AES128_BytesMode

CryptoSys API Library Manual

AES128_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 AES128_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 = AES128_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  AES128_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

Aes128.Encrypt Method (Byte[], Byte[], Mode, Byte[])
Aes128.Decrypt Method (Byte[], Byte[], Mode, Byte[])

Remarks

The input array lpData must be an exact multiple of 16 bytes long. If not, an error code will be returned. 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 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 = "C3153108A8DD340C0BCB1DFE8D25D2320EE0E66BD2BB4A313FB75C5638E9E177"
    abKey = cnvBytesFromHexStr("0123456789ABCDEFF0E1D2C3B4A59687")
    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 = AES128_BytesMode(abResult(0), abData(0), nDataLen, abKey(0), _
        ENCRYPT, "CBC", abInitV(0))
    Debug.Print "CT=" & cnvHexStrFromBytes(abResult)
    Debug.Print "OK=" & sCorrect

    ' Now decrypt back
    nRet = AES128_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=0123456789ABCDEFF0E1D2C3B4A59687
IV=FEDCBA9876543210FEDCBA9876543210
PT=4E6F77206973207468652074696D6520666F7220616C6C20676F6F64206D656E
CT=C3153108A8DD340C0BCB1DFE8D25D2320EE0E66BD2BB4A313FB75C5638E9E177
OK=C3153108A8DD340C0BCB1DFE8D25D2320EE0E66BD2BB4A313FB75C5638E9E177
P'=Now is the time for all good men