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The Crypter class handles encryption and decryption of Phasmophobia save files using AES-CBC encryption with PBKDF2 key derivation.

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Namespace

PhasmoDecrypt.Crypter

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Methods

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Decrypt()

Decrypts an encrypted Phasmophobia save file and returns formatted JSON. 
public string Decrypt(byte[] data)
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data
byte[]
required
The encrypted save file data as a byte array. Must include the 16-byte IV prefix.
Returns: string - The decrypted JSON data formatted with indentation, or an error message if decryption fails. Algorithm Details:
  • Extracts the first 16 bytes as the Initialization Vector (IV)
  • Uses PBKDF2 (RFC 2898) with SHA1 hash algorithm
  • Derives a 16-byte AES key using 100 iterations
  • Secret key: "t36gref9u84y7f43g" (from Globals.Save_Secret)
  • Decrypts using AES-CBC mode with PKCS7 padding
  • Parses and formats the resulting JSON
Example Usage: 
var crypter = new Crypter();
byte[] encryptedData = File.ReadAllBytes("SaveFile.txt");
string decryptedJson = crypter.Decrypt(encryptedData);

if (decryptedJson.StartsWith("Error:") || decryptedJson.StartsWith("check"))
{
    Console.WriteLine("Decryption failed: " + decryptedJson);
}
else
{
    File.WriteAllText("SaveFile_Decrypted.json", decryptedJson);
}
Error Handling:
  • Returns "Error: Data is null or empty." if input is null or empty
  • Returns "check the correctness of the file: {exception}" if JSON parsing fails
The method automatically formats the decrypted JSON with indentation for readability.

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EncryptData()

Encrypts JSON data for use as a Phasmophobia save file. 
public byte[] EncryptData(string data)
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data
string
required
The JSON string to encrypt (typically modified save file data).
Returns: byte[] - The encrypted data with the IV prepended as the first 16 bytes. Algorithm Details:
  • Generates a random 16-byte Initialization Vector (IV) using RandomNumberGenerator
  • Uses PBKDF2 (RFC 2898) with SHA1 hash algorithm
  • Derives a 16-byte AES key using 100 iterations
  • Secret key: "t36gref9u84y7f43g" (from Globals.Save_Secret)
  • Encrypts using AES-CBC mode with PKCS7 padding
  • Prepends the IV to the encrypted data
Example Usage: 
var crypter = new Crypter();
string modifiedJson = File.ReadAllText("SaveFile_Decrypted.json");
byte[] encryptedData = crypter.EncryptData(modifiedJson);
File.WriteAllBytes("SaveFile_Encrypted.txt", encryptedData);
Output Format: 
[16-byte IV][Encrypted Data]
The output must be written as binary data. Do not convert to text or the save file will be corrupted.

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Encryption Implementation

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Key Derivation

Both methods use PBKDF2 for key derivation: 
var dbytes = new Rfc2898DeriveBytes(
    Globals.Save_Secret,  // "t36gref9u84y7f43g"
    iv,                   // 16-byte salt (IV)
    100,                  // Iteration count
    HashAlgorithmName.SHA1
);
var key = dbytes.GetBytes(16);  // 128-bit AES key

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AES Configuration

using var aes = Aes.Create();
aes.Mode = CipherMode.CBC;
aes.Padding = PaddingMode.PKCS7;
aes.Key = key;  // 16 bytes (128-bit)
aes.IV = iv;    // 16 bytes

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Dependencies

  • System.Security.Cryptography - For AES and PBKDF2
  • Newtonsoft.Json - For JSON parsing and formatting
  • PhasmoDecrypt.Globals - For the encryption secret key

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Source Reference

See the full implementation: /workspace/source/Classes/Crypter.cs:14-86

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