Digital signatures all prove the same core claim, “this specific key authorized this exact message,” but the algorithms differ in what they enable at scale. ECDSA, Ed25519, Schnorr, and BLS each balance security, size, performance, and protocol features in distinct ways. Chia Network chose BLS because it unlocks capabilities that make blockchains leaner, simpler, and more programmable.
The Baseline
ECDSA, standardized in NIST’s Digital Signature Standard, is the battle‑tested workhorse behind Bitcoin and much of Web2 PKI. It’s secure when implemented correctly but offers no native aggregation or non‑interactive multisignatures; each signer adds a separate signature that validators must process individually. Ed25519, specified in RFC 8032, improves ergonomics: deterministic signing removes nonce pitfalls, verification is fast, and the Edwards curve structure simplifies constant‑time implementations. Still, like ECDSA, Ed25519 does not natively provide non‑interactive aggregates or threshold signatures without heavier protocols.
Schnorr bridges that gap. In Bitcoin, BIP‑340 standardizes a Schnorr variant over secp256k1, enabling elegant multisignatures that look like one signature on‑chain. With modern constructions like MuSig2, participants can produce a single joint signature with minimal rounds and strong security against nonce misuse and rogue‑key attacks. This is a huge win over ECDSA for multi‑party control. The tradeoff: even the best Schnorr multisig needs at least some interaction between signers per message, which complicates asynchronous workflows, cross organizational signing, and large validator sets.
Onto BLS
Boneh–Lynn–Shacham (BLS) takes a different path. Built on bilinear pairings, it delivers short, deterministic signatures and crucially non‑interactive aggregation. Any set of valid BLS signatures on the same message can be added into a single signature that verifies as if one party signed. Even better, BLS can aggregate across distinct messages with simple proofs of possession (PoP) to defeat rogue‑key attacks (Boneh–Lynn–Shacham 2001; IETF CFRG draft BLS; PoP guidance in the draft). In practice, this lets a mempool or a block producer collapse dozens or thousands of signatures down to one, massively reducing bandwidth and disk footprint, while keeping verification straightforward via multi‑pairing checks and a single final exponentiation (RFC 9380 Hash‑to‑Curve underpins safe hashing for BLS12‑381).
Compare and Contrast
What does that enable that others can’t match as cleanly? First, constant‑size aggregates. In ECDSA or Ed25519, more signers or more inputs mean more signatures. In Schnorr, you can achieve a single on‑chain signature, but you must coordinate per‑message. With BLS, a block assembler can non‑interactively combine signatures as they arrive. Chia leans on this to keep transactions compact and validation light: spend bundles contain BLS signatures that the network readily aggregates, minimizing overhead even under high load with flexible multi‑key semantics. BLS supports simple public‑key aggregation and clean threshold designs (via Shamir shares or DKG), so “m‑of‑n” control reduces to one signature with straightforward verification logic, no script bloat, no per‑message rounds.
There are performance nuances. A single BLS verification is slower than a single Ed25519 verify, and pairings are mathematically heavier than Edwards or Weierstrass scalar multiplies. But system‑level performance is what matters. When you can compress hundreds of signatures into one and verify them together, the amortized cost per authorization drops dramatically. Distinct‑message batch verification is also natural in BLS using multi‑pairings with PoP, while keeping soundness tight under standard assumptions. For blockchains, where signature count dominates block size and validation time, BLS’s asymptotics win.
Security posture is equally strong. Determinism eliminates nonce‑reuse catastrophes familiar from ECDSA. Signature malleability is not an issue in properly specified BLS. The IETF effort standardizes safe ciphersuites, subgroup checks, and domain separation for curves like BLS12‑381, reducing implementation foot‑guns and ensuring cross‑vendor interoperability (pairing‑friendly curves draft; RFC 9380). And while Schnorr with MuSig2 provides excellent multi‑party security, BLS’s ability to aggregate non‑interactively across many parties and messages with succinct PoP keeps complexity out of the critical path.
Feature‑wise, the comparison is stark: ECDSA is proven and ubiquitous but feature‑limited; Ed25519 is fast and safe to implement but similarly constrained; Schnorr brings elegant multisig with interaction; BLS delivers constant‑size aggregation, simple thresholding, public‑key aggregation, and deterministic, short signatures, all with clean verification. That is why protocols prioritizing scalability and clean application logic, like Chia, have standardized on BLS for the signature layer. The net effect is smaller blocks, faster sync, cheaper validation, and simpler wallet and contract code paths that don’t need bespoke “scripts” just to combine authorizations
Does that mean BLS is always the fastest primitive? No and it doesn’t need to be. When you optimize for systems where signature count dwarfs everything else, the ability to compress and verify in aggregates dominates micro‑benchmarks. That’s the world of modern blockchains. In that world, BLS is best not as a slogan, but because its algebra gives you the features your protocol actually needs, without contortions.
Sources: Boneh–Lynn–Shacham 2001; IETF CFRG draft: BLS Signatures; RFC 8032 (Ed25519); FIPS 186‑5 (ECDSA); BIP‑340 (Schnorr); MuSig2 (ePrint 2020/1261); RFC 9380 (Hash to Curve); Chia: Aggregated Signatures.