Public-Key Cryptography

Consensus-critical data is authenticated using ECDSA with the curves: Secp256k1 or Ed25519.

Secp256k1

The Secp256k1 key type is used by accounts that submit transactions to be included in Celestia.

Libraries

A highly-optimized library is available in C (https://github.com/bitcoin-core/secp256k1), with wrappers in Go (https://pkg.go.dev/github.com/ethereum/go-ethereum/crypto/secp256k1) and Rust (https://docs.rs/crate/secp256k1).

Public-keys

Secp256k1 public keys can be compressed to 257-bits (or 33 bytes) per the format described here.

Addresses

Cosmos addresses are 20 bytes in length.

Signatures

Deterministic signatures (RFC-6979) should be used when signing, but this is not enforced at the protocol level as it cannot be for Secp256k1 signatures.

Signatures are represented as the r and s (each 32 bytes) values of the signature. r and s take on their usual meaning (see: SEC 1, 4.1.3 Signing Operation). Signatures are encoded with protobuf as described here.

Human Readable Encoding

In front-ends addresses are prefixed with the Bech32 prefix celestia. For example, a valid address is celestia1kj39jkzqlr073t42am9d8pd40tgudc3e2kj9yf.

Ed25519

The Ed25519 key type is used by validators.

Libraries

• crypto/ed25519
• cometbft crypto/ed25519

Public Keys

Ed25519 public keys are 32 bytes in length. They often appear in validator configuration files (e.g. genesis.json) base64 encoded:

      "pub_key": {
        "type": "tendermint/PubKeyEd25519",
        "value": "DMEMMj1+thrkUCGocbvvKzXeaAtRslvX9MWtB+smuIA="
      }

Addresses

Ed25519 addresses are the first 20-bytes of the SHA256 hash of the raw 32-byte public key:

address = SHA256(pubkey)[:20]

Signatures

Ed25519 signatures are 64 bytes in length.