Cryptography

The Pactus blockchain uses various cryptographic algorithms, including hashing and digital signature schemes, to protect user data and secure transactions.

Hashing Algorithm

Pactus uses the Blake2b hashing algorithm. Blake2b is a fast and secure cryptographic hash function that produces unique digital fingerprints of data.

Signature Schemes

Pactus supports several signature schemes for different purposes.

BLS Signatures

BLS (Boneh–Lynn–Shacham) is the primary signature scheme used by validators and BLS-based accounts. BLS public keys are 96 bytes and use the G2 subgroup of the BLS12-381 curve. BLS is a threshold signature scheme with two notable properties:

Signature Aggregation

BLS signatures can be aggregated — multiple individual signatures can be combined into a single signature without increasing the overall size. This is useful for consensus where many validators sign the same message.

Non-Malleability

BLS signatures are non-malleable: it is impossible to produce two different valid signatures for the same message. Each message has exactly one valid signature.

Ed25519 Signatures

Ed25519 is supported for account addresses (see PIP-52). Ed25519 provides strong security with compact 32-byte public keys and fast performance. Ed25519 account addresses start with pc1r....

secp256k1 Signatures

secp256k1 (ECDSA) is supported for account addresses (see PIP-53). This is the same curve used by Bitcoin, with 33-byte compressed public keys, enabling compatibility with existing wallet tools. secp256k1 account addresses start with pc1y....

Address Types

Addresses in Pactus include a type that indicates their intended usage (see PIP-8):

HD Key Derivation

Pactus supports Hierarchical Deterministic (HD) key derivation for wallets. This allows a single master seed to generate a tree of keys in a predictable way.

BLS HD derivation follows PIP-11, which defines a standard for BLS12-381 HD key chains based on BIP-0032. Ed25519 and secp256k1 HD derivation follow SLIP-10.