spark-nacl
A formally verified, portable SPARK 2014 implementation of the NaCl cryptographic library with constant-time algorithms.
What is spark-nacl?
SPARKNaCl is a cryptographic library that reimplements the TweetNaCl API using the SPARK 2014 programming language. It provides authenticated encryption, digital signatures, and hashing with the added guarantee of formal verification for type safety and correctness. The project solves the need for high-assurance cryptography that is both portable and resistant to timing attacks.
Developers and organizations requiring formally verified cryptographic implementations for safety-critical systems, embedded devices, or high-security applications where proof of correctness is essential.
Developers choose SPARKNaCl for its unique combination of automated formal verification, constant-time algorithms, and zero-footprint portability, offering higher assurance than typical C-based cryptographic libraries while maintaining compatibility with the NaCl API.
Overview
SPARK 2014 re-implementation of the TweetNaCl crypto library
Use Cases
Best For
- Building high-assurance systems requiring formally verified cryptography
- Embedded and bare-metal applications needing zero-footprint cryptographic libraries
- Implementing timing-attack-resistant cryptographic operations
- Educational projects exploring formal methods in security-critical code
- Extending cryptographic support with verified ChaCha20 and SHA-256 implementations
- Porting NaCl-based cryptography to platforms without C runtime dependencies
Not Ideal For
- Projects in languages other than Ada or C without willingness to interface with SPARK tooling
- Rapid prototyping or applications where the overhead of formal verification is unnecessary
- Teams needing a broad range of cryptographic algorithms beyond NaCl's core and its ChaCha20/SHA-256 extensions
- Environments without access to or familiarity with GNAT and SPARK verification tools
Pros & Cons
Pros
The entire library has an automated static proof of type safety and correctness using SPARK 2014 tools, ensuring no buffer overflows, numeric overflows, or runtime errors as confirmed in the README's proof results.
Retains timing-attack-resistant implementations from NaCl, with code structured to avoid conditional statements on sensitive data, maintaining security against side-channel attacks.
Compatible with the GNAT Zero Footprint runtime, enabling deployment on bare-metal embedded systems up to servers without runtime dependencies, as highlighted in the Goals section.
Includes ChaCha20, SHA-256, HMAC, HKDF, and AEAD algorithms beyond the original NaCl specification, moving towards TLS 1.3 support as noted in the June 2022 updates.
Features extensive explanatory comments and contracts, making it more understandable than minimal implementations like TweetNaCl, as emphasized in the README's philosophy.
Cons
Written in SPARK/Ada, which has a smaller community and tooling; a C API wrapper is a known TBD item, complicating integration with non-Ada projects.
Requires specific GNAT and SPARK tools for development and verification, adding setup complexity and limiting use in environments without these tools.
Performance optimization for Salsa20 and some primitives is still on the 'to be done' list, and performance can vary significantly with compiler optimization levels (e.g., slower at -O0).
The PRNG package was removed for portability, forcing clients to supply their own secure random number generator, increasing implementation effort as noted in the March 2021 updates.
Frequently Asked Questions
Related Projects
ada-crypto-libraryThis project is obsolete is no longer developed, maintained or serviced!
libkeccakSHA-3 and other Keccak related algorithms in SPARK/Ada.
libsparkcryptoA cryptographic library in SPARK 2014
libsodium-adalibsodium for Ada - A secure cryptographic library
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