Tessercube is a free iPhone app developed by SUJITEKU LIMITED LIABILITY CO. It falls under the category of Utilities & Tools and offers a range of basic functionalities for managing OpenPGP keypairs. Users can generate, import, and export keypairs, with support for EdDSA keys. The app also allows for the encryption and decryption of messages, as well as the signing and verification of signed messages.

One of the special features of Tessercube is its Tessercube Keyboard, which enables users to communicate via OpenPGP in any app. This feature is particularly useful when all participants of a conversation have installed Tessercube or any other software supporting OpenPGP implementations.

Tessercube also provides a unified message history log, allowing users to easily keep track of their encrypted communications.

Overall, Tessercube offers a secure and convenient solution for OpenPGP key management and communication on the iPhone.