/**
 * Converts a DER-encoded ECDSA signature to a fixed 64-byte length format.
 *
 * @param derSignature - The DER-encoded ECDSA signature (Uint8Array).
 * @returns A 64-byte fixed-length signature (Uint8Array).
 */
export declare const convertDerToFixed64: (derSignature: Uint8Array) => Uint8Array;