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A whoooole lotta 4.0.x fixes.

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Aaron D. Lee
2026-01-01 22:18:13 -05:00
parent 12929bf326
commit ef7478b30a
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SECURITY.md
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@@ -2,10 +2,12 @@
## Supported Versions
| Version | Supported |
| ------- | ------------------ |
| 2.x.x | :white_check_mark: |
| 1.x.x | :x: |
| Version | Supported | Notes |
| ------- | ------------------ | ----- |
| 4.x.x | ✅ Active | Current release |
| 3.x.x | ⚠️ Security fixes only | Upgrade recommended |
| 2.x.x | ❌ End of life | |
| 1.x.x | ❌ End of life | |
## Reporting a Vulnerability
@@ -34,7 +36,7 @@ Stegasoo is designed to hide the **existence** of a secret message within an ord
| Goal | How It's Achieved |
|------|-------------------|
| **Confidentiality** | AES-256-GCM encryption with Argon2id key derivation |
| **Steganography** | LSB embedding with pseudo-random pixel selection |
| **Steganography** | LSB/DCT embedding with pseudo-random pixel/coefficient selection |
| **Authentication** | Multi-factor: reference photo + passphrase + PIN (or RSA key) |
| **Integrity** | GCM authentication tag detects tampering |
@@ -43,20 +45,43 @@ Stegasoo is designed to hide the **existence** of a secret message within an ord
Stegasoo combines multiple authentication factors:
```
┌─────────────────────────────────────────────────────────────┐
│ Key Derivation │
│ │
│ Reference Photo ─────┐ │
│ (something you have) │ │
│ ├──► Argon2id ──► AES-256 Key │
│ Day Passphrase ──────┤ (256MB RAM) │
│ (something you know) │ │
│ │ │
│ PIN or RSA Key ──────┘ │
│ (second factor) │
└─────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────────┐
│ Key Derivation │
│ │
│ Reference Photo ───────┐ │
│ (something you have) │ │
│ ├──► Argon2id ──► AES-256 Key │
│ Passphrase ────────────┤ (256MB RAM) │
│ (something you know) │ │
│ │ │
│ PIN or RSA Key ────────┘ │
│ (second factor) │
└─────────────────────────────────────────────────────────────────┘
```
## Changes in v4.0
### Removed: Date-Based Key Rotation
**Previous versions (v3.x and earlier):**
- Required a date parameter for encode/decode
- Keys rotated daily based on "day phrase"
- Users had to remember which date they used
**Version 4.0:**
- No date dependency
- Single passphrase (no rotation)
- Simpler but slightly reduced entropy per-message
**Security Impact:**
- Minimal - the date only added ~10 bits of entropy
- Passphrase default increased from 3 to 4 words to compensate (+11 bits)
- Overall entropy remains similar or higher with 4-word default
### Renamed: day_phrase → passphrase
Terminology change only. No security impact.
## What Stegasoo Does NOT Protect Against
### 1. Statistical Steganalysis
@@ -68,7 +93,9 @@ Stegasoo combines multiple authentication factors:
- RS analysis
- Machine learning classifiers
**Mitigation:** Stegasoo uses pseudo-random pixel selection (not sequential), which helps but doesn't eliminate detectability.
**DCT mode is more resilient** but not undetectable.
**Mitigation:** Stegasoo uses pseudo-random pixel/coefficient selection, which helps but doesn't eliminate detectability.
**Recommendation:** Don't rely on Stegasoo if your adversary has:
- Access to the original carrier image
@@ -113,24 +140,28 @@ Stegasoo combines multiple authentication factors:
**Recommendation:**
- Use 8+ digit PINs
- Use 4+ word passphrases
- Use 4+ word passphrases (v4.0 default)
- Consider RSA keys for high-security use cases
### 5. Image Modification
**Risk:** Lossy compression destroys hidden data.
**Data is destroyed by:**
**LSB mode - data is destroyed by:**
- JPEG compression
- Resizing
- Filters/effects
- Screenshots
- Social media upload (Instagram, Twitter, etc.)
- Social media upload
**DCT mode - more resilient but not immune:**
- Survives moderate JPEG recompression
- May fail with aggressive compression (quality < 70)
- Still destroyed by resizing, filters, screenshots
**Recommendation:**
- Always use lossless formats (PNG, BMP)
- Transfer files directly (email, Signal, USB)
- Never upload stego images to social media
- LSB: Always use lossless formats (PNG, BMP), direct transfer
- DCT: Use for social media, but test with your specific platform
### 6. Metadata Leakage
@@ -165,49 +196,52 @@ Stegasoo combines multiple authentication factors:
| Encryption | AES-256-GCM | 12-byte IV, 16-byte tag |
| Photo Hash | SHA-256 | Full image bytes |
### Pixel Selection
### Pixel/Coefficient Selection
Pixels are selected pseudo-randomly using a key derived from:
Selection key is derived from:
```
pixel_key = SHA256(photo_hash || passphrase || date || pin/rsa_signature)
selection_key = SHA256(photo_hash || passphrase || pin/rsa_signature)
```
This prevents:
- Sequential embedding patterns
- Statistical detection of modified regions
### Format
### Message Format (v4.0)
```
┌──────────────────────────────────────────────────────────────┐
│ Magic (4B) │ Version (1B) │ Date (10B) │ Salt (32B) │ IV (12B) │
├──────────────────────────────────────────────────────────────┤
│ Encrypted Payload (AES-256-GCM) │
│ ├── Type (1B): 0x01=text, 0x02=file │
│ ├── Length (4B) │
│ ├── Data (variable) │
│ └── [Filename if file] (variable) │
├──────────────────────────────────────────────────────────────┤
│ GCM Auth Tag (16B) │
└──────────────────────────────────────────────────────────────┘
┌──────────────────────────────────────────────────────────────────┐
│ Magic (4B) │ Version (1B) │ Salt (32B) │ IV (12B) │
├──────────────────────────────────────────────────────────────────┤
│ Encrypted Payload (AES-256-GCM) │
│ ├── Type (1B): 0x01=text, 0x02=file │
│ ├── Length (4B) │
│ ├── Data (variable) │
│ └── [Filename if file] (variable) │
├──────────────────────────────────────────────────────────────────┤
│ GCM Auth Tag (16B) │
└──────────────────────────────────────────────────────────────────┘
```
**Note:** v4.0 removed the date field from the header, reducing overhead by 10 bytes.
## Best Practices
### For Maximum Security
1. **Use RSA keys** instead of PINs for authentication
2. **Use unique reference photos** not available online
3. **Use long passphrases** (4+ random words)
3. **Use long passphrases** (4+ random words, recommend 6+)
4. **Transfer via secure channels** (Signal, encrypted email)
5. **Delete stego images** after message is read
6. **Keep software updated** for security fixes
7. **Use DCT mode** for social media sharing
### For Casual Privacy
1. **6-digit PIN** is sufficient for non-adversarial use
2. **3-word passphrase** provides reasonable security
3. **PNG format** always for output
2. **4-word passphrase** provides reasonable security (v4.0 default)
3. **PNG format** for LSB mode output
4. **Direct file transfer** (email attachment, AirDrop)
## Known Limitations
@@ -216,8 +250,8 @@ This prevents:
|------------|--------|--------|
| LSB is detectable | Statistical analysis can detect hidden data | By design (tradeoff for capacity) |
| No forward secrecy | Compromised key decrypts all messages | Use different keys per message for high security |
| Date in header | Reveals when message was encoded | By design (enables day-specific passphrases) |
| No deniability | Single password = single message | Future: plausible deniability layers |
| Python 3.13 incompatible | jpegio C extension crashes | Use Python 3.12 or earlier |
## Security Audit Status
@@ -231,6 +265,9 @@ If you're a security researcher interested in auditing Stegasoo, please reach ou
| Version | Security Changes |
|---------|------------------|
| 4.0.0 | Removed date dependency, increased default passphrase to 4 words, added JPEG normalization |
| 3.2.0 | DCT color mode added |
| 3.0.0 | Added DCT steganography mode |
| 2.2.0 | Added compression (no security impact) |
| 2.1.0 | Upgraded to Argon2id, increased iterations |
| 2.0.0 | Added RSA key support |