export declare let APPROVED_EXTENSION_HEADERS: string[];
export type ApprovedExtensionHeader = typeof APPROVED_EXTENSION_HEADERS[number];
export type X402Extension = {
    header: ApprovedExtensionHeader | string;
    payload: Record<string, any>;
    [k: string]: any;
};
export declare function canonicalizeExtensionHeader(h: string): string;
export declare const isApprovedExtensionHeader: (h: string) => boolean;
export declare function registerApprovedExtensionHeader(header: string): void;
export type X402SecurityPayload = {
    jwksUrl?: string;
    jwks?: any;
    minKeyStrength?: number;
    allowedSuites?: string[];
};