/**
 * PDF encryption support (Standard Security Handler, V=5, R=5).
 *
 * Implements AES-256 encryption compatible with PDF 2.0 (ISO 32000-2:2020).
 * Supports:
 * - User password (required to open the document)
 * - Owner password (grants full access)
 * - Permission flags (print, copy, modify, etc.)
 *
 * The file encryption key (FEK) is a random 256-bit key.
 * All streams and strings are encrypted using AES-256-CBC with a random
 * 16-byte IV prepended to each encrypted value.
 *
 * @see ISO 32000-2:2020, §7.6 — Encryption
 */
/**
 * PDF encryption options.
 */
export interface PdfEncryptionOptions {
    /** User password (required to open the document). Empty string = no open password. */
    userPassword?: string;
    /** Owner password (grants full permissions). Required. */
    ownerPassword: string;
    /** Permissions to grant when opened with user password. */
    permissions?: Partial<PdfPermissions>;
}
/**
 * PDF document permissions (what a user-password holder can do).
 * All default to false.
 */
export interface PdfPermissions {
    /** Allow printing */
    print: boolean;
    /** Allow modifying content */
    modify: boolean;
    /** Allow copying text/images */
    copy: boolean;
    /** Allow adding/modifying annotations */
    annotate: boolean;
    /** Allow filling form fields */
    fillForms: boolean;
    /** Allow extracting content for accessibility */
    accessibility: boolean;
    /** Allow assembling (insert/rotate/delete pages) */
    assemble: boolean;
    /** Allow high-quality printing */
    printHighQuality: boolean;
}
/**
 * Encryption state used during PDF generation (V=5, R=5, AES-256).
 */
export interface EncryptionState {
    /** 32-byte file encryption key */
    encryptionKey: Uint8Array;
    /** 48-byte O value: hash(32) + validation salt(8) + key salt(8) */
    oValue: Uint8Array;
    /** 48-byte U value: hash(32) + validation salt(8) + key salt(8) */
    uValue: Uint8Array;
    /** 32-byte encrypted owner key (OE) */
    oeValue: Uint8Array;
    /** 32-byte encrypted user key (UE) */
    ueValue: Uint8Array;
    /** 16-byte encrypted permissions (Perms) */
    permsValue: Uint8Array;
    /** Permissions integer (P value) */
    permissions: number;
    /** File identifier (16 bytes) */
    fileId: Uint8Array;
}
/**
 * Initialize encryption state for AES-256 (V=5, R=5).
 */
export declare function initEncryption(options: PdfEncryptionOptions): EncryptionState;
/**
 * Encrypt data for a PDF object using AES-256-CBC.
 *
 * For V=5/R=5, the file encryption key is used directly (no per-object key derivation).
 * A random 16-byte IV is prepended to the ciphertext.
 */
export declare function encryptData(data: Uint8Array, _objectNumber: number, _generation: number, encryptionKey: Uint8Array): Uint8Array;