{
 "item_id": "ker-nanoid_mask",
 "kernel": "nanoid_mask",
 "advisory": "RUSTSEC-2024-0343",
 "crate": "nano-id",
 "pre_version": "0.3.3",
 "post_version": "0.4.0",
 "advisory_url": null,
 "title": "Reduced entropy due to inadequate character set usage",
 "source_file": "src/lib.rs",
 "function": "alphabet_mask",
 "signature": "pub fn alphabet_mask(len: usize) -> usize",
 "spec_doc": "Bit mask used to index an alphabet of len symbols (len >= 2) from a random byte: the smallest all-ones value m with m >= len - 1, i.e. next_power_of_two(len) - 1.",
 "bug_class": "logic",
 "fidelity": "verbatim_logic",
 "extraction_note": "src/lib.rs MASK = $len - 1 is not a bit mask for non-power-of-two alphabets (biased/short alphabet)",
 "witness_args": "62usize",
 "labels": {
  "buggy": "nano-id@0.3.3",
  "reference": "nano-id@0.4.0"
 }
}