AES256_BytesMode

CryptoSys API Library Manual

AES256_BytesMode

Encrypts or decrypts an array of Bytes using a specified mode. The key and IV data are in byte arrays.

VBA/VB6 Syntax


Public Declare Function AES256_BytesMode Lib "diCryptoSys.dll" 
	(ByRef lpOutput As Byte, ByRef lpData As Byte, ByVal nDataLen As Long, ByRef lpKey As Byte, 
	ByVal bEncrypt As Boolean, 
	ByVal strMode As String, ByRef lpInitV As Byte) As Long

nRet = AES256_Bytes(lpOutput(0), abData(0), nDataLen, abKey(0), bEncrypt, strMode, abInitV(0)) ' Note the "(0)" after the byte array parameters

C/C++ Syntax


long __stdcall  AES256_BytesMode(unsigned char *lpOutput, const unsigned char *lpInput, long nBytes, const unsigned char *lpKey, int fEncrypt, const char *szMode, const unsigned char *lpIV);

Parameters

lpOutput: [out] array of sufficient length to receive the output.
lpInput: [in] array containing the input data.
nBytes: [in] equal to length of the input data in bytes.
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 128-bit Cipher Feedback mode,
"OFB" for Output Feedback mode, or
"CTR" for Counter mode.
lpIV: [in] containing the initialization vector (IV), or zero (0) for ECB mode.

Returns (VBA/C)

If successful, the return value is 0; otherwise it returns a non-zero error code.

.NET Equivalent

Aes256.Encrypt Method (Byte[], Byte[], Mode, Byte[])
Aes256.Decrypt Method (Byte[], Byte[], Mode, Byte[])

Remarks

The input array lpData must be a multiple of the block size of 16 bytes long. If not, an error code will be returned. The key array abKey() must be exactly 32 bytes long (i.e. 256 bits). 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 array lpOutput must be at least as long as the input array. lpOutput and lpData may be the same.

Example

    Dim nRet As Long
    Dim strOutput As String
    Dim strInput As String
    Dim sCorrect As String
    Dim abKey()  As Byte
    Dim abInitV() As Byte
    Dim abResult() As Byte
    Dim abData() As Byte
    Dim nDataLen As Long

    ' Set up input in byte arrays
    strInput = "Now is the time for all good men"
    sCorrect = "36161E5B4B62401A5B57996F7D6839D34E181930DEBBAEBE84AE01139E9581A6"
    abKey = _
    cnvBytesFromHexStr("000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f")
    abInitV = cnvBytesFromHexStr("FEDCBA9876543210FEDCBA9876543210")
    abData = StrConv(strInput, vbFromUnicode)
    nDataLen = UBound(abData) - LBound(abData) + 1
    
    ' Pre-dimension output array
    ReDim abResult(nDataLen - 1)
    
    Debug.Print "KY=" & cnvHexStrFromBytes(abKey)
    Debug.Print "IV=" & cnvHexStrFromBytes(abInitV)
    Debug.Print "PT=" & cnvHexStrFromBytes(abData)
    ' Encrypt in one-off process
    nRet = AES256_BytesMode(abResult(0), abData(0), nDataLen, abKey(0), _
        ENCRYPT, "CBC", abInitV(0))
    Debug.Print "CT=" & cnvHexStrFromBytes(abResult)
    Debug.Print "OK=" & sCorrect
    Debug.Assert (sCorrect = cnvHexStrFromBytes(abResult))

    ' Now decrypt back
    nRet = AES256_BytesMode(abData(0), abResult(0), nDataLen, abKey(0), _
        DECRYPT, "CBC", abInitV(0))
    strOutput = StrConv(abData(), vbUnicode)
    Debug.Print "P'=" & strOutput
    
    ' Check
    Debug.Assert (strOutput = strInput)

This should result in output as follows:

KY=000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F
IV=FEDCBA9876543210FEDCBA9876543210
PT=4E6F77206973207468652074696D6520666F7220616C6C20676F6F64206D656E
CT=36161E5B4B62401A5B57996F7D6839D34E181930DEBBAEBE84AE01139E9581A6
OK=36161E5B4B62401A5B57996F7D6839D34E181930DEBBAEBE84AE01139E9581A6
P'=Now is the time for all good men