CryphoCat

Offline asymmetric encryption tool for private messaging. Supports RSA, ECC, Curve25519, and Kyber post-quantum algorithms. Single executable — double-click to launch native Windows GUI, or run in a terminal for interactive CLI mode.

中文说明

Highlights

• 10 cryptographic algorithms: RSA-2048/3072/4096, ECC P-256/P-384/P-521, Curve25519, Kyber-512/768/1024
• Compact output: Base64 + zlib compression reduces ciphertext length by ~60% compared to hex encoding
• Memory-first: keys default to in-memory storage, disk optional
• Image support: load an image and it will be auto-encoded to base64 before encryption; on decryption, images are detected and displayed in a preview window
• Clipboard integration: one-click copy of your public key; import a friend's key directly from the clipboard
• File hashing: built-in MD5 / SHA1 / SHA256 computation and verification
• Native Windows GUI, ~7.7 MB binary
• 10 interface languages: EN, 简体中文, 繁體中文(臺灣/香港), 日本語, 한국어, Русский, Français, Deutsch, Español
• Fully offline, no telemetry, no data leaves your machine

Quick Start

Download from Releases.

cryphocat.exe                    # auto-detect: terminal -> CLI, double-click -> GUI
cryphocat.exe --gui              # force GUI
cryphocat.exe --cli --lang zhcn  # force CLI, Chinese interface

Keys are stored in .cryphocat_keys/ by default, or in memory only when the checkbox is ticked.

Build

Requires Go 1.22+. Install rsrc once: go install github.com/akavel/rsrc@latest.

cd go-source
rsrc -manifest cryphocat.manifest -ico favicon.ico -o rsrc.syso
go build -ldflags="-s -w" -o cryphocat.exe .
go test ./...                     # run tests

Non-Windows builds (CLI only): skip rsrc, just run go build.

Development Plan

• RSA-OAEP, ECC (ECDH+AES-GCM), Curve25519, Kyber ML-KEM encryption
• File hash computation and verification (MD5/SHA1/SHA256)
• Auto-copy ciphertext to clipboard; import/export keys via clipboard
• 10-language i18n with automatic OS language detection on Windows
• Native Windows GUI (~7.7 MB, down from 42 MB)
• Auto-detect CLI vs GUI mode at startup
• Tag-triggered GitHub Release with auto-generated release notes
• Image loading for base64-encoding before encryption, with preview on decryption
• Base64+zlib compact output encoding
• In-memory key storage