fastcrypto

fastcrypto is a common cryptography library used in software at Mysten Labs. It is a Cargo workspace containing the crates fastcrypto, fastcrypto-derive, fastcrypto-tbls, fastcrypto-zkp, fastcrypto-vdf, fastcrypto-pq and fastcrypto-cli. Most of them are published as independent crates to encourage reusability across different applications and domains; fastcrypto-pq is not yet published.

fastcrypto is a wrapper library around several carefully selected crates with the following considerations:

• Security: Whether the libraries are vulnerable to known attack vectors or possible misuses.
• Performance: Whether the crate performs cryptographic operations with speed after extensive benchmarking. This is critical for the Sui Network to be performant when signing and verifying large amounts of transactions and certificates.
• Determinism: Whether the signature is non-malleable.
• Popularity: Whether the library is used by other consensus critical systems.

Furthermore, we extend the selected libraries with additional features:

• Robust testing framework: Wycheproof tests and prop tests are added when possible to protect against arbitrary inputs and crafted edge cases.
• Zeroization: Sensitive private key materials are cleared from memory when it goes out of scope using the zeroize trait. Note that this is best effort and does not guarantee that all sensitive data is cleared from memory as data may be copied or moved around by the compiler, FFI, etc.
• Serialization: Effective and standardized serialization are required.

This library will be continuously updated with more schemes and faster implementations based on benchmarking results, RFC updates, new research and auditor inputs.

Some modules are gated behind the experimental feature flag. These have not been audited and should not be relied on in production.

fastcrypto

The fastcrypto crate contains:

• Traits that should be implemented by concrete types representing digital cryptographic materials.

  • [SigningKey]: Trait implemented by the private key with associated types of its public key and signature.
  • [VerifyingKey]: Trait implemented by the public key with associated types of its private key and signature. It also includes a default implementation of batch verification that fails on empty batch verification.
  • [Authenticator]: Trait implemented by the signature with associated types of its public key and private key.
  • [AggregateAuthenticator]: Trait implemented by the aggregated signature, which allows adding signatures to the aggregated signature and verifying against the public keys with the corresponding messages.
  • [KeyPair]: Trait that represents a public/private keypair, which includes the common get priv/pub key functions and a keypair generation function with seeded randomness.
  • [ToFromBytes]: Trait that aims to minimize the number of steps involved in obtaining a serializable key.
  • [EncodeDecodeBase64]: Trait that extends ToFromBytes for immediate conversion to/from Base64 strings. This is the format in which cryptographic materials are stored.

• Concrete signature schemes of type that implement the recommended traits required for cryptographic agility.

  • Ed25519: Backed by ed25519-consensus crate. Compliant to ZIP-215 that defines the signature validity that is lacking from RFC8032 but critical for consensus algorithms. ed25519-dalek is fully deprecated due to the recently discovered Chalkias double pub-key api vulnerability.
  • Secp256k1: ECDSA signatures over the secp256k1 curve. Backed by Secp256k1 FFI wrapper that binds to C library and provides performance faster than the native Rust implementation k256 library by ~30% on verification. Produces either a standard ECDSA signature or a 65-byte recoverable signature of shape [r, s, v] where v can be 0 or 1 representing the recovery Id. Produces deterministic signatures using the pseudo-random deterministic nonce generation according to RFC6979, without the strong requirement to generate randomness for nonce protection. Uses sha256 as the default hash function for sign and verify. An interface for verify_hashed is provided to accept a pre-hashed message and its signature for verification. Supports public key recovery by providing the Secp256k1 recoverable signature with the corresponding pre-hashed message. An accepted signature must have its s in the lower half of the curve order. If s is too high, normalize s to order - s where curve order is 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141. See more at BIP-0062.
  • Secp256r1: ECDSA signatures over the secp256r1 curve backed by the p256 crate which is a pure rust implementation of the Secp256r1 (aka NIST P-256 and prime256v1) curve. The functionality from p256 is extended such that, besides standard ECDSA signatures, our implementation can also produce and verify 65 byte recoverable signatures of the form [r, s, v] where v is the recoveryID. Signatures are produced deterministically using the pseudo-random deterministic nonce generation according to RFC6979, without the strong requirement to generate randomness for nonce protection. Uses sha256 as the default hash function for sign and verify. Supports public key recovery by providing the Secp256r1 ECDSA recoverable signature with the corresponding pre-hashed message. An accepted signature must have its s in the lower half of the curve order. If s is too high, normalize s to order - s where curve order is 0xFFFFFFFF00000000FFFFFFFFFFFFFFFFBCE6FAADA7179E84F3B9CAC2FC632551 defined here.
  • BLS12-381: Backed by blst crate written in Assembly and C that optimizes for performance and security. G1 and G2 points are serialized following ZCash specification in compressed format. Provides functions for verifying signatures in the G1 group against public keys in the G2 group (min-sig) or vice versa (min-pk). Provides functions for aggregating signatures and fast verifying aggregated signatures, where public keys are assumed to be verified for proof of possession.
  • RSA: Backed by crate rsa. Provides verification of RSASSA-PKCS1-v1_5 signatures using SHA-256 according to RFC 8017, from either a DER encoded public key or raw modulus and exponent. Signing is not provided.

• Group arithmetic over the elliptic curves used by the schemes above, exposed through the [GroupElement] and [Scalar] traits in the groups module. Implementations are available for BLS12-381 (G1, G2 and GT, including pairings), Ristretto255, secp256k1 and secp256r1. The groups::multiplier module provides windowed and BGMW scalar multiplication with precomputation, along with traits for multi-scalar multiplication.

• Utility functions on cryptographic primitives. Some of them serve as the Rust implementation of the Move smart contract API in Sui.

  • HKDF: An HMAC-based key derivation function based on RFC-5869, to derive keypairs with a salt and an optional domain for the given keypair. This requires choosing an HMAC function that expands precisely to the byte length of a private key for the chosen KeyPair parameter.
  • Pedersen Commitment: Function to create a Pedersen commitment with a value and a blinding factor. Add or subtract Ristretto points that represent Pedersen commitments.
  • Bulletproofs Range Proof: Function to prove that a committed value is an unsigned integer that is within the range [0, 2^bits). Function to verify that the commitment is a Pedersen commitment of some value with an unsigned bit length, a value is an integer within the range [0, 2^bits).
  • Bulletproofs++ Range Proof (experimental): A shorter range proof over Ristretto255 supporting batches of commitments and bit sizes 8, 16, 32 and 64. See the module README for details.
  • Elliptic Curve VRF (ECVRF): A verifiable random function implementation using the Ristretto255 group. Function to create a proof based on a given input and verify a proof for a given output, based on specification in draft-irtf-cfrg-vrf-15.
  • Twisted ElGamal: Encryption over Ristretto255 with sigma protocols proving that a ciphertext is well-formed, plus a verifiable key encapsulation that encrypts a private key to multiple recipients and proves consistency with the sender's public key.
  • NIZK: A non-interactive zero-knowledge proof of knowledge for a DDH tuple (G, H, xG, xH), made non-interactive with the Fiat-Shamir transform.
  • Merkle tree: A simple binary Merkle tree with both inclusion and non-inclusion proofs.
  • AWS Nitro attestation: Verification of AWS Nitro enclave attestation documents, covering COSE_Sign1 parsing, attestation document validation and certificate chain verification against the AWS Nitro root of trust. Enabled by default; the root certificate is bundled with the crate.
  • JWT: Parsing and validation of the JWT claims used by zkLogin.

• Symmetric encryption (aes feature): AES in CTR, CBC (with PKCS7, ISO 10126 and ANSI X9.23 padding), GCM and GCM-SIV modes, for 128, 192 and 256 bit keys where applicable.

• Encoding: Base64, Hex, Base58 and Bech32 are defined with an encoding trait with its customized serialization and validations, backed by base64ct, hex, bs58 and bech32. Notably, the base64ct crate has been chosen instead of the most popular base64 Rust crate, because (a) it is constant time and (b) mangled encodings are explicitly rejected to prevent malleability attacks when decoding, see paper on in-depth analysis.

• Hash functions wrappers: SHA2_256 with 256 bit digests, SHA3_256 with 256 bit digests, SHA2_512 with 512 bit digests, SHA3_512 with 512 bit digests, KECCAK with 256 bit digests, BLAKE2-256 with 256 bit digests.

• Multiset Hash: A hash function where the output of the hash function is a point on the elliptic curve. It also allows for efficient computation for the hash of the union of two multiset.

• An asynchronous signature service is provided for testing and benchmarking.

Feature flags

Flag	Effect
aes	Include AES and its modes.
copy_key	Allow private keys to be copied.
experimental	Include modules that have not been audited.
wasm	Required when targeting wasm32.

Other crates

The fastcrypto-zkp crate contains APIs to verify a Groth16 proof along with its prepared verifying key and public inputs. BN254 and BLS12381 curves are supported. The verifier is backed by Arkworks and blst libraries. It also contains the zkLogin verifier used by Sui, including parsing and validation of zkLogin proofs and address derivation, and a Poseidon hash implementation over the BN254 scalar field.

The fastcrypto-tbls crate implements threshold BLS signatures and distributed key generation. It contains Shamir secret sharing over polynomials, ECIES encryption, a weighted node set with knapsack-based weight reduction, a random oracle, the discrete-log NIZKs used by the protocols, and a threshold Schnorr protocol built on asynchronous verifiable secret sharing with presigning and signing.

The fastcrypto-vdf crate implements verifiable delay functions. It contains the Wesolowski and Pietrzak VDF constructions, imaginary class groups and RSA groups as the underlying groups of unknown order, hash-to-group and discriminant generation, and the supporting number-theoretic routines. The entire crate is gated behind its own experimental feature flag and has not been audited.

The fastcrypto-pq crate implements post-quantum signature schemes: ML-DSA-65 (FIPS 204) behind fastcrypto's traits, backed by the formally verified mldsa-native C implementation, and SLH-DSA (FIPS 205) building blocks in pure Rust. It is not published and has not been audited. See the crate README.

The fastcrypto-derive crate provides the SilentDisplay and SilentDebug derive macros, which keep private key material out of formatted output, and GroupOpsExtend, which expands a group element's Add, Sub, Neg and scalar Mul implementations to cover all borrowed and owned argument combinations plus the assigning variants.

The fastcrypto-cli crate includes CLI tools available for debugging. See usages with -h flag.

$ cargo build --bin encode-cli
$ target/debug/encode-cli -h
$ cargo build --bin sigs-cli
$ target/debug/sigs-cli -h
$ cargo build --bin ecvrf-cli
$ target/debug/ecvrf-cli -h
$ cargo build --bin vdf-cli
$ target/debug/vdf-cli -h
$ cargo build --bin tlock-cli
$ target/debug/tlock-cli -h

WASM

The fastcrypto crate can be used when building WASM modules. To do this, enable the wasm feature flag when including the fastcrypto crate in your Cargo.toml file and follow the instructions found in the Rust and WASM book to build the WASM module. Note that fastcrypto-pq depends on a C toolchain and does not build for wasm32.

Tests

There exist unit tests for all primitives in all crates, which can be run by:

$ cargo test

Benchmarks

In fastcrypto, one can compare all currently implemented signature schemes for sign, verify, verify_batch and key-generation by running:

$ cargo bench

A report of the benchmarks is generated for each release, allowing easy comparison of the performance of the different cryptographic primitives and schemes available in fastcrypto. As an example, we get these timings for signing messages and verifying the signature for the different schemes in fastcrypto as of revision dd5adb:

Below is another plot made using data from the benchmark report, showing benchmarks for batched signature verification where all signatures are on the same message:

The other crates carry their own benchmarks, which are run the same way from the crate directory. In fastcrypto-zkp, for example, benchmarks can be run for Arkworks to blst representation of field elements, and for verifying Groth16 in BN254 and BLS12381:

$ cd fastcrypto-zkp/
$ cargo bench

License

All crates licensed under either of

• Apache License, Version 2.0
• MIT license