AES128_Update

Carries out the AES transformation function on a byte array according to the direction and mode set up by an earlier call to AES128_Init() or AES128_InitHex().

VBA/VB6 Syntax

nRet = AES128_Update(hContext, abData(0), nDataLen)

C/C++ Syntax

Parameters

hContext

[in] handle to the AES context set up by an earlier call to AES128_Init() or AES128_InitHex().

lpData

[in,out] array containing the input to be processed by the AES function and to receive the output.

nDataLen

[in] containing length of the data in bytes.

Returns (VBA/C)

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

.NET Equivalent

Aes128.Update Method (Byte[])

Remarks

The input array lpData must be an exact multiple of 16 bytes long. If not, an error code will be returned. Note that the output overwrites the input.

Example

This example carries out the third (I=2) Monte Carlo MOVS test in ECB decrypt mode. (Ref: AES Candidate Algorithm Submissions, update 17 Feb 1998, file cbc_e_m.txt [RIJNVALS]).

    Dim nRet As Long
    Dim hContext As Long
    Dim abBlock() As Byte
    Dim abKey() As Byte
    Dim abCorrect() As Byte
    Dim j As Integer
    
' File: ecb_d_m.txt
' KEYSIZE=128 I=2
' KEY=A7BC3BD0EABD9EBA981E23E6FFC9C9C2
' CT=E3FD51123B48A2E2AB1DB29894202222
' PT=877B88A77AEF04F05546539E17259F53
     ' Convert to Byte format
    abKey = cnvBytesFromHexStr("A7BC3BD0EABD9EBA981E23E6FFC9C9C2")
    abBlock = cnvBytesFromHexStr("E3FD51123B48A2E2AB1DB29894202222")
    abCorrect = cnvBytesFromHexStr("877B88A77AEF04F05546539E17259F53")
    
    Debug.Print "AES Monte Carlo ECB Mode Decrypt:"
    Debug.Print "KY=" & cnvHexStrFromBytes(abKey)
    Debug.Print "CT=" & cnvHexStrFromBytes(abBlock)
    
    hContext = AES128_Init(abKey(0), DECRYPT, "ECB", 0)
    If hContext = 0 Then
        MsgBox "Failed to set context", vbCritical
        Exit Function
    End If
    ' Do 10,000 times
    For j = 0 To 9999
        nRet = AES128_Update(hContext, abBlock(0), 16)
    Next
    Debug.Print "PT=" & cnvHexStrFromBytes(abBlock)
    Debug.Print "OK=" & cnvHexStrFromBytes(abCorrect)
    nRet = AES128_Final(hContext)
    
    Debug.Assert (StrConv(abCorrect, vbUnicode) = StrConv(abBlock, vbUnicode))

This should result in output as follows:

AES Monte Carlo ECB Mode Decrypt:
KY=A7BC3BD0EABD9EBA981E23E6FFC9C9C2
CT=E3FD51123B48A2E2AB1DB29894202222
PT=877B88A77AEF04F05546539E17259F53
OK=877B88A77AEF04F05546539E17259F53

See Also

AES128_Init AES128_InitHex AES128_UpdateHex AES128_Final

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