/**
 * Case-insensitive lookup table for certificate-related entries.
 *
 * @private
 */
export declare class _PdfCertificateTable {
    private _orig;
    private _keys;
    constructor();
    /**
     * Return all original keys currently stored in the table.
     *
     * @private
     * @returns {string[]} Array of stored keys.
     */
    _getKeys(): string[];
    /**
     * Clears all stored entries from both the original map and the internal key map.
     *
     * @private
     * @returns {void} nothing.
     */
    _clear(): void;
    /**
     * Remove an entry by key (case-insensitive) and return its value.
     *
     * @private
     * @param {string} key - Key of the entry to remove.
     * @returns {any} The removed value or null when not found.
     */
    _remove(key: string): any;
    /**
     * Retrieve a value by key (case-insensitive).
     *
     * @private
     * @param {string} key - Lookup key.
     * @returns {any} The stored value or null if missing.
     */
    _get(key: string): any;
    /**
     * Set or replace a value for the given key (case-insensitive).
     *
     * @private
     * @param {string} key - The key to set.
     * @param {any} value - The value to associate with the key.
     * @returns {void}
     */
    _setValue(key: string, value: any): void;
}