DecryptFileA function

Decrypts an encrypted file or directory.


BOOL DecryptFileA(
  LPCSTR lpFileName,
  DWORD  dwReserved



The name of the file or directory to be decrypted.

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.


Reserved; must be zero.

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.


The DecryptFile function requires exclusive access to the file being decrypted, and will fail if another process is using the file. If the file is not encrypted, DecryptFile simply returns a nonzero value, which indicates success.

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 decrypted.

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.


Minimum supported client Windows XP [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

See also



File Encryption

File Management Functions