/**
 * Byte/string codecs shared across the auth core — JWT (auth.ts), CSRF,
 * WebAuthn, TOTP, Web Push. One canonical copy: this encoding logic is
 * security-relevant (it feeds signatures and key material), and before this
 * module it existed 3-5× in parallel with the dependency arrows pointing the
 * wrong way (CSRF and the passkey stack imported base64url from the Web-Push
 * module). Everything here is Web-API-only (no `Buffer`).
 */
/** Bytes → unpadded base64url. */
export declare function base64UrlEncode(data: Uint8Array): string;
/**
 * base64url → bytes. Tolerant on input (read side): missing padding is
 * restored and the standard alphabet (`+/`) is accepted alongside `-_`.
 * Throws on undecodable input.
 */
export declare function base64UrlDecode(str: string): Uint8Array;
/** UTF-8 string → unpadded base64url — the JWT-segment form. */
export declare function base64UrlEncodeString(text: string): string;
/** base64url → UTF-8 string — the JWT-segment form. */
export declare function base64UrlDecodeString(str: string): string;
/** Concatenate byte arrays into one. */
export declare function concatBytes(...arrays: Uint8Array[]): Uint8Array;
/**
 * Coerce a Uint8Array (possibly a subarray view) to a plain ArrayBuffer for
 * the Web Crypto API, whose lib types reject the generic
 * `Uint8Array<ArrayBufferLike>`. Slices by byteOffset/byteLength so views
 * yield exactly their own bytes, never the whole backing buffer.
 */
export declare function toArrayBuffer(data: Uint8Array): ArrayBuffer;