EncryptFileA function (winbase.h)
Encrypts a file or directory. All data streams in a file are encrypted. All new files created in an encrypted directory are encrypted.
Syntax
BOOL EncryptFileA(
[in] LPCSTR lpFileName
);
Parameters
[in] lpFileName
The name of the file or directory to be encrypted.
The caller must have the FILE_READ_DATA, FILE_WRITE_DATA, FILE_READ_ATTRIBUTES, FILE_WRITE_ATTRIBUTES, and SYNCHRONIZE access rights. For more information, see File Security and Access Rights.
Return value
If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero. To get extended error information, call GetLastError.
Remarks
The EncryptFile function requires exclusive access to the file being encrypted, and will fail if another process is using the file.
If the file is already encrypted, EncryptFile simply returns a nonzero value, which indicates success. If the file is compressed, EncryptFile will decompress the file before encrypting it.
If lpFileName specifies a read-only file, the function fails and GetLastError returns ERROR_FILE_READ_ONLY. If lpFileName specifies a directory that contains a read-only file, the functions succeeds but the directory is not encrypted.
To decrypt an encrypted file, use the DecryptFile function.
In Windows 8, Windows Server 2012, and later, this function is supported by the following technologies.
| Technology | Supported |
|---|---|
| Server Message Block (SMB) 3.0 protocol | Yes |
| SMB 3.0 Transparent Failover (TFO) | No |
| SMB 3.0 with Scale-out File Shares (SO) | No |
| Cluster Shared Volume File System (CsvFS) | No |
| Resilient File System (ReFS) | No |
SMB 3.0 does not support EFS on shares with continuous availability capability.
Note
The winbase.h header defines EncryptFile as an alias that automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that is not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows XP Professional [desktop apps only] |
| Minimum supported server | Windows Server 2003 [desktop apps only] |
| Target Platform | Windows |
| Header | winbase.h (include Windows.h) |
| Library | Advapi32.lib |
| DLL | Advapi32.dll |
| API set | ext-ms-win-advapi32-encryptedfile-l1-1-0 (introduced in Windows 8) |