Add README.md to document registration key generation algorithm

README.md

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+# Registration Key Algorithm
+
+This document describes the registration key generation algorithm found in `app/src/main/java/bH/C0997e.java`.
+
+## Overview
+
+The algorithm generates registration keys for product licensing using a multi-step process that combines user information, applies various transformations, and generates a cryptographic hash.
+
+## Algorithm Steps
+
+### Method 1: Basic Obfuscation
+`a(String str, String str2, String str3, String str4)`
+
+Parameters:
+- `str` - First name
+- `str2` - Last name  
+- `str3` - Product name
+- `str4` - Email address
+
+**Process:**
+
+1. **Input Validation** - Check all parameters are non-null and non-empty
+
+2. **Concatenation** - Create byte array by concatenating:
+   ```
+   lastName + productName + firstName + lastName + email
+   ```
+
+3. **Byte Reversal** - Reverse the entire byte array
+   ```java
+   for (int i = 0; i < bArr.length / 2; i++) {
+       byte temp = bArr[i];
+       bArr[i] = bArr[(bArr.length - 1) - i];
+       bArr[(bArr.length - 1) - i] = temp;
+   }
+   ```
+
+4. **Character Transformation** - Apply mathematical formula to each byte:
+   ```java
+   for (int i = 0; i < bArr.length; i++) {
+       byte b = bArr[i];
+       int transformed = (b + ((b - 32) % 7)) - (i % 4);
+       if (transformed > 122) {
+           transformed -= 9;
+       }
+       bArr[i] = (byte) transformed;
+   }
+   ```
+
+5. **Special Character Handling** - Modify specific ASCII codes:
+   ```java
+   for (int i = 0; i < bArr.length; i++) {
+       if (bArr[i] == 96 || bArr[i] == 92 || bArr[i] == 91 || 
+           bArr[i] == 93 || bArr[i] == 59 || bArr[i] == 46) {
+           bArr[i] = (byte) (bArr[i] + 6 + (i % 10));
+       }
+   }
+   ```
+   Special characters affected: `` ` `` (96), `\` (92), `[` (91), `]` (93), `;` (59), `.` (46)
+
+6. **Return** - Convert byte array to string
+
+### Method 2: Registration Key Generation (5 Parameters)
+`a(String str, String str2, String str3, String str4, String str5)`
+
+Parameters:
+- `str` - First name
+- `str2` - Last name
+- `str3` - Product name
+- `str4` - Secret/seed value
+- `str5` - Email address
+
+**Process:**
+
+1. **Get Obfuscated String** - Call Method 1 to get obfuscated base string
+
+2. **MD5 Hashing** - Create MD5 hash:
+   ```java
+   MessageDigest md5 = MessageDigest.getInstance("MD5");
+   byte[] input = (obfuscatedString + secret).getBytes();
+   md5.update(input);
+   md5.update(input);  // Update twice
+   md5.digest();       // Digest once (discarded)
+   md5.update(input);  // Update again
+   byte[] hash = md5.digest();  // Final digest
+   ```
+
+3. **Checksum Generation** - Create 4-byte checksum using custom algorithm
+
+4. **Combine Checksum and Hash**:
+   ```
+   result = checksum (4 bytes) + hash (16 bytes) = 20 bytes total
+   ```
+
+5. **Base-32 Encoding** - Convert to custom base-32 string:
+   ```
+   Charset: "123456789ABCDEFGHIJKLMNPQRSTUVWXYZ" (33 characters, no 'O')
+   ```
+   Each byte is mapped to a character: `char = charset[abs(byte) % 33]`
+
+### Method 3: Enhanced Registration Key (7 Parameters)
+`a(String str, String str2, String str3, String str4, String str5, String str6, String str7)`
+
+Additional parameters:
+- `str6` - Additional field 1
+- `str7` - Additional field 2
+
+**Changes from Method 2:**
+
+1. **Lowercase Conversion** - firstName, lastName, and email are converted to lowercase
+
+2. **Extended Base String**:
+   ```
+   obfuscated(firstName.toLowerCase(), lastName.toLowerCase(), product, email.toLowerCase()) + field1 + field2
+   ```
+
+3. **Modified MD5 Process**:
+   ```java
+   md5.update(input);
+   md5.update(input);
+   md5.update((input + field1).getBytes());  // Additional update with field1
+   byte[] hash = md5.digest();
+   ```
+
+4. **Different Character Set**:
+   ```
+   Charset: "23456789ABCDEFGHJKLMNPQRSTUVWXYZ" (31 characters, no '1', 'I', 'O')
+   char = charset[abs(byte) % 31]
+   ```
+
+### Method 4: Full Registration Key (8 Parameters)
+`a(String str, String str2, String str3, String str4, String str5, String str6, String str7, String str8)`
+
+Additional parameter:
+- `str8` - Additional field 3
+
+**Changes:**
+
+- Base string includes all three additional fields: `field1 + field2 + field3`
+- Same character set as Method 3
+
+## Usage Context
+
+The registration dialog calls these methods (found in `app/src/main/java/ao/dQ.java`):
+
+```java
+String calculatedKey = C0997e.a(firstName, lastName, "MegaLogViewer", email);
+
+if (calculatedKey != null && calculatedKey.equals(userEnteredKey) && !alreadyRegistered(userEnteredKey)) {
+    // Registration successful
+}
+```
+
+## Key Properties
+
+- **Character Sets**: Custom base-32 encoding (excludes ambiguous characters like 'O', '1', 'I')
+- **Output Length**: 20 characters (from 20 bytes)
+- **Hash Algorithm**: MD5
+- **Deterministic**: Same inputs always produce same key
+- **Case Handling**: Methods 3 & 4 normalize to lowercase for consistency
+
+## Security Notes
+
+- Uses MD5 hashing (considered weak by modern standards)
+- Obfuscation through byte manipulation
+- No salt/random component (deterministic output)
+- Multiple hash iterations for additional complexity
+- Custom encoding prevents simple reverse engineering