NSData *hmac = [self hmac: encrypted withKey: hmacKey withIV: iv withA:
[baseHeader dataUsingEncoding:NSASCIIStringEncoding]];

return [NSString stringWithFormat:@"%@.%@.%@.%@.%@", baseHeader, baseCEK, baseIV, basePayload, [[self hmacToTag: hmac] unpaddedBase64URLEncoded]];