Video Encryption SDK - Interface Reference¶

Overview¶

The Video Encryption SDK provides COM interfaces for encrypting and decrypting MP4 video files with AES-256 encryption. This reference covers all interfaces, methods, and helper classes for C++, C#, and Delphi developers.

IVFCryptoConfig Interface¶

Primary interface for configuring encryption passwords and keys on both the encryption muxer and decryption demuxer filters.

Interface GUID¶

{BAA5BD1E-3B30-425e-AB3B-CC20764AC253}

Inheritance¶

Inherits from `IUnknown`¶

Interface Definitions¶

C++ Definition¶

#include "encryptor_intf.h"

// {BAA5BD1E-3B30-425e-AB3B-CC20764AC253}
DEFINE_GUID(IID_ICryptoConfig,
    0xbaa5bd1e, 0x3b30, 0x425e, 0xab, 0x3b, 0xcc, 0x20, 0x76, 0x4a, 0xc2, 0x53);

DECLARE_INTERFACE_(ICryptoConfig, IUnknown)
{
    STDMETHOD(put_Provider)(THIS_ IPasswordProvider* pProvider) PURE;
    STDMETHOD(get_Provider)(THIS_ IPasswordProvider** ppProvider) PURE;
    STDMETHOD(put_Password)(THIS_ LPBYTE pBuffer, LONG lSize) PURE;
    STDMETHOD(HavePassword)(THIS_) PURE;
};

C# Definition¶

using System;
using System.Runtime.InteropServices;

[ComImport]
[Guid("BAA5BD1E-3B30-425e-AB3B-CC20764AC253")]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IVFCryptoConfig
{
    [PreserveSig]
    int put_Provider([In] IVFPasswordProvider passwordProviderNotUsed);

    [PreserveSig]
    int get_Provider([Out] IVFPasswordProvider passwordProviderNotUsed);

    [PreserveSig]
    int put_Password(IntPtr buffer, [In] int size);

    [PreserveSig]
    int HavePassword();
}

Delphi Definition¶

type
  IVFCryptoConfig = interface(IUnknown)
    ['{BAA5BD1E-3B30-425e-AB3B-CC20764AC253}']
    function put_Provider(passwordProviderNotUsed: TObject): HRESULT; stdcall;
    function get_Provider(out passwordProviderNotUsed: TObject): HRESULT; stdcall;
    function put_Password(buffer: PWideChar; size: integer): HRESULT; stdcall;
    function HavePassword(): HRESULT; stdcall;
  end;

Methods¶

put_Provider¶

Sets a password provider callback interface for advanced encryption scenarios. C++ Syntax:

HRESULT put_Provider(IPasswordProvider* pProvider);

C# Syntax:

int put_Provider(IVFPasswordProvider passwordProvider);

Parameters: - pProvider / passwordProvider - Password provider interface that implements IVFPasswordProvider Return Value: - S_OK (0) on success - Error HRESULT on failure Remarks: Use this method for advanced scenarios where you need: - Dynamic password generation based on file name - Binary key data provision through a callback - Custom key derivation functions - File-specific encryption keys - Per-file password policies For simple string passwords, using put_Password directly is more straightforward. The password provider is useful when you need runtime password determination or when implementing a custom key management system. Example Use Cases: 1. Binary Key Provider: Provide 256-bit encryption keys from a key management system 2. Dynamic Passwords: Generate different passwords based on file names or metadata 3. Key Derivation: Implement custom key derivation functions (PBKDF2, Argon2, etc.) 4. Secure Storage Integration: Retrieve keys from hardware security modules (HSM) or key vaults

get_Provider¶

Gets the currently set password provider interface.

C++ Syntax:

HRESULT get_Provider(IPasswordProvider** ppProvider);

C# Syntax:

int get_Provider(IVFPasswordProvider passwordProvider);

Parameters: - ppProvider / passwordProvider - Pointer to receive password provider interface

Return Value: - S_OK (0) on success - E_POINTER if ppProvider is NULL - Error HRESULT on failure

Remarks: Retrieves the password provider interface that was previously set with put_Provider. Returns NULL if no provider has been set.

put_Password¶

Sets the encryption password or binary key data. C++ Syntax:

HRESULT put_Password(LPBYTE pBuffer, LONG lSize);

C# Syntax:

int put_Password(IntPtr buffer, int size);

Delphi Syntax:

function put_Password(buffer: PWideChar; size: integer): HRESULT; stdcall;

Parameters: - pBuffer / buffer - Pointer to password or binary key data - lSize / size - Size of buffer in bytes Return Value: - S_OK (0) on success - E_INVALIDARG if buffer is null or size is invalid - Error HRESULT on failure Remarks: - The SDK uses AES-256 encryption, which requires a 256-bit (32-byte) key - If you provide a password string, it should be hashed to 256 bits (use SHA-256) - The same password/key must be used for both encryption and decryption - For string passwords, use the helper methods (C# only) or hash manually - Binary data is hashed with SHA-256 internally to generate the encryption key Example (C++):

ICryptoConfig* pCrypto = nullptr;
hr = pMuxer->QueryInterface(IID_ICryptoConfig, (void**)&pCrypto);
if (SUCCEEDED(hr))
{
    // Using string password (must convert to proper format)
    const wchar_t* password = L"MySecurePassword123";
    hr = pCrypto->put_Password(
        (LPBYTE)password,
        wcslen(password) * sizeof(wchar_t)
    );
    pCrypto->Release();
}

Example (C#):

var cryptoConfig = muxerFilter as IVFCryptoConfig;
if (cryptoConfig != null)
{
    // Using helper method (recommended)
    cryptoConfig.ApplyString("MySecurePassword123");
    // Or manually with IntPtr
    string password = "MySecurePassword123";
    IntPtr ptr = Marshal.StringToCoTaskMemUni(password);
    try
    {
        cryptoConfig.put_Password(ptr, password.Length * 2);
    }
    finally
    {
        Marshal.FreeCoTaskMem(ptr);
    }
}

Example (Delphi):

var
  CryptoConfig: IVFCryptoConfig;
  Password: WideString;
begin
  if Supports(MuxerFilter, IVFCryptoConfig, CryptoConfig) then
  begin
    Password := 'MySecurePassword123';
    CryptoConfig.put_Password(PWideChar(Password), Length(Password) * 2);
  end;
end;

HavePassword¶

Checks whether a password has been set on the filter.

C++ Syntax:

HRESULT HavePassword();

C# Syntax:

int HavePassword();

Delphi Syntax:

function HavePassword(): HRESULT; stdcall;

Parameters: None

Return Value: - S_OK (0) if password is set - S_FALSE (1) if no password is set - Error HRESULT on failure

Remarks: Use this method to verify that a password has been configured before starting the filter graph.

Example (C++):

ICryptoConfig* pCrypto = nullptr;
hr = pMuxer->QueryInterface(IID_ICryptoConfig, (void**)&pCrypto);
if (SUCCEEDED(hr))
{
    HRESULT hrPassword = pCrypto->HavePassword();
    if (hrPassword == S_OK)
    {
        // Password is set, can start encoding
    }
    else
    {
        // No password set
        MessageBox(NULL, L"Please set encryption password", L"Error", MB_OK);
    }

    pCrypto->Release();
}

Example (C#):

var cryptoConfig = muxerFilter as IVFCryptoConfig;
if (cryptoConfig != null)
{
    int hr = cryptoConfig.HavePassword();
    if (hr == 0) // S_OK
    {
        // Password is set
        Console.WriteLine("Password configured successfully");
    }
    else
    {
        // No password
        Console.WriteLine("Warning: No password set");
    }
}

IVFPasswordProvider Interface¶

Callback interface for advanced password provision scenarios including binary key data, dynamic password generation, and custom key derivation functions.

Interface GUID¶

{6F8162B5-778D-42b5-9242-1BBABB24FFC4}

Inheritance¶

Inherits from `IUnknown`¶

Interface Definitions¶

C++ Definition¶

// {6F8162B5-778D-42b5-9242-1BBABB24FFC4}
DEFINE_GUID(IID_IPasswordProvider,
    0x6f8162b5, 0x778d, 0x42b5, 0x92, 0x42, 0x1b, 0xba, 0xbb, 0x24, 0xff, 0xc4);

DECLARE_INTERFACE_(IPasswordProvider, IUnknown)
{
    STDMETHOD(QueryPassword)(
        THIS_
        LPCWSTR pszFileName,
        LPBYTE pBuffer,
        LONG* plSize
    ) PURE;
};

C# Definition¶

[ComImport]
[Guid("6F8162B5-778D-42b5-9242-1BBABB24FFC4")]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IVFPasswordProvider
{
    [PreserveSig]
    int QueryPassword(
        [MarshalAs(UnmanagedType.LPWStr)] string pszFileName,
        [In, Out, MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 2)] byte[] pBuffer,
        [In, Out] ref int plSize
    );
}

Methods¶

QueryPassword¶

Called by the filter to query the password or binary key data for a specific file. C++ Syntax:

HRESULT QueryPassword(
    LPCWSTR pszFileName,
    LPBYTE pBuffer,
    LONG* plSize
);

C# Syntax:

int QueryPassword(
    string pszFileName,
    byte[] pBuffer,
    ref int plSize
);

Parameters: - pszFileName - File name for which password is requested (can be used to determine file-specific keys) - pBuffer - Buffer to receive password data or binary key - plSize - Pointer to buffer size (input: max buffer size, output: actual data size returned) Return Value: - S_OK (0) if password provided successfully - E_OUTOFMEMORY if buffer is too small (set plSize to required size) - Error HRESULT on failure Remarks: Implement this interface to: - Provide binary key data (256-bit keys for AES-256) - Generate file-specific encryption keys based on file name - Retrieve keys from external key management systems - Implement custom password derivation logic For simple scenarios with a single password for all files, using IVFCryptoConfig::put_Password directly is more straightforward. Implementation Example (C#):

public class CustomPasswordProvider : IVFPasswordProvider
{
    public int QueryPassword(string pszFileName, byte[] pBuffer, ref int plSize)
    {
        // Generate file-specific key
        byte[] key = GenerateKeyForFile(pszFileName);
        if (pBuffer == null || plSize < key.Length)
        {
            plSize = key.Length;
            return unchecked((int)0x8007000E); // E_OUTOFMEMORY
        }
        Array.Copy(key, pBuffer, key.Length);
        plSize = key.Length;
        return 0; // S_OK
    }
    private byte[] GenerateKeyForFile(string fileName)
    {
        // Custom key generation logic
        using (var sha256 = SHA256.Create())
        {
            string seed = "MySalt" + fileName;
            return sha256.ComputeHash(Encoding.UTF8.GetBytes(seed));
        }
    }
}

C# Helper Methods¶

The SDK provides convenient extension methods for C# developers in the VFCryptoConfigHelper class.

ApplyString¶

Applies a string password with automatic SHA-256 hashing.

Syntax:

public static int ApplyString(this IVFCryptoConfig cryptoConfig, string key)

Parameters: - cryptoConfig - The IVFCryptoConfig interface instance - key - String password to apply

Return Value: - 0 on success - Throws Exception if key is null or empty

Remarks: - Automatically converts string to Unicode and applies SHA-256 hashing - Most common method for setting passwords - Ensures consistent password format across encryption/decryption

Example:

var cryptoConfig = muxerFilter as IVFCryptoConfig;
if (cryptoConfig != null)
{
    cryptoConfig.ApplyString("MySecurePassword123");
}

ApplyFile¶

Uses a file's content as the encryption key (SHA-256 hash of file). Syntax:

public static int ApplyFile(this IVFCryptoConfig cryptoConfig, string key)

Parameters: - cryptoConfig - The IVFCryptoConfig interface instance - key - Path to file to use as encryption key Return Value: - 0 on success - Throws FileNotFoundException if file doesn't exist - Throws Exception if key is null or empty Remarks: - Reads entire file content and computes SHA-256 hash - Useful for using key files or certificates as encryption keys - File content is never stored, only the hash - Same file must be used for both encryption and decryption Example:

var cryptoConfig = muxerFilter as IVFCryptoConfig;
if (cryptoConfig != null)
{
    cryptoConfig.ApplyFile(@"C:\keys\encryption.key");
}

Security Note: - Store key files securely - Use appropriate file permissions - Consider using dedicated key storage systems for production

ApplyBinary¶

Applies binary key data with automatic SHA-256 hashing.

Syntax:

public static int ApplyBinary(this IVFCryptoConfig cryptoConfig, byte[] key)

Parameters: - cryptoConfig - The IVFCryptoConfig interface instance - key - Binary key data (any length)

Return Value: - 0 on success - Throws Exception if key is null or empty

Remarks: - Accepts binary key data of any length - Automatically computes SHA-256 hash to generate 256-bit key - Useful for programmatically generated keys or key derivation

Example:

var cryptoConfig = muxerFilter as IVFCryptoConfig;
if (cryptoConfig != null)
{
    // Generate random key
    byte[] keyData = new byte[32];
    using (var rng = new RNGCryptoServiceProvider())
    {
        rng.GetBytes(keyData);
    }

    // Apply binary key
    cryptoConfig.ApplyBinary(keyData);

    // Store keyData securely for later decryption
    SaveKeyToSecureStorage(keyData);
}

Filter CLSIDs¶

Encrypt Muxer Filter¶

Muxes video and audio streams into encrypted format. CLSID:

// {F1D3727A-88DE-49ab-A635-280BEFEFF902}
DEFINE_GUID(CLSID_EncryptMuxer,
    0xf1d3727a, 0x88de, 0x49ab, 0xa6, 0x35, 0x28, 0xb, 0xef, 0xef, 0xf9, 0x2);

Usage (C++):

IBaseFilter* pMuxer = nullptr;
hr = CoCreateInstance(
    CLSID_EncryptMuxer,
    NULL,
    CLSCTX_INPROC_SERVER,
    IID_IBaseFilter,
    (void**)&pMuxer
);

Usage (C#):

var muxerFilter = (IBaseFilter)Activator.CreateInstance(
    Type.GetTypeFromCLSID(new Guid("F1D3727A-88DE-49ab-A635-280BEFEFF902"))
);

Decrypt Demuxer Filter¶

Demuxes and decrypts encrypted files.

CLSID:

// {D2C761F0-9988-4f79-9B0E-FB2B79C65851}
DEFINE_GUID(CLSID_EncryptDemuxer,
    0xd2c761f0, 0x9988, 0x4f79, 0x9b, 0xe, 0xfb, 0x2b, 0x79, 0xc6, 0x58, 0x51);

Usage (C++):

IBaseFilter* pDemuxer = nullptr;
hr = CoCreateInstance(
    CLSID_EncryptDemuxer,
    NULL,
    CLSCTX_INPROC_SERVER,
    IID_IBaseFilter,
    (void**)&pDemuxer
);

Usage (C#):

var demuxerFilter = (IBaseFilter)Activator.CreateInstance(
    Type.GetTypeFromCLSID(new Guid("D2C761F0-9988-4f79-9B0E-FB2B79C65851"))
);

Video Encryption SDK - Interface Reference¶

Overview¶

IVFCryptoConfig Interface¶

Interface GUID¶

Inheritance¶

Inherits from IUnknown¶

Interface Definitions¶

C++ Definition¶

C# Definition¶

Delphi Definition¶

Methods¶

put_Provider¶

get_Provider¶

put_Password¶

HavePassword¶

IVFPasswordProvider Interface¶

Interface GUID¶

Inheritance¶

Inherits from IUnknown¶

Interface Definitions¶

C++ Definition¶

C# Definition¶

Methods¶

QueryPassword¶

C# Helper Methods¶

ApplyString¶

ApplyFile¶

ApplyBinary¶

Filter CLSIDs¶

Encrypt Muxer Filter¶

Decrypt Demuxer Filter¶

See Also¶

Inherits from `IUnknown`¶

Inherits from `IUnknown`¶