/**
 * KDF Utility Functions
 *
 * Encoding, decoding, and cryptographic utilities for KDF operations.
 * Issue #1649
 */
/**
 * Convert a base64 string to Uint8Array
 */
export declare function base64ToUint8Array(base64: string): Uint8Array;
/**
 * Convert Uint8Array to base64 string
 */
export declare function uint8ArrayToBase64(bytes: Uint8Array): string;
/**
 * XOR two byte arrays of equal length
 *
 * Used for combining password-derived key with LocalSecret in 2SKD.
 * This follows the 1Password approach of XOR combination.
 *
 * @param a - First byte array
 * @param b - Second byte array
 * @returns XOR result
 * @throws Error if arrays are not the same length
 */
export declare function xorBytes(a: Uint8Array, b: Uint8Array): Uint8Array;
/**
 * Normalize password for key derivation
 *
 * Applies NFKD normalization and trims whitespace.
 * This ensures consistent key derivation across platforms.
 *
 * @param password - Raw password input
 * @returns Normalized password string
 */
export declare function normalizePassword(password: string): string;
/**
 * Generate cryptographically secure random bytes
 *
 * @param length - Number of bytes to generate
 * @returns Random bytes
 */
export declare function generateRandomBytes(length: number): Uint8Array;
/**
 * Generate a random salt for key derivation
 *
 * @returns 16-byte random salt as base64 string
 */
export declare function generateSalt(): string;
/**
 * Constant-time comparison of two byte arrays
 *
 * Prevents timing attacks when comparing secrets.
 *
 * @param a - First byte array
 * @param b - Second byte array
 * @returns true if arrays are equal
 */
export declare function constantTimeEqual(a: Uint8Array, b: Uint8Array): boolean;