or proof of enrollment that verify a biometric hasn’t been altered.

Anonybit is building the connective tissue between the human identity and the digital credential—bridging trust gaps without exposing sensitive data or compromising decentralization principles.

In short: Biometrics require specialized infrastructure—blockchain isn’t the answer. Anonybit secures the biometrics and connects the rest of the identity ecosystem.

Summary: Frequently Asked Questions (FAQ)

Can biometric data be stored on the blockchain?

While technically possible, storing biometric data—even in hashed or encrypted form—on the blockchain introduces major security, privacy, and compliance risks. Blockchain’s immutability prevents deletion, violating laws like GDPR that guarantee a right to be forgotten.

Why isn’t blockchain suitable for biometric authentication?

Blockchain is built for immutable storage, not real-time processing or analysis. Biometric authentication requires live matching of biometric samples, which must occur off-chain—defeating the purpose of on-chain protection and exposing sensitive data during the process.

Is using sharded biometric templates on the blockchain secure?

No. Sharding templates and reassembling them off-chain introduces latency, vulnerability, and potential inaccuracies—especially in 1:N use cases like deduplication or watchlist matching. It also violates the principles of true decentralization.

What makes Anonybit different from blockchain-based biometric solutions?

Anonybit doesn’t store or reconstruct biometric templates. Instead, it uses multi-party computation (MPC) and zero knowledge proofs to match encrypted data without exposing the biometric—enabling biometric authentication that is privacy-preserving and GDPR-compliant.

How can Anonybit support blockchain identity applications?

Anonybit enables secure off-chain biometric matching while anchoring cryptographic proofs to blockchain systems. This allows users to prove presence, intent, or credential ownership—without ever storing biometric data on-chain.