lib-sha2

Minimal no_std SHA-2 implementation crate for EriX.

This crate provides both:

• SHA-256 (boot image hashing, section hashing)
• SHA-512 (Ed25519 prehash requirements and related consumers)

UEFI + x86_64 are current primary targets, but this crate is explicitly portable and architecture-neutral.

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Scope

This crate provides:

• incremental and one-shot SHA-256 API
• incremental and one-shot SHA-512 API
• deterministic digest outputs in fixed-size arrays

This crate does not provide:

• HMAC or HKDF
• SHA-3/BLAKE variants
• signature verification
• key management or RNG

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Why one crate for both algorithms

EriX needs both SHA-256 and SHA-512 in the secure boot chain:

• SHA-256 for boot.img manifest and section verification
• SHA-512 for Ed25519 verification support

Keeping both in one crate ensures:

• shared implementation standards (no external deps, no_std)
• consistent testing and review posture
• less duplicated low-level logic

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Design constraints

• #![no_std]
• zero external dependencies
• deterministic behavior
• explicit APIs and minimal unsafe (ideally none)

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Intended consumers

• lib-bootimg (SHA-256)
• lib-ed25519 (SHA-512)
• bootloader and future kernel/user-space verifiers

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Status

Implemented baseline.

SHA-256 and SHA-512 one-shot/incremental APIs are available and covered by unit tests. Remaining work is hardening and expanded cross-repo regression coverage.

See ARCHITECTURE.md and ROADMAP.md.