Show HN: CardGo – Reusable, end-to-end encrypted context cards for AI chats

CardGo, a new Chrome extension from an independent developer, lets users create reusable, end-to-end encrypted context cards to attach to AI chats including ChatGPT, Claude, Gemini, Perplexity, and Grok. Cards are encrypted with AES-256-GCM, keys are generated on the user's device and never sent to CardGo, and the company stores only ciphertext. The extension is available now, with a desktop app and mobile keyboard planned.

Work Product design lead · Remote Prefers concise briefs Timezone: Tokyo GMT+9 Save your context once. The CardGo Chrome extension brings it to any AI chat — ChatGPT, Claude, Gemini, Perplexity, Grok, and more. Your cards, at a glance Encrypted at rest · Nothing shared until you attachProduct design lead · Remote Prefers concise briefs Timezone: Tokyo GMT+9 Training for a half marathon Vegetarian Knee-friendly plans only Planning life with two little ones Weekend ideas Budget-conscious picks Encrypted at rest · Nothing shared until you attach Works with How to use CardGo Install the Chrome extension, create a card, and attach it when you chat with AI. Add CardGo to Chrome. Your cards will be ready beside the AI chats you use. Save the context you want to reuse, from your role and goals to your preferences. Choose the card you need in ChatGPT, Claude, Gemini, Perplexity, Grok, or another supported AI. Coming soon A dedicated desktop app for your cards and context. A mobile keyboard for Android and iOS that brings your cards into any app. Pick an everyday scenario and watch the same question answered twice—once without your card, once with it. Your card — a few lines about you Your question A recorded example. Nothing leaves your browser—pick a scenario and watch the same question answered twice. How it works Profile, Now, Goals, Guidance, Memory, Timeline, Skills. Fill in what’s useful, skip the rest—empty sections save nothing. Pick one below to see what goes in it. What is this card about? Who or what this card is about. The things you would say first if someone asked, and would still be true next quarter. Stable — changes in months, not days Profile New in CardGo Keeping a profile current is work, and work is why profiles go stale. So CardGo drafts the cards, surfaces the right one as you type, and files what you say back where it belongs. Live now One paragraph in — a named set out, already sorted into sections. You keep the ones that are right. I lead product design at a startup in Tokyo, I’m training for a half marathon, and I have two kids under five. Suggestions and Capture read only your own draft, and read it on your device — a small model in your browser, not a server. CardGo never reads the conversation, and nothing is attached, saved, or changed until you tap. Why CardGo Choose what each chat knows Attach only the card a conversation needs. Nothing else is shared. Switch AIs without starting over One card works in ChatGPT, Claude, Gemini, Perplexity, and Grok. Encrypted end-to-end Cards are locked on your device with a key we never receive. We store ciphertext. Filter sensitive details before sharing Review the snapshot before you attach a card. Sensitive values are filtered on your device, so you can see exactly what the AI will receive. Share one card—not your profile Send a read-only card when it helps. You decide exactly what goes with it. Your cards are sealed on your device with a key we never receive. What reaches CardGo is ciphertext — we can sync it, count it, and delete it, but we cannot read it. What you write Work Product design lead · Timezone: Tokyo GMT+9 What our servers store An opaque block of ciphertext.Ciphertext · 412 bytes · rev 7 — and nothing else Your key is born on your device The vault key is generated in your browser and never sent to CardGo. No copy, no escrow, no reset. AES-256-GCM, a key per card Every card gets its own content key, sealed with the platform’s audited crypto before it is uploaded. Our servers hold ciphertext We sync opaque blobs, sizes, and timestamps. Nobody at CardGo can read a card — there is no key to read it with. A recovery phrase only you hold Setup shows a 15-word phrase once and asks you to confirm it. We never store it, so only you can restore a vault. Encryption protects your cards from us — it cannot protect what you deliberately send to an AI provider. Once you attach a card, that context is governed by that provider’s terms. Read the full privacy policy /privacy . Early access Install the extension, build your first context card, and bring it to your next AI conversation. Free early access · No credit card