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All cryptographic operations use constant-time implementations where applicable.

The Decoder requires explicit configuration:

// Verification is required by default
Decoder::new(qr_text)
    .verify_with_ed25519(&public_key)?
    .decode()?;

// To skip verification, you must explicitly opt out
Decoder::new(qr_text)
    .allow_unverified()
    .decode()?;

Default settings:

• Signature verification: required (must call allow_unverified() to skip)
• Timestamp validation: enabled
• Clock skew tolerance: 0 seconds
• Max decompressed size: 64KB

• Decompression limits: Configurable max_decompressed_bytes (default: 64KB) protects against zip bomb attacks
• CBOR depth limits: Maximum nesting depth of 128 prevents stack overflow attacks
• Timestamp validation: Credentials are validated against exp and nbf claims by default
• Algorithm enforcement: COSE messages must contain explicit algorithm headers

• Key zeroization: Signing and encryption keys are automatically zeroized on drop via the zeroize crate
• Weak key rejection: All-zeros keys and small-order Ed25519 points are rejected

AesGcmEncryptor::generate_nonce() is provided for convenience, but you are responsible for ensuring nonces are never reused with the same key. Nonce reuse with AES-GCM allows key recovery.

This library does not handle key distribution or trust establishment. You are responsible for:

• Secure key distribution and storage
• Certificate/key pinning and validation
• Key rotation and revocation

This library is designed to decode and verify Claim 169 QR codes where:

• The QR code content may be adversarially crafted
• The verifier has access to trusted issuer public keys

The library does NOT protect against:

• Key compromise at the issuer
• Replay of still-valid credentials (the library enforces exp/nbf by default, but does not provide anti-replay tracking)
• Side-channel attacks on the host system

cargo +nightly fuzz run fuzz_decode
cargo +nightly fuzz run fuzz_base45
cargo +nightly fuzz run fuzz_decompress

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