/**
 * Tokens no transform may touch: identifiers, credentials, hashes.
 *
 * WHAT THIS EXISTS FOR, measured before it was written. The log templater
 * builds its grouping shape by replacing every digit run with a placeholder,
 * and digit runs occur INSIDE identifiers. On a line carrying a correlation id
 * and an API key it produced:
 *
 *   #-#-#T#:#:#Z INFO request #f#a#c#-#b#d-#e#-#a#-ffedcba# authorised with
 *   sk-ant-api#-QmFzZTY#TG#va#luZ#NlY#JldFZhbHVlSGVy
 *
 * That is not an elision, it is CORRUPTION. The original was
 * `3f2a9c14-8b7d-4e56-9a01-ffedcba98765`, and what survives looks enough like
 * an identifier that a model may quote it back or search for it. A dropped
 * value is visibly missing; a shredded one is invisibly wrong, which is worse.
 *
 * HeadRoom's masks.py carries the same idea and names the same threshold: a
 * length floor of 20, because "normalized Shannon entropy alone cannot tell a
 * 40-char API key from an 8-char diverse word", matching what trufflehog and
 * detect-secrets use. That floor is adopted here for the same reason.
 *
 * NOT A SECRET SCANNER. The goal is not to find every credential -- it is to
 * stop our own transforms mangling anything that looks like an identifier a
 * reader might need verbatim. False positives cost a few tokens; false
 * negatives corrupt data.
 */
/** Shannon entropy in bits per character. */
export declare function entropy(value: string): number;
/**
 * Is this token dense enough, and long enough, to be a credential?
 *
 * The length floor does the work the entropy score cannot: `password` has
 * respectable entropy per character and is plainly not a key, while a
 * forty-character base64 run is one whatever it spells.
 */
export declare function isSecretLike(token: string): boolean;
/**
 * Character ranges in `text` that must survive any transform, merged and
 * sorted.
 *
 * Ranges rather than tokens because callers need to ask "does this match
 * overlap something protected", which is a position question.
 */
export declare function structuralRanges(text: string): Array<[number, number]>;
/** Does [start, end) touch anything protected? */
export declare function overlapsStructural(ranges: readonly (readonly [number, number])[], start: number, end: number): boolean;
/** Does this passage carry an identifier or credential at all? */
export declare function containsStructural(text: string): boolean;
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