/**
 * Configuration options for TOTP setup
 */
export interface TOTPConfig {
    /** The issuer name (e.g., "BrightChain") */
    issuer: string;
    /** The account label (e.g., user email) */
    label: string;
    /** Hash algorithm - defaults to SHA1 for compatibility */
    algorithm?: 'SHA1' | 'SHA256' | 'SHA512';
    /** Number of digits in the code - defaults to 6 */
    digits?: number;
    /** Time period in seconds - defaults to 30 */
    period?: number;
}
/**
 * Result of a complete TOTP setup operation
 */
export interface TOTPSetupResult {
    /** Base32-encoded secret for storage */
    secret: string;
    /** otpauth:// URI for manual entry */
    uri: string;
    /** QR code as data URL for scanning */
    qrCode: string;
}
/**
 * TOTPEngine - Time-based One-Time Password generation and validation
 *
 * Provides RFC 6238 compliant TOTP operations for two-factor authentication.
 * Uses the otpauth library for TOTP operations and qrcode for QR code generation.
 * Works in both browser and Node.js environments.
 *
 * Requirements:
 * - 2.1: Generate RFC 6238 compliant time-based one-time passwords
 * - 2.2: Validate TOTP codes with configurable time window tolerance
 * - 2.3: Generate base32-encoded secrets for TOTP setup
 * - 2.4: Generate otpauth:// URIs for authenticator app configuration
 * - 2.5: Generate QR codes as data URLs for authenticator app scanning
 * - 2.6: Support SHA1, SHA256, and SHA512 algorithms with configurable digit count and period
 *
 * @example
 * ```typescript
 * // Complete setup flow
 * const { secret, uri, qrCode } = await TOTPEngine.setup({
 *   issuer: 'BrightChain',
 *   label: 'user@example.com'
 * });
 *
 * // Generate a code
 * const code = TOTPEngine.generate(secret);
 *
 * // Validate a code
 * const isValid = TOTPEngine.validate(userInput, secret);
 * ```
 */
export declare class TOTPEngine {
    /**
     * Create a new random base32-encoded secret for TOTP setup.
     *
     * The secret is generated using cryptographically secure random bytes
     * and encoded in base32 format for compatibility with authenticator apps.
     *
     * **Validates: Requirement 2.3** - Generate base32-encoded secrets for TOTP setup
     *
     * @returns A base32-encoded secret string
     *
     * @example
     * ```typescript
     * const secret = TOTPEngine.createSecret();
     * // Returns something like "JBSWY3DPEHPK3PXP"
     * ```
     */
    static createSecret(): string;
    /**
     * Generate a TOTP code for the given secret.
     *
     * Generates an RFC 6238 compliant time-based one-time password using
     * the provided secret and optional timestamp.
     *
     * **Validates: Requirement 2.1** - Generate RFC 6238 compliant time-based one-time passwords
     *
     * @param secret - Base32-encoded secret
     * @param timestamp - Optional timestamp in milliseconds (defaults to current time)
     * @returns The generated TOTP code as a string
     *
     * @example
     * ```typescript
     * const code = TOTPEngine.generate(secret);
     * // Returns something like "123456"
     *
     * // Generate code for a specific time
     * const pastCode = TOTPEngine.generate(secret, Date.now() - 30000);
     * ```
     */
    static generate(secret: string, timestamp?: number): string;
    /**
     * Validate a TOTP code against the given secret.
     *
     * Validates the provided token against the secret with a configurable
     * time window tolerance to account for clock drift.
     *
     * **Validates: Requirement 2.2** - Validate TOTP codes with configurable time window tolerance
     *
     * @param token - The TOTP code to validate
     * @param secret - Base32-encoded secret
     * @param window - Number of periods to check before and after current time (default: 1)
     * @returns true if the token is valid within the time window, false otherwise
     *
     * @example
     * ```typescript
     * const isValid = TOTPEngine.validate('123456', secret);
     *
     * // With larger window for more tolerance
     * const isValidLargeWindow = TOTPEngine.validate('123456', secret, 2);
     * ```
     */
    static validate(token: string, secret: string, window?: number): boolean;
    /**
     * Generate an otpauth:// URI for authenticator app configuration.
     *
     * Creates a URI that can be used to configure authenticator apps
     * either manually or via QR code scanning.
     *
     * **Validates: Requirements 2.4, 2.6** - Generate otpauth:// URIs with configurable parameters
     *
     * @param secret - Base32-encoded secret
     * @param config - TOTP configuration options
     * @returns An otpauth:// URI string
     *
     * @example
     * ```typescript
     * const uri = TOTPEngine.generateOtpauthUri(secret, {
     *   issuer: 'BrightChain',
     *   label: 'user@example.com',
     *   algorithm: 'SHA256',
     *   digits: 6,
     *   period: 30
     * });
     * // Returns: "otpauth://totp/BrightChain:user@example.com?secret=...&issuer=BrightChain&algorithm=SHA256&digits=6&period=30"
     * ```
     */
    static generateOtpauthUri(secret: string, config: TOTPConfig): string;
    /**
     * Generate a QR code as a data URL from an otpauth:// URI.
     *
     * Creates a QR code image that can be scanned by authenticator apps.
     * The result is a data URL that can be used directly in an img src attribute.
     *
     * **Validates: Requirement 2.5** - Generate QR codes as data URLs for authenticator app scanning
     *
     * @param otpauthUri - The otpauth:// URI to encode
     * @returns A Promise resolving to a data URL string (e.g., "data:image/png;base64,...")
     *
     * @example
     * ```typescript
     * const uri = TOTPEngine.generateOtpauthUri(secret, config);
     * const qrCode = await TOTPEngine.generateQRCode(uri);
     * // Use in HTML: <img src={qrCode} />
     * ```
     */
    static generateQRCode(otpauthUri: string): Promise<string>;
    /**
     * Complete TOTP setup: create secret, generate URI and QR code.
     *
     * Convenience method that performs all setup steps in one call:
     * 1. Generates a new random secret
     * 2. Creates the otpauth:// URI
     * 3. Generates the QR code
     *
     * **Validates: Requirements 2.1, 2.3, 2.4, 2.5, 2.6** - Complete TOTP setup flow
     *
     * @param config - TOTP configuration options
     * @returns A Promise resolving to an object containing secret, URI, and QR code
     *
     * @example
     * ```typescript
     * const { secret, uri, qrCode } = await TOTPEngine.setup({
     *   issuer: 'BrightChain',
     *   label: 'user@example.com',
     *   algorithm: 'SHA256'
     * });
     *
     * // Store secret securely
     * // Display qrCode to user for scanning
     * // Optionally show uri for manual entry
     * ```
     */
    static setup(config: TOTPConfig): Promise<TOTPSetupResult>;
}
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