/** Concatenate multiple Uint8Arrays into one. */
export declare function concat(...arrays: Uint8Array[]): Uint8Array;
/** Constant-time comparison of two byte arrays. */
export declare function constantTimeEqual(a: Uint8Array, b: Uint8Array): boolean;
/** Decode base64 string to bytes, or pass through Uint8Array unchanged. */
export declare function decodeBase64Bytes(input: Uint8Array | string): Uint8Array;
/** Convert a UTF-8 string to bytes, or pass through Uint8Array unchanged. */
export declare function toBytes(input: Uint8Array | string): Uint8Array;
/** Import a PEM-encoded SPKI public key as a CryptoKey for ECDSA P-256 verification. */
export declare function importPemPublicKey(pem: string): Promise<CryptoKey>;
/** Export a CryptoKey to PEM-encoded SPKI format. */
export declare function exportKeyToPem(key: CryptoKey): Promise<string>;