Zk-nyms
Anonymous credentials that use zero-knowledge proofs so users can access digital apps and services without having to reveal sensitive information.
What do zk-nyms do?
Accessing or paying for services online often requires us to reveal sensitive information about ourselves, and more than should be necessary. With zk-nym credentials, it is possible to anonymously prove your right to access digital services while retaining your privacy. Zk-nyms are the basis of NymVPN's anonymous credential system in which user payments can never be linked to their usage of the network. Zk-nyms can also be integrated to any service, such as e-cash, to delink clients' personal data from their authorized access.
zk-nym use cases
mixnet credential
Use and pay for the mixnet in a privacy preserving manner, ensuring wallet address and transaction history cannot be linked to your mixnet usage.
e-cash payments
Protect your privacy while paying online. The zk-nym scheme can be used for e-cash to ensure private financial transactions, also when paying via cryptocurrencies and utility tokens like NYM.
Data sovereignty
Prove attributes of your identity while retaining privacy. For example, prove you are above a certain age without revealing your actual birth date.
Private authentication
Sign in to digital services in a privacy preserving manner, ensuring that your information is delinked so you are not traced across apps, sites, and services.
Getting zk-nyms
Issuance
You can request anonymous credentials from what are called “issuing authorities.” For the mixnet, the issuing authorities are the Nyx blockchain validators.
Validation
The validators issue anonymous credentials that have “threshold issuance": they only hold part of the key of the credential and cannot piece together the full key to de-anonymize you.
Use
You now have an anonymous credential that you can use to cryptographically prove something about yourself to a “verifier" or the given digital service you are trying to use.
Privacy properties of zk-nyms
Threshold issuance
Validators only hold a part of the key that signs the credential. This has a similar byzantine-fault tolerance as other validator bases schemes: not only does it distribute trust but it also avoids “crush” of the system in case some validators go offline or are malicious.
Blind signatures
The property of blind issuance means that even if all the validators colluded, they would not be able to piece together the private attribute of your credential.
Unlinkability
Once you have your credential, rest assured that the issuance of your credential and your subsequent showing of it is unlikable. Even if validators collude with the service to which you show your credential, they cannot learn any additional information.
Re-randomizable signatures
Signatures are re-randomizable, meaning you can use the credentials again without making these traceable and compromising privacy.
Build with zk-nym credentials
zk-nym credentials are available as an open source library with Nyx blockchain validators as issuing authorities. The library makes zk-nyms available to everyone, with no work required by the end-user. Built on the Coconut credentials protocol, the first use-case is anonymous access credentials for the Nym mixnet.
Read more
zk-nyms are here — a major milestone towards a market-ready mixnet
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Frequently Asked Questions
How do zk-nyms keep my NymVPN subscription private?
How do zk-nyms keep my NymVPN subscription private?
When you pay for a NymVPN subscription, your payment is converted to NYM tokens which are then used to issue you an anonymous zk-nym credential which your NymVPN app will use to access the network. While Nym Technologies will have access to your payment information, no one, not even Nym Technologies, will be able to connect this information to your access or use of the network. Your identity remains unlinkable to what you do online with NymVPN.
Can I use zk-nyms to anonymize my payments online?
Can I use zk-nyms to anonymize my payments online?
Currently zk-nyms are only being used to serve as proof of payment for the NymVPN app. However, zk-nyms can be integrated with generic e-cash payment systems to make transactions private and protect against cyber attacks to wallets. Nym is currently completing an integration for Z-Cash, but only using our the Nym Noise Generating Mixnet (NGM). Nym recommends Z-Cash currently for anonymous payments.
Can zk-nyms protect my crypto transactions?
Can zk-nyms protect my crypto transactions?
Currently, zk-nyms are only being used to serve as proof of payment for the NymVPN app using cryptocurrency. However, zk-nyms are built to defend any application, including cryptocurrencies and wallets. Wallet integrations in the future could use zk-nym technology as offline e-cash to enable better protection for cryptocurrencies like Bitcoin. Stay tuned!