import { OnModuleDestroy } from '@nestjs/common';
import { IConfigOptions } from '../interface/config/options.interface';
/**
 * Utility class for encrypting and decrypting configuration values
 * Uses AES-256-GCM for encryption with authentication
 * @see {@link https://elsikora.com/docs/nestjs-crud-config/core-concepts/encryption | Core Concepts - Encryption}
 * @see {@link https://elsikora.com/docs/nestjs-crud-config/api-reference/utilities/crypto-utility | API Reference - CryptoUtility}
 */
export declare class CryptoUtility implements OnModuleDestroy {
    private currentEncryptionKey;
    private readonly DERIVED_KEY_CACHE;
    constructor(options?: IConfigOptions);
    /**
     * Decrypts a value encrypted with AES-256-GCM
     * @param {string} encryptedValue - The encrypted value in format: salt:iv:authTag:encryptedData (base64 encoded)
     * @param {string} encryptionKey - The encryption key
     * @returns {string} Decrypted value
     * @throws {Error} If decryption fails or authentication fails
     */
    decrypt(encryptedValue: string, encryptionKey: string): string;
    /**
     * Encrypts a value using AES-256-GCM
     * @param {string} value - The value to encrypt
     * @param {string} encryptionKey - The encryption key
     * @returns {string} Encrypted value in format: salt:iv:authTag:encryptedData (base64 encoded)
     */
    encrypt(value: string, encryptionKey: string): string;
    /**
     * Validates if a string is a valid encrypted value
     * @param {string} value - The value to check
     * @returns {boolean} True if the value appears to be encrypted
     */
    isEncryptedValue(value: string): boolean;
    /** Releases retained derived keys when the owning Nest module closes. */
    onModuleDestroy(): void;
    private clearKeys;
}