Phasm: Steganography

Christoph Gaffga

About this app

Hidden in plain sight.

Phasm hides your messages — and files — inside ordinary photos using steganography. The photo looks identical to the human eye, but it carries encrypted data that only the intended recipient can extract with the right passphrase. Hide secret messages in photos that no one knows are there.

TWO MODES FOR TWO NEEDS

• Ghost Mode — Maximum stealth. Uses advanced adaptive steganographic algorithms (J-UNIWARD + syndrome-trellis coding) to make hidden data virtually undetectable, even by statistical steganalysis tools. Supports file embedding: attach documents, images, or archives alongside your hidden text message. When you use a non-JPEG photo, Deep Cover mode activates automatically for even greater capacity.

• Armor Mode — Maximum durability. Your hidden message survives JPEG recompression, cross-library re-encoding, and mild cropping. Fortress sub-mode auto-activates for short messages and survives aggressive compression from popular messaging apps.

SERIOUS ENCRYPTION

• AES-256-GCM-SIV authenticated encryption on every message — always on, not optional.
• Argon2id key derivation — resistant to brute-force and GPU attacks.
• ChaCha20-based deterministic randomness for embedding.
• Post-quantum safe — 256-bit symmetric encryption remains secure against quantum computers.
• No backdoors. No key escrow. You hold the only key.

PRIVACY BY DESIGN

• All encoding and decoding happens on your device. Nothing is uploaded.
• No account required. No sign-up. No tracking. No ads.
• Open-source Rust cryptographic engine — auditable by anyone.
• Designed for journalists, researchers, activists, curious tinkerers — or just for fun.

SHARE YOUR WAY

• Share stego photos via email, direct messaging, or any app that handles images.
• phasm.link — generate a short link so recipients can decode without installing anything, right in the browser.
• Available on mobile and web — your recipients can decode on any platform.
• For guaranteed delivery through messaging apps, use “send as file” to prevent recompression.

BUILT FOR ANDROID

• Material You dynamic color — the app adapts to your device’s color theme.
• App Shortcuts — long-press the icon to jump straight to Encode or Decode.
• Tablet-optimized layouts with navigation rail and two-column design.
• Per-App Language Picker — choose a different language just for Phasm.
• Supports JPEG, PNG, GIF, WebP, and progressive JPEG input — auto-converted for embedding.
• Real-time decode progress with integrity scoring.
• Brotli-compressed payloads for maximum capacity.
• 37 languages supported.

HONEST ABOUT LIMITATIONS

• Social media platforms that resize or re-encode photos may destroy hidden data. Use direct sharing or “send as file” for reliable delivery.
• Message capacity depends on image resolution — larger photos carry more data.
• Steganography hides the existence of a message. Encryption protects its content. Phasm gives you both.

What’s new

Hide encrypted messages in photos — invisible to the eye, undetectable by analysis. Two modes: Ghost (stealth) and Armor (survives recompression). AES-256 encryption, shadow messages for plausible deniability, cloud sharing via links.