PostGuard is a free platform for securely sending emails and files. These are two separate services. They both offer confidentiality: protection against reading by the wrong person(s). PostGuard encrypts your emails and files in such a way that only the recipient that you choose can decrypt, and then read them. This works via the free Yivi app for attribute-based authentication: you, as sender choose certain personal attributes of the intended receiver (such as email address, phone number or name). The receiver must then prove, via the Yivi app, to be in possession of these attributes, before the mail/file can be decrypted and read. This is the essence of PostGuard: it reduces confidentiality to authentication. PostGuard is offered for free, as a social service, to make encrypted mail and file sharing easy for everyone. PostGuard was originally developed by the iHub team at Radboud University (RU), with support from NWO and SIDN fonds.

PostGuard is now operated by Yivi in the Netherlands. As explained in more detail below, Yivi is the data controller, in the sense of Europe's General Data Protection Regulation (GDPR): it determines the purposes and means. Yivi is also a PostGuard data processor. For PostGuard file sharing Yivi is a data processor jointly with the company ProcoliX. Only data that is necessary for the PostGuard service is processed.

Both email and file encryption make use of Identity-Based-Encryption (IBE) via a Key Generation Service (KGS) that is run by Yivi. A receiver of an email or file can obtain a decryption key from the KGS after proper authentication (via Yivi). The disclosed attributes are processed very briefly by Yivi in order to check if they match the requirements, so that a decryption key can be generated. Immediately after key generation, or after a failed disclosure, the relevant attributes (and associated timestamped IP-addresses) are deleted. Yivi does not maintain a log of these data in such disclosures. Yivi does count the number of disclosures and the rough location (at country level) of their origin. These data are used only for usage statistics and service improvements.

• When you use PostGuard to send encrypted emails, these emails are encrypted on your own device and follow their usual routes via your own email provider. They do not pass through Yivi, either as plaintext or encrypted. Hence Yivi does not process your emails. The only exception is when an email is too large to send directly by email: in that case the encrypted email is uploaded to the file-sharing server (hosted by ProcoliX), just like the file transfer described below. If you use the PostGuard browser-based decryption service for decrypting your emails, the actual decryption takes place in your own web browser. Hence, also in this case, Yivi does not process your emails.
• Transferring files via PostGuard happens via a website hosted by ProcoliX. Via this website, only the email addresses of the sender and the recipient are processed. These are needed to send notifications about the transfer, both to the recipient and to you as a confirmation. The receiver's email address is also used as a (standard) attribute to enable encryption and decryption via PostGuard. Only the email address is mandatory: as the sender, you may optionally require the recipient to prove extra attributes (such as their name, phone number, or date of birth), and you may optionally sign the transfer with your own verified attributes (such as your name, phone number, or date of birth). These extras are never required. Sent emails and email addresses are not stored longer than strictly necessary, that is, at most 2 weeks. When you use PostGuard to transfer files, the encrypted files will be stored temporarily at ProcoliX. ProcoliX cannot see the contents of these files because they are encrypted. Each file is accompanied by some basic metadata, like the type of attribute used for encryption and a timestamp. The attribute values are purged. The encrypted files plus these metadata are kept for a maximum of 2 weeks and are then automatically deleted. Other technical personal data, such as IP addresses, are stored and deleted according to ProcoliX's general policy. When everything is running normally, this data is deleted after two days. ProcoliX temporarily stores the encrypted files but does not have access to the cryptographic keys (private keys) required for decryption. Yivi generates the private keys but does not have access to the encrypted files. ProcoliX and Yivi do not conspire to jointly decrypt files behind the backs of users.

Technical changes to the PostGuard system, or any new services, may result in modification of this privacy policy. Yivi and ProcoliX reserve the right to make such changes and will announce the new privacy policy as soon as possible via this page. For any questions, comments, or complaints about this processing by Yivi and/or ProcoliX for PostGuard, please contact the PostGuard team at our contact address. For complaints about the processing of data by Yivi or ProcoliX, the Dutch Authority for the Protection of Personal Data (Autoriteit Persoonsgegevens) can also be contacted.