Hashavatar 0.7.0

[eldryoth]

hashavatar 0.7.0

hashavatar 0.7.0 starts the post-0.6 roadmap by making identity hashing explicit and extensible while keeping SHA-512 as the conservative default.

Highlights

• Added AvatarHashAlgorithm
• Added AvatarIdentityOptions
• Kept SHA-512 as the default identity hash
• Preserved the default SHA-512 identity preimage for existing callers
• Added optional BLAKE3 identity derivation behind the blake3 Cargo feature
• Added optional XXH3-128 identity derivation behind the xxh3 Cargo feature
• Added domain separation for non-default hash algorithms
• Added render, encode, and SVG entry points that accept identity hash options
• Added feature-gated tests for BLAKE3 and XXH3-128 rendering
• Hardened JPEG alpha flattening with wider arithmetic intermediates
• Hardened anti-aliased zero-length line drawing against NaN gradient propagation
• Added zeroize cleanup for derived identity digests and temporary identity hash preimage buffers
• Changed procedural cat RNG seeding to use 256 bits from the second half of the identity digest
• Added constant-time equality for AvatarIdentity
• Documented that rendering itself is not constant-time

Compatibility

• Existing callers that use AvatarIdentity::new, AvatarIdentity::new_with_namespace, render_avatar_for_id, render_avatar_for_namespace, render_avatar_svg_for_id, render_avatar_svg_for_namespace, encode_avatar_for_id, or encode_avatar_for_namespace continue to use SHA-512.
• Default SHA-512 rendering output is intended to remain stable from 0.6.0.
• BLAKE3 and XXH3-128 output is intentionally different from SHA-512 output.
• AvatarHashAlgorithm::Blake3 exists only when the blake3 feature is enabled.
• AvatarHashAlgorithm::Xxh3_128 exists only when the xxh3 feature is enabled.
• Cat-family output intentionally changes in 0.7.0 because procedural RNG
  seeding now uses a separate 256-bit digest slice instead of the low 64 bits
  that are also used by direct visual parameters.

Security And Quality

• SHA-512 remains the default for adversarial settings.
• BLAKE3 is provided by the upstream blake3 crate and uses dependency-provided acceleration where available.
• XXH3-128 is non-cryptographic and should only be used for non-adversarial identity distribution. Do not use it for adversarial or user-controlled identifiers unless the application first maps those identifiers through its own cryptographic boundary.
• All hash input components remain length-prefixed.
• Non-default algorithms include an explicit algorithm domain component.
• Oversized identity and namespace inputs are rejected before hashing for every enabled algorithm.
• Procedural RNG seeding uses 256 bits from the second half of the identity
  digest, separate from lower digest bytes used for direct visual parameters.
• Derived identity digests and temporary identity hash preimage buffers are zeroized when dropped.
• AvatarIdentity equality uses constant-time digest comparison.
• Rendering and encoding are intentionally variable-time operations. Shape
  counts, geometry, encoded size, and SVG length can vary with identity digest
  bytes, so callers should not treat rendering timing or output size as
  secret-preserving side channels.
• Tests cover parser round-trips, algorithm separation, optional feature paths, oversized input rejection, zero-length line drawing, JPEG alpha flattening, and zeroize trait coverage.

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This discussion was created from the release Hashavatar 0.7.0.