export declare const COMPRESSED_PUBLIC_KEY_HEX_LENGTH = 66;
/**
 * Converts a public key hex string to x-only format (32 bytes, no prefix).
 * Validates the input format and rejects unexpected key types.
 *
 * @param publicKeyHex - Hex-encoded public key (compressed 66-char or x-only 64-char)
 * @returns 64-character hex string representing the x-only public key
 * @throws WalletError if the key format is invalid
 */
export declare function toXOnlyPublicKeyHex(publicKeyHex: string): string;
