Expand description
§WHY2
WHY2 is a modern, high-performance symmetric encryption system designed for privacy-first applications where transparency and freedom are non-negotiable.
§What is WHY2?
WHY2 is a grid-based block cipher that organizes data into configurable 2D matrices of 64-bit cells. Unlike traditional table-based designs, it achieves nonlinearity through ARX operations (Add-Rotate-XOR), eliminating cache-timing vulnerabilities inherent to lookup table approaches.
The cipher uses a Substitution-Permutation Network structure with multiple rounds of mixing operations, combining nonlinear transformations with linear diffusion layers. Encryption is performed in Counter (CTR) mode, enabling parallel processing of multiple blocks.
§Key Characteristics
- Configurable Block Sizes: From 4×4 to 16×16 grids (1024-16384 bits per block)
- Cache-Timing Resistant: ARX-based design eliminates table lookups
- SIMD-Optimized: Vectorized operations for modern CPUs (AVX2, NEON)
- Constant-Time: All cryptographic operations avoid timing side-channels
- Memory-Safe: Pure Rust implementation prevents buffer overflows
- Parallel Encryption: CTR mode enables multi-core processing
§Design Philosophy
WHY2 draws from established cryptographic principles while introducing innovations suited for modern hardware:
- SPN Architecture: Proven approach used by standardized ciphers
- ARX Operations: Memory-hard-free construction (inspired by TEA/XTEA/Salsa20)
- Key-Dependent Transformations: Enhanced security through round-variant operations
- Native 64-bit Operations: Optimized for contemporary processor architectures
For detailed security architecture and implementation specifics, see the SECURITY documentation.
§Features
- Grid-based encryption with customizable dimensions
- ARX-style nonlinear mixing (cache-timing resistant)
- SIMD-accelerated operations (4× i64 vector processing)
- Round-key expansion via ChaCha20 CSPRNG
- Optional authenticated encryption (HMAC-SHA256)
- Constant-time implementation (via
subtlecrate) - Memory safety through Rust ownership system
- Automatic key material zeroization on drop
§Cargo Features
This crate allows selective enabling of components to keep the build lightweight.
-
auth(default): Enables theauthmodule for verifying data integrity and authenticity using an Encrypt-then-MAC scheme (HMAC-SHA256). -
constant-time(default): Enables constant-time comparison for cryptographic operations using thesubtlecrate. Disabling this may improve performance on non-sensitive data but opens the system to timing attacks. -
legacy: Enables the deprecated [legacy] module containing older, insecure versions of the encryption routines. This feature should only be used for migration or compatibility testing.
§Philosophy
- Privacy is a right, not a subscription feature.
- No government oversight: no telemetry, no backdoors, no metadata leakage.
- No payment required: encryption should be free as in freedom.
- Full transparency: all design decisions documented, all code auditable.
§Terminology
The codebase is organized to distinguish between the current implementation and deprecated versions:
- REX: Refers to the modern, secure implementation of the WHY2 algorithm.
These are the modules exposed directly at the crate root (e.g.,
encrypter,decrypter). Legacy: Refers to older, deprecated encryption routines found in the [legacy] module. These are retained for compatibility but are considered insecure.
§Examples
For comprehensive usage examples, including global algorithm usage and specific edge cases, please refer to the examples directory in the official repository.
§Security Disclaimer
WHY2 is an experimental encryption algorithm. While it draws inspiration from established designs like AES, it has not undergone formal cryptographic review or extensive academic analysis.
As such, it should not be considered suitable for high-assurance or production-grade cryptographic applications where proven security guarantees are required. Use at your own discretion, and always evaluate your threat model carefully.
§License
WHY2 is licensed under the GNU GPLv3. You are free to use, modify, and redistribute it under the terms of the license. See https://www.gnu.org/licenses/ for details.