/**
 * Shannon entropy calculation for detecting high-entropy strings
 * that may be secrets (API keys, tokens, passwords, etc.)
 *
 * Entropy measures the randomness/unpredictability of a string.
 * Higher entropy = more random = more likely to be a secret.
 */
/**
 * Minimum string length to consider for entropy analysis.
 * Shorter strings don't have enough data for meaningful entropy calculation.
 */
export declare const MIN_LENGTH_FOR_ENTROPY = 16;
/**
 * High entropy threshold (bits per character).
 * Typical thresholds:
 * - English text: ~1.0-1.5 bits/char
 * - Base64 encoded: ~5.5-6.0 bits/char
 * - Random alphanumeric: ~5.0-5.5 bits/char
 * - Pure random bytes: ~8.0 bits/char (max)
 *
 * We use 4.5 as a threshold to catch most secrets while avoiding
 * too many false positives on normal text.
 */
export declare const HIGH_ENTROPY_THRESHOLD = 4.5;
/**
 * Strict entropy threshold for --strict mode.
 * Lower threshold means more things get flagged.
 */
export declare const STRICT_ENTROPY_THRESHOLD = 4;
/**
 * Calculate Shannon entropy of a string.
 *
 * Shannon entropy measures the average number of bits needed to encode
 * each character based on its frequency distribution.
 *
 * @param str - The string to analyze
 * @returns Entropy in bits per character
 */
export declare const calculateEntropy: (str: string) => number;
/**
 * Check if a string has characteristics of a secret based on entropy
 * and other heuristics.
 *
 * @param value - The string to check
 * @param strictMode - If true, use stricter (lower) threshold
 * @returns True if the string looks like a potential secret
 */
export declare const isPossibleSecretByEntropy: (value: string, strictMode?: boolean) => boolean;
/**
 * Get entropy level description for human-readable output
 */
export declare const getEntropyLevel: (entropy: number) => string;