A class which accepts an array of keys that are used to sign and verify data and allows easy key rotation without invalidation of previously signed data.

Given data and a digest, return the current index of the key in the keys passed the constructor that was used to generate the digest. If no key can be found, the method returns -1.

Take data and return a SHA256 HMAC digest that uses the current 0 index of the keys passed to the constructor. This digest is in the form of a URL safe base64 encoded string.

Given data and a digest, verify that one of the keys provided the constructor was used to generate the digest. Returns true if one of the keys was used, otherwise false.