Comparison

Underlayer vs Phasm

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Underlayer

Features
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UNDERLAYER - STEGANOGRAPHY MADE SIMPLE Transform ordinary images into secret carriers. Hide confidential messages invisibly within photos and share them through any messenger without raising suspicion. KEY FEATURES: HIDE SECRETS • Embed text messages invisibly into any image • Two encoding modes: Hidden (invisible pixels) and Open (colored frame) • Open mode survives messenger compression (Telegram, WhatsApp, etc.) • Share processed images directly or save to gallery REVEAL MESSAGES • Extract hidden text from steganographic images • Automatic detection of encoding method • Works with images received through messengers • Share intent support - open images directly from gallery WHY UNDERLAYER? • Simple & Intuitive - No cryptography knowledge required • Messenger-Friendly - Open mode designed for compressed sharing • Privacy First - All processing happens locally on your device • Universal - Works with JPG, PNG, WebP formats • No Account Required - Start using immediately USE CASES • Private communication through public channels • Watermarking images with hidden ownership data • Secure note-taking in plain sight • Educational tool for learning steganography • Fun way to send secret messages to friends SECURITY & PRIVACY • No internet connection required for processing • Your messages never leave your device • No data collection or tracking • Complete control over your secrets PREMIUM FEATURES • No banner ads at the bottom • No interstitial ad interruptions • Process unlimited images without ad breaks HOW IT WORKS 1. Select any image from your gallery 2. Enter your secret message 3. Choose encoding mode (Hidden or Open) 4. App embeds message into image pixels 5. Share through messengers or save locally 6. Recipient opens image in Underlayer to reveal message ENCODING MODES EXPLAINED HIDDEN MODE • Message embedded invisibly in image pixels • Completely undetectable to human eye • Best for uncompressed image sharing • Lost when image is compressed by messengers OPEN MODE • Message encoded as colored frame border • Visible as decorative edge around image • Survives Telegram, WhatsApp compression • Recommended for messenger sharing INTERNATIONAL • Available in English and Russian • More languages coming soon • Automatic language detection Whether you're a privacy enthusiast, security professional, or just curious about steganography - Underlayer makes it accessible to everyone. Download now and start hiding your secrets in plain sight! Terms of use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

About

Phasm

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Hidden in plain sight. Phasm turns ordinary photos into secret messengers. Your photo looks exactly the same — but it carries encrypted messages and files that only someone with the right passphrase can reveal. TWO MODES FOR TWO NEEDS • Ghost Mode — Maximum stealth. Advanced adaptive algorithms make hidden data virtually undetectable, even by statistical analysis tools. Deep Cover auto-activates for non-JPEG photos with ~43% more capacity. Supports file attachments alongside your message. • Armor Mode — Maximum durability. Your hidden message survives recompression, re-encoding, and mild cropping. Fortress sub-mode auto-activates for short messages and handles aggressive compression from popular messaging apps. SERIOUS ENCRYPTION • AES-256-GCM-SIV authenticated encryption — always on, not optional. • Argon2id key derivation — resistant to brute-force and GPU attacks. • Post-quantum safe — 256-bit symmetric keys remain secure against quantum computers. • No backdoors. No key escrow. You hold the only key. PRIVACY BY DESIGN • All processing happens on your device. Nothing is uploaded. • No account. No sign-up. No tracking. No ads. • Open-source Rust cryptographic engine — auditable by anyone. • Built for journalists, researchers, activists, curious tinkerers — or just for fun. ONE PHOTO. MULTIPLE SECRETS. Shadow Messages let you hide several independent messages in a single photo — each locked with its own passphrase. Send the same picture to five friends; each one discovers a different message using their name as the key. Nobody knows the others exist. Under pressure to reveal your passphrase? Hand over the primary one. Your shadow messages stay invisible — no header, no marker, no proof they were ever there. MAGIC WAND — ONE TAP TO OPTIMIZE Tap the wand and your photo is silently tuned for better steganographic embedding. Imperceptible texture is added to smooth regions like skies, bokeh, and flat backgrounds — boosting capacity by 10–35% with no visible change. The photo looks identical. The math works better. SHARE YOUR WAY • Share via AirDrop, Messages, email, or any app that handles images. • phasm.link — generate a short link so recipients can decode instantly in the browser or via App Clip. No install needed. • For guaranteed delivery through messaging apps, use "send as file." BUILT FOR iPHONE AND iPAD • Native app optimized for iPhone and iPad. • Supports JPEG, PNG, GIF, WebP, and HEIC — auto-converted for embedding. • Real-time decode progress with integrity scoring. • 38 languages supported. HONEST ABOUT LIMITATIONS • Platforms that resize or re-encode photos may destroy hidden data. Use direct sharing or "send as file." • 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.

Screenshots

Underlayer4 screens

Verdict

The call

The clearest difference is in-app purchases: Phasm at none against Underlayer's 1. Underlayer's advantage is device support and iOS requirement (15.1 vs 17.0). On price there is nothing between them.

Scored on Price Ā· Rating Ā· Positive reviews Ā· Number of ratings Ā· Update frequency Ā· Ads Ā· In-app purchases Ā· Monetization Ā· Best chart rank Ā· Devices Ā· Requires iOS

CostPrice Ā· In-app purchases Ā· Ads Ā· Monetization

Both are free to download. Underlayer sells 1 in-app purchase, starting at $2.99 per 7 days. Phasm asks for nothing beyond the download.

Scorecard3 real differences Ā· 3 level
Underlayer versus Phasm: the parameters behind the verdict, then further details
ParameterUnderlayerPhasm
PriceFreeFree
Update frequencyEvery 5 months—
AdsYes—
In-app purchasesYesNo — better
DevicesiPhone, iPad, iPod — better—
Requires iOS15.1 — better17.0
Further details — not scored
Size169 MB21 MB
Age rating4+4+
DeveloperMihail RukavishnikovChristoph Gaffga

In-app purchases

1 purchases

Underlayer

Subscriptions1
  • Premium$2.997 Days
None

Phasm

No in-app purchases

Questions

Is Underlayer free?
Underlayer is free to download, with in-app purchases available.
Is Phasm free?
Phasm is free to download, with no in-app purchases.

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