/**
 * Given a key and message, generate a fernet token.
 *
 * @param crypto The web-crypto api.  Either window.crypto or require("node-webcrypto-ossl").
 * @param secret A base64 encoded fernet key (https://github.com/fernet/spec/blob/master/Spec.md#key-format)
 * @param now The current timestamp encoded as an ISO8601 time string
 * @param iv The IV to use, represented as a 16 byte Uint8Array
 * @param src The string to encode
 */
export declare function generate(crypto: Crypto, secret: string, now: string, iv: Uint8Array, src: string): Promise<string>;
/**
 * Given a key and token, verify that the token is valid and recover the original message.
 *
 * @param crypto The web-crypto api.  Either window.crypto or require("node-webcrypto-ossl").
 * @param secret A base64 encoded fernet key (https://github.com/fernet/spec/blob/master/Spec.md#key-format)
 * @param encodedToken A fernet token
 * @param ttl The time-to-live; if set, the token must be less than ttl seconds old otherwise it won't be decoded
 */
export declare function verify(crypto: Crypto, secret: string, encodedToken: string, ttl?: number): Promise<string>;