export declare function writeHeader(formatEnum: number, framed: boolean, nonce: Uint8Array, chunkSize: number): Uint8Array;
export declare function readHeader(header: Uint8Array): {
    formatEnum: number;
    framed: boolean;
    nonce: Uint8Array;
    chunkSize: number;
};
/** 12-byte counter nonce: 11-byte BE counter + 1-byte final flag. */
export declare function makeCounterNonce(counter: number, finalFlag: number): Uint8Array;