TDEA_File

Encrypts or decrypts a file using a specified mode. The key and initialization vector are passed as arrays of bytes. PKCS-5/7 padding is used.

VBA/VB6 Syntax


Public Declare Function TDEA_File Lib "diCrPKI.dll" 
(ByVal strFileOut As String, ByVal strFileIn As String, ByRef lpKey As Byte, 
ByVal fEncrypt As Long, ByVal strMode As String, ByRef lpInitV As Byte) As Long


nRet = TDEA_File(strFileOut, strFileIn, lpKey(0), fEncrypt, strMode, lpInitV(0))

C/C++ Syntax


long __stdcall TDEA_File(const char *szFileOut, const char *szFileIn, const unsigned char *lpKey, long fEncrypt, const char *szMode, const unsigned char *lpIV);

Parameters

szFileOut

[in] with the full path name of the output file to be created.

szFileIn

[in] with the full path name of the input file to be processed.

lpKey

[in] array containing the key.

fEncrypt

[in] direction flag: set as ENCRYPT (True) to encrypt or DECRYPT (False) to decrypt.

szMode

[in] specifying the confidentiality mode:
"ECB" for Electronic Codebook mode,
"CBC" for Cipher Block Chaining mode,
"CFB" for 64-bit Cipher Feedback mode,
"OFB" for Output Feedback mode, or
"CTR" for Counter mode.

lpIV

[in] array containing the initialization vector (IV), or zero (0) for ECB mode.

Returns (VBA/C)

If successful, the return value is zero; otherwise it returns a nonzero error code.

.NET Equivalent

Tdea.FileEncrypt Method (String, String, Byte[], Mode, Byte[])
Tdea.FileDecrypt Method (String, String, Byte[], Mode, Byte[])

Remarks

The key array abKey() must be exactly 16 bytes long. The initialization vector abInitV() must be exactly the block size of 16 bytes long, except for ECB mode, where it is ignored (use 0). The output file szFileOut will be overwritten without warning. If there is an error, the output file will not exist. The input and output files must not be the same. In ECB and CBC modes, a padding string will be added or assumed according to the method outlined in Section 6.3 of [CMS], which is the same as the padding method in [PKCS7] section 10.3 and [PKCS5] section 6.1.1 and [RFC1423] para 1.1.

Example

Const MY_PATH As String = "" Dim aKey() As Byte Dim strFileOut As String Dim strFileIn As String Dim strFileChk As String Dim nRet As Long ' Construct full path names to files strFileIn = MY_PATH & "hello.txt" strFileOut = MY_PATH & "hello.tdea.enc.dat" strFileChk = MY_PATH & "hello.tdea.chk.txt" ' Create the key as an array of bytes ' This creates an array of 24 bytes {&HFE, &HDC, ... &H10} aKey = cnvBytesFromHexStr("fedcba9876543210fedcba9876543210fedcba9876543210") ' Encrypt plaintext file to ciphertext ' Output file = 16-byte ciphertext file hello.enc nRet = TDEA_File(strFileOut, strFileIn, aKey(0), ENCRYPT, "ECB", 0) Debug.Print nRet ' Now decrypt it nRet = TDEA_File(strFileChk, strFileOut, aKey(0), DECRYPT, "ECB", 0) Debug.Print nRet