/**
 * derive secret key from password user typed-in
 * use sha256x2 as key derivation function(kdf)
 * @param  password user's password in utf8
 * @param  salt     default salt in hex
 * @return secretKey string in hex (16 bytes because of sha256)
 */
export declare function derive(password: string, salt: string): string;
/**
 * verify secret key from password and salt
 * @param  password  old password in utf8
 * @param  salt      default salt in hex
 * @param  secretKey secret key in hex
 * @return boolean of verify success or not
 */
export declare function verify(password: string, salt: string, secretKey: string): Boolean;