BlockChat
Decentralized Mobile Messenger App
BlockChat allows users to establish secure, intentional connections via phone numbers, email, or QR codes, enabling conversations only with selected contacts. User conversations are not stored, ensuring strong data ownership and privacy.
I led the end-to-end product experience across connection flows, secure messaging, and privacy focused voice interactions, collaborating closely with the CTO, engineering team, and business marketing teams.
For several months after launch, I worked directly with customer support to translate real user feedback improvements, ensuring that privacy principles remained usable in real world contexts. Blockchat launched successfully.
Company
GlobalFinance Inc.
Services
Visual Design
UI & UX Design
Industries
Travel
Role
January 2025
My entry into the project
& Challenge
In South Korea, a fire at KakaoTalk’s data center caused a nationwide service outage, making the country’s dominant messaging app inaccessible for millions of users. The incident exposed a critical reality: personal conversations and essential digital communication were entirely dependent on centralized infrastructure.
Within days, over 2 million users left KakaoTalk, migrating to alternative platforms such as Telegram and LINE. The event triggered public backlash and raised broader concerns around reliability, privacy, and systemic risk in centralized messaging services. This incident highlighted a fundamental mismatch between user expectations and existing system architectures.
+EMPLOYEES SPYING ON CELEBRITIES
Personal conversations are treated as centralized data assets rather than private exchanges.
A single point of failure can disrupt communication at a national scale.
Users lack meaningful control over how and where their conversations are stored.
The outage reframed digital messaging as an infrastructure problem, not just a product issue revealing the need for communication systems that prioritize user control, privacy, and resilience by design.
My Role - Lead UX/UI Designer
As the Lead UX/UI Designer for the BlockChat mobile app, I designed and launched BlockChat’s features: 'Intentional Connections', 'Secure Messaging' and 'Voice Calling with Privacy Controls' from an idea written on an A4 sheet of paper. As the lead designer working alongside a Tech Lead (CTO), 4 engineers, and 2 designers, I managed both development planning and design across the mobile app, website, and brand.
Process
From Idea to Direction: Iterating with Leadership and Engineering
Blockchat was designed through an iterative, Agile-based process with continuous collaboration across design, engineering, and leadership teams. Every 1–2 weeks, I led design reviews using wireframes and prototypes to evaluate ongoing UX and UI decisions with the leadership team. Necessary and unnecessary ideas were deliberately filtered, refined, and prioritized, and feedback from each session directly informed the next design iteration. This cycle continued before and after development, ensuring alignment throughout the entire product lifecycle.
Building the Foundation: Defining Structure Before Visuals
Once the information architecture, core user flows, and technology boundaries were clearly defined, we established a functional design skeleton. Based on this foundation, I led the application of product branding—defining the color system, typography, and visual language—while continuously refining the UX in parallel. Backend engineers began development based on this structural foundation, followed by frontend engineers joining after the brand system and high-fidelity designs were finalized, enabling efficient and high-quality implementation.
Extending Design Beyond the Product: Supporting Launch and Growth
Beyond product design, I collaborated closely with design and business teams to support PR and go-to-market strategy. I contributed to market analysis, competitive research, and user experience insights, translating deep product knowledge into strategic inputs for marketing. This collaboration extended to executing a nationwide television advertising campaign in partnership with an external agency.
Product Principles & Constraints
Privacy by Default
User conversations were designed to remain private by default. Messages were not stored centrally, reducing exposure to data retention risks, legal requests, and infrastructure failures. Design decisions around connection approval, message control, and data handling were aligned with this principle.
User Controlled Connections
The product prioritized explicit user consent over automated behaviors. Features such as automatic contact syncing and inferred social graphs were intentionally excluded. Users define who they connect with and how conversations are managed, increasing transparency and trust.
Clear and Predictable System Behavior
Interfaces were designed to clearly communicate connection states, permissions, and messaging outcomes. This reduced user confusion and minimized the need for onboarding or additional guidance.
Design Within Technical Constraints
The product was designed within constraints related to decentralized identity, blockchain-based verification, and security requirements. These constraints informed simplified user flows, limited feature scope, and reduced system complexity.
Scalability Through Focused Scope
Feature decisions favored a limited set of core use cases over broad feature coverage. This approach supported system stability, maintainability, and long-term scalability.
Key Trade offs & Decisions
Designing Blockchat required balancing privacy, usability, and scalability. Product decisions prioritized long term trust and system reliability over short-term convenience.
1. Automatic Contact Sync VS. Intentional Connections
Shifted From: Automatic address book syncing for faster onboarding
Toward: Explicit, user approved connections
Automatic address book syncing was considered to reduce onboarding friction. This approach was rejected due to privacy risks and lack of explicit user consent. Instead, users create connections through phone numbers, email, or QR codes. Each connection requires explicit approval, ensuring conversations occur only with selected contacts. This decision increased onboarding effort and required alignment with leadership on growth expectations, but established trust and intentional use before scale.
2. Message Persistence VS. Data Ephemerality
Shifted From:: Server-side message storage for convenience and recovery
Toward: No conversation storage by default
Server side message storage was evaluated for synchronization and recovery benefits. This option was rejected because it conflicted with privacy and data ownership principles. The product does not store conversations by default. This reduced centralized data risk and exposure to data retention issues. The trade off introduced limited recovery options, but avoided architectural dependencies that would be difficult to change at scale.
3. Feature Breadth VS. Interaction Clarity
Shifted From: A wide set of messaging features common in mainstream apps
Toward: Focused, high control interaction tools
Rather than replicating feature heavy chat platforms, the product prioritized focused, high control interaction tools. This meant defining clear interaction boundaries including per connection controls and message level authority. Narrowing feature breadth required restraint, but resulted in a system that was easier to reason about and trust.
4. Speed of Adoption VS. Trustworthiness
Shifted From: Growth driven shortcuts to accelerate adoption
Toward: Measured rollout aligned with privacy guarantees
Some decisions slowed early adoption and increased internal debate across product and business teams. Trust was treated as a non negotiable requirement, with the belief that credibility lost early is rarely recoverable at scale. Also no advertisement in the chat room.
Features
Intentional Connections
“Intentional Connections” enables users to choose multiple methods of connecting with contacts, rather than relying on automatic contact imports based on device phone numbers. In designing the Intentional Connections feature, I defined the blockchain ID creation (sign-in) flow, a floating navigation control for initiating 1:1 and group connections, and a streamlined connection acceptance flow allowing users to interact seamlessly within the app without requiring additional guidance.
Secure Messaging
“Secure Messaging” empowers users to define each connection according to their own privacy preferences for each contact for in-app conversations. I designed “ Connection Codename Setting,” “Delete or Edit Messages,” “Switch Text Alignment,” “Change Text Colors,” and “Adjust Text Size” to enhance user authority over their conversations.
Voice Calling with Privacy Controls
‘Voice Calling with Privacy Controls’ allowed users to speak in real time without relying on a centralized server. I designed an AI Voice Filter that anonymizes vocal signatures in real time, giving users control over how their voice is used and ensuring it can’t be extracted, cloned, or submitted as legal evidence.
Impact
Reached 23,000+ downloads within the first few 3 months of launch.
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Ranked in the top 10 social categories in blockchain-based apps in the early adoption phase.
Achieved a 4.8/5 rating on Google Play, with user reviews citing “trustworthy,” “lightweight,” and “finally private.”
Enabled secure communication for cross border activist communities, where privacy is non negotiable.
Reflection
How It Shaped My UX Philosophy
I learned how to communicate design intent clearly through structured artifacts, including PRDs, design specs, and shared documentation, allowing stakeholders to align early and make informed decisions. Navigating trade offs and aligning UX direction with business goals sharpened my ability to design not just screens, but outcomes.
What I'm Most Proud Of
I was the first and only designer at the beginning, and as the team scaled to include 2 designers and 5 developers, I helped lead the product from inception to launch. I established our design system from scratch, enabling faster collaboration, scalable workflows, and consistent quality across the product. Watching the system I built empower others was just as rewarding as shipping the product itself.