Smart Password Manager C#: release v4.0.0

BREAKING CHANGE: Update to smartpasslib-csharp v4.0.0

Core changes:
- Dynamic iterations: 15-30 (private), 45-60 (public)
- Google-compatible charset (26 special chars + A-Z + a-z + 0-9)
- Password length: 12-100 (was 12-1000)
- Secret validation: min 12 chars (enforced)
- Salt separation: "private"/"public" for key isolation

Forms updated:
- AddPasswordForm: length range 12-100, secret min 12
- EditPasswordForm: length range 12-100
- GetPasswordForm: secret validation min 12
- AboutForm: version 4.0.0
- QRCodeForm: uses new SmartPassword format
- Export: lib_version uses SmartPasswordGenerator.Version

Documentation:
- README updated to v4.0.0
- Add MIGRATION.md

Version note: v1.x.x -> v4.0.0 (align with smartpasslib-csharp v4.0.0)

Author: smartlegionlab

MIGRATION.md

@@ -0,0 +1,118 @@
+# Migration Guide: v1.x.x to v4.0.0
+
+> **📌 Version Note:** SmartPasswordManagerCsharpDesktop jumps from v1.x.x directly to v4.0.0 to align with smartpasslib-csharp v4.0.0. All smartpasslib implementations (Python, C#, JS, Go, Kotlin) now share the same version number and algorithm.
+
+## ⚠️ Breaking Change Notice
+
+**SmartPasswordManagerCsharpDesktop v4.0.0 is NOT backward compatible with v1.x.x**
+
+| Version    | Status      | Why                                                              |
+|------------|-------------|------------------------------------------------------------------|
+| v1.x.x     | Deprecated  | Fixed iterations (30/60), limited character set                  |
+| **v4.0.0** | **Current** | Dynamic iterations (15-30/45-60), expanded charset, max security |
+
+Smart passwords generated with v1.x.x cannot be regenerated using v4.0.0 due to fundamental changes in the deterministic generation algorithm.
+
+---
+
+## Why the change?
+
+**v4.0.0 introduces fundamental improvements:**
+
+- **Dynamic iteration counts** — deterministic steps vary per secret (15-30 for private, 45-60 for public)
+- **Expanded character set** — Google-compatible symbols
+- **Enhanced key derivation** — salt separation for public/private keys ("private"/"public")
+- **Unified length validation** — password length must be 12-100 characters (was 12-1000)
+- **Input validation** — secret phrases must be at least 12 characters (enforced)
+- **Maximum security** — no secret exposure in logs or iterations
+
+---
+
+## What changed in the Desktop Manager:
+
+| Aspect                 | v1.x.x             | v4.0.0                                |
+|------------------------|--------------------|---------------------------------------|
+| Private key iterations | Fixed 30           | Dynamic 15-30                         |
+| Public key iterations  | Fixed 60           | Dynamic 45-60                         |
+| Character set          | `abc...!@#$&*-_`   | `!@#$%^&*()_+-=[]{};:,.<>?/A-Za-z0-9` |
+| Password max length    | 1000               | 100                                   |
+| Secret validation      | None (min 4 chars) | Min 12 characters (enforced)          |
+| Key derivation salt    | None               | "private"/"public"                    |
+| Secret in iterations   | Yes (exposed)      | No (secure)                           |
+
+---
+
+## Metadata File Compatibility
+
+**The old `passwords.json` file is NOT compatible with v4.0.0**
+
+Public keys stored in v1.x.x files cannot be used with v4.0.0 because:
+- Iteration counts changed from fixed 60 to dynamic 45-60
+- Salt "public" was added to key derivation
+
+**Result:** Old entries will load but secret verification will fail. Passwords cannot be regenerated.
+
+---
+
+## Migration Steps
+
+### Step 1: Retrieve existing passwords using old version
+
+Before upgrading, retrieve all actual passwords from v1.x.x:
+- Open the old version of the application
+- For each entry, click **Get** and copy the password
+- Save all retrieved passwords in a safe place
+
+### Step 2: Backup old metadata file
+
+The old metadata file is located at `%USERPROFILE%\.config\smart_password_manager\passwords.json`
+
+Copy this file to a safe location (e.g., `passwords.json.v1.bak`).
+
+### Step 3: Upgrade to v4.0.0
+
+Download the new binary or build from source. Replace the old executable.
+
+### Step 4: Remove old metadata file
+
+The old metadata file must be removed or moved away from the default location. v4.0.0 will create a new empty file on first run.
+
+### Step 5: Re-add entries
+
+Launch the application and add all entries again using the **same secret phrases and lengths** as before.
+
+### Step 6: Update services
+
+Replace old passwords (from Step 1) with newly generated ones on each website/service.
+
+### Step 7: Verify
+
+Log in using new passwords. Confirm regeneration works (same secret → same password).
+
+---
+
+## Important Notes
+
+- **No automatic migration** — manual password regeneration required
+- **No database migration** — old metadata file is incompatible
+- **Your secret phrases remain the same** — use them to recreate entries
+- **Secret phrases shorter than 12 characters will now be rejected**
+- **Password lengths between 101 and 1000 will now be rejected**
+- **Old passwords still work** on services until you change them
+- Test with non-essential accounts first
+
+---
+
+## Rollback
+
+If you need to rollback to v1.x.x, use the old binary and restore your backup metadata file.
+
+---
+
+## Need Help?
+
+- **Issues**: [GitHub Issues](https://github.com/smartlegionlab/SmartPasswordManagerCsharpDesktop/issues)
+- **Core Library Issues**: [smartpasslib Issues](https://github.com/smartlegionlab/smartpasslib/issues)
+
+---
+

README.md

@@ -1,4 +1,4 @@
-# Smart Password Manager Desktop (C#) <sup>v1.1.5</sup>
+# Smart Password Manager Desktop (C#) <sup>v4.0.0</sup>
 
 ---
 
@@ -29,6 +29,22 @@ Smart Password Manager stores nothing. Your secrets never leave your device. Pas
 
 ---
 
+## 🔄 Breaking Change (v4.0.0)
+
+> **⚠️ This version uses [smartpasslib-csharp](https://github.com/smartlegionlab/smartpasslib-csharp) v4.0.0, which is NOT backward compatible with v1.x.x**
+
+Smart passwords created with older versions **cannot be regenerated** with v4.0.0.
+
+**What changed:**
+- Dynamic iterations: private key 15-30 steps (was fixed 30), public key 45-60 steps (was fixed 60)
+- Expanded Google-compatible character set
+- Secret phrases now require minimum 12 characters (was 4)
+- Password length now limited to 100 characters (was 1000)
+
+📖 **Full migration instructions** → see [MIGRATION.md](https://github.com/smartlegionlab/SmartPasswordManagerCsharpDesktop/blob/master/MIGRATION.md)
+
+---
+
 ## Core Principles
 
 - **Zero-Storage Security**: No passwords or secret phrases are ever stored or transmitted
@@ -42,7 +58,7 @@ Smart Password Manager stores nothing. Your secrets never leave your device. Pas
 
 - **Decentralized & Serverless**: No central database, no cloud lock-in, complete user sovereignty
 - **Smart Password Generation**: Deterministic from secret phrase
-- **Public/Private Key System**: 30 iterations for private key, 60 for public key
+- **Dynamic Key Derivation**: 15-30 iterations for private key, 45-60 for public key (deterministic per secret)
 - **Secret Verification**: Verify secret without exposing it
 - **Dark Theme Interface**: Easy on the eyes during extended use
 - **Full CRUD Operations**: Create, Read, Update, Delete
@@ -75,14 +91,21 @@ Smart Password Manager stores nothing. Your secrets never leave your device. Pas
 
 Powered by **[smartpasslib-csharp](https://github.com/smartlegionlab/smartpasslib-csharp)** — C# implementation of deterministic password generation.
 
-**Key derivation (same as Python/JS/Kotlin/Go/C# versions):**
+**Key derivation (same as Python/JS/Kotlin/Go versions v4.0.0):**
 
-| Key Type    | Iterations | Purpose                                               |
-|-------------|------------|-------------------------------------------------------|
-| Private Key | 30         | Password generation (never stored, never transmitted) |
-| Public Key  | 60         | Verification (stored locally)                         |
+| Key Type    | Iterations              | Purpose                                               |
+|-------------|-------------------------|-------------------------------------------------------|
+| Private Key | 15-30 (dynamic)         | Password generation (never stored, never transmitted) |
+| Public Key  | 45-60 (dynamic)         | Verification (stored locally)                         |
 
-**Character Set:** `abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789!@#$&*-_`
+**Character Set (Google-compatible):**
+```
+!@#$%^&*()_+-=[]{};:,.<>?/ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz
+```
+
+**Validation Rules:**
+- Secret phrase: minimum 12 characters
+- Password length: 12-100 characters
 
 **Decentralized Architecture**:
 - No central authority required
@@ -169,10 +192,13 @@ The application allows you to export password metadata to the **Smart Password M
 ### Secret Phrase
 - **Minimum 12 characters** (enforced)
 - Case-sensitive
-- Use mix of: uppercase, lowercase, numbers, symbols, emoji, or Cyrillic
+- Use mix of: uppercase, lowercase, numbers, symbols
 - Never store digitally
 - **NEVER use your password description as secret phrase**
 
+### Password Length Requirements
+- **Smart passwords**: 12-100 characters
+
 ### Strong Secret Examples
 ```
 ✅ "MyStrongSecretPhrase2026!"   — mixed case + numbers + symbols
@@ -182,11 +208,12 @@ The application allows you to export password metadata to the **Smart Password M
 
 ### Weak Secret Examples (avoid)
 ```
+❌ "short"                       — too short, rejected
 ❌ "GitHub Account"              — using description as secret (weak!)
 ❌ "password"                    — dictionary word, too short
 ❌ "1234567890"                  — only digits, too short
 ❌ "qwerty123"                   — keyboard pattern
-❌ Same as description           — never use the same value as password description
+❌ Same as description           — never use the same value as description
 ```
 
 ### Decentralized Nature
@@ -251,6 +278,13 @@ Smart Password Manager Desktop (C#) produces **identical passwords** to:
 - **[Web Smart Password Manager](https://github.com/smartlegionlab/smart-password-manager-web)**
 - **[Android Smart Password Manager](https://github.com/smartlegionlab/smart-password-manager-android)**
 
+## Version History
+
+| Version          | smartpasslib-csharp | Status                   | Migration Required     |
+|------------------|---------------------|--------------------------|------------------------|
+| v1.x.x and below | v1.x.x              | ❌ Deprecated/Unsupported | Must migrate to v4.x.x |
+| **v4.0.0+**      | **v4.0.0+**         | ✅ Current                | N/A                    |
+
 ## License
 
 **[BSD 3-Clause License](https://github.com/smartlegionlab/SmartPasswordManagerCsharpDesktop/blob/master/LICENSE)**
@@ -268,3 +302,5 @@ Copyright (©) 2026, [Alexander Suvorov](https://github.com/smartlegionlab)
 - **Issues**: [GitHub Issues](https://github.com/smartlegionlab/SmartPasswordManagerCsharpDesktop/issues)
 - **Documentation**: This [README](https://github.com/smartlegionlab/SmartPasswordManagerCsharpDesktop/blob/master/README.md)
 
+---
+

SmartPasswordManagerCsharpDesktop/Forms/AboutForm.cs

@@ -59,7 +59,7 @@ private void InitializeComponent()
 
         contentPanel.Controls.Add(new Label
         {
-            Text = $"Version v1.1.5 | .NET 10.0 | Windows",
+            Text = $"Version v4.0.0 | .NET 10.0 | Windows",
             Font = new Font("Segoe UI", 10),
             ForeColor = Color.FromArgb(160, 160, 170),
             TextAlign = ContentAlignment.MiddleCenter,

SmartPasswordManagerCsharpDesktop/Forms/MainForm.cs

@@ -616,10 +616,10 @@ private void ExportPasswords()
                     {
                         ["exported_at"] = DateTime.Now.ToString("yyyy-MM-ddTHH:mm:ss"),
                         ["app_name"] = "Smart Password Manager C# Desktop",
-                        ["app_version"] = "v1.1.5",
+                        ["app_version"] = "v4.0.0",
                         ["app_type"] = "Desktop",
                         ["lib_name"] = "smartpasslib-csharp",
-                        ["lib_version"] = "v1.0.5",
+                        ["lib_version"] = "v4.0.0",
                         ["lib_lang"] = "C#",
                         ["count"] = _manager.PasswordCount
                     };
@@ -858,7 +858,7 @@ private string GetHelpText()
 "  • Use emoji or non-Latin characters for stronger secrets\n\n" +
 
 "══════════════════════════════════════════════════════════════════════════════\n" +
-"  Version v1.1.5 | Copyright © 2026 Alexander Suvorov\n" +
+"  Version v4.0.0 | Copyright © 2026 Alexander Suvorov\n" +
 "  Licensed under BSD 3-Clause License | https://github.com/smartlegionlab\n" +
 "══════════════════════════════════════════════════════════════════════════════";
     }