DecryptFileA function (winbase.h)

Article
02/22/2024

Decrypts an encrypted file or directory.

Syntax

BOOL DecryptFileA(
  [in] LPCSTR lpFileName,
       DWORD  dwReserved
);

Parameters

[in] lpFileName

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.

dwReserved

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.

Remarks

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.

Note

The winbase.h header defines DecryptFile as an alias which 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 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 [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)