People, organizations, devices need to make many kinds of claims as part of their everyday activities. Digital credentials can enable to transmit instantly verifiable claims about their name, date of birth, gender, location, accomplishments. Some privacy-enhancing digital credentials enable revealing only part of your identity and thus hiding all information that is not necessarily needed for the online service. In the past two decades, several privacy- and trust-enhancing authentication techniques and approaches have been proposed to implement such verifiable digital credentials, mostly on the theoretical level. Some implementations exist, but either lack functionalities, rely on heavy computational machinery or are not available in open source. This paper presents emmy, a fully-fledged open source cryptographic library for secure, privacy-aware, and trust-enhancing authentication towards online services.