/**
 * @module node-opcua-secure-channel
 * Nonce tracking for replay detection.
 *
 * Nonces are stored in a Map with a timestamp. Entries older than
 * `ttlMs` are lazily evicted on each lookup. If the map still
 * exceeds `maxSize` after eviction, the oldest entries are dropped.
 *
 * This ensures bounded memory usage while preserving replay
 * detection within the configured time window.
 */
export type Nonce = Buffer;
/**
 * returns true if the nonce is null or zero (all bytes set to 0)
 */
export declare function isEmptyNonce(nonce: Nonce): boolean;
export declare function nonceAlreadyBeenUsed(nonce?: Nonce): boolean;
/**
 * Exposed for testing only – returns the underlying nonce Map.
 * @internal
 */
export declare function _getNonceStore(): Map<string, number>;
/**
 * Override TTL and maxSize for testing. Pass `undefined` to reset to defaults.
 * @internal
 */
export declare function _setNonceCacheParameters(ttlMs?: number, maxSize?: number): void;