A BLS digital signature, also known as Boneh–Lynn–Shacham[1] (BLS), is a cryptographicsignature scheme which allows a user to verify that a signer is authentic.
The scheme uses a bilinear pairing for verification, and signatures are elements of an elliptic curve group. Working in an elliptic curve group provides some defense against index calculus attacks (with the caveat that such attacks are still possible in the target group of the pairing), allowing shorter signatures than FDH signatures for a similar level of security.
Unique and deterministic: for a given key and message, there is only one valid signature (like RSA PKCS1 v1.5, EdDSA and unlike RSA PSS, DSA, ECDSA and Schnorr).[3]
Signature Aggregation: Multiple signatures generated under multiple public keys for multiple messages can be aggregated into a single signature.[4]
BLS12-381 is part of a family of elliptic curves named after Barreto, Lynn, and Scott[7] (a different BLS trio, except for the L). Designed by Sean Bowe in early 2017 as the foundation for an upgrade to the Zcash protocol. It is both pairing-friendly (making it efficient for digital signatures) and effective for constructing zkSnarks.[8] The usage of BLS12-381 for BLS signatures is detailed in the IETF internet draft[9]
By 2020, BLS signatures were used extensively in version 2 (Eth2) of the Ethereumblockchain, as specified in the IETF draft BLS signature specification—for cryptographically assuring that a specific Eth2 validator has actually verified a particular transaction.[2] The use of BLS signatures in Ethereum is considered a solution to the verification bottleneck only for the medium term, as BLS signatures are not quantum secure. Over the longer term—say, 2025–2030—STARK aggregation is expected to be a drop-in replacement for BLS aggregation.[9][12]
Dfinity (developers of the "Internet Computer" cryptocurrency) uses a BLS implementation.[13]