Cryptalk

Role / Services

  • Backend development

Context

  • Messaging backend

Location & year

  • Hungary ©

Cryptalk title card: end-to-end encrypted messaging backend

Overview

Messages the server cannot read.

Cryptalk is the backend for a future mobile messaging app focused on end-to-end encryption, privacy and data minimization. Message content is never exposed to the server and never stored in readable form.

The project is currently a layered backend without a frontend. A Blazor MAUI mobile client is planned, and the API is designed to support it without a redesign.

Architecture

  • Domain

    Core entities and rules for secure messaging, encryption workflows and sessions, isolated from infrastructure concerns.

  • Application

    Use cases such as message creation, encryption pipelines and session handling.

  • Infrastructure

    Persistence and cryptographic implementations. SQL Server stores messages only as encrypted payloads.

  • API

    Frontend-agnostic endpoints for authentication, request validation and encrypted payload transmission.

Security model

A zero-knowledge relay.

Encryption and decryption happen only on the devices. The backend is a transport and coordination layer, so even with database access the stored messages remain unreadable.

Cryptographic operations sit behind dedicated service boundaries in the infrastructure layer, separate from business logic, and the data model supports session-based retrieval of encrypted payloads.

Technologies

  • ASP.NET Core
  • C#
  • Clean Architecture
  • SQL Server
  • End-to-end encryption