MAC_AddBytes

Adds an array of bytes to be authenticated in the MAC context.

VBA/VB6 Syntax

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

C/C++ Syntax

Parameters

hContext

[in] Handle to the MAC context.

lpData

[in] Byte array containing the next part of the message.

nDataLen

[in] Number of bytes in the array

Returns (VBA/C)

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

VBA Wrapper Syntax

.NET Equivalent

Mac.AddData Method (Byte[])
Mac.AddData Method (String)

C++ (STL) Equivalent

Remarks

The handle hContext to the context must have been set up with a prior call to MAC_Init. The MAC_AddBytes function may be called many times before creating the final message digest with MAC_Final.

VBA users can use the more convenient wrapper functions macAddBytes and macAddString.

Example (VBA core function)

Example (VBA wrapper function)

' Test case 4 from RFC 2202 and RFC 4231
' key =           0x0102030405060708090a0b0c0d0e0f10111213141516171819
' key_len         25
' data =          0xcd repeated 50 times
' data_len =      50
Dim hContext As Long
Dim r As Long
Dim lpKey() As Byte
Dim lpMsg10() As Byte
Dim lpDigest() As Byte
Dim i As Long
lpKey = cnvBytesFromHexStr("0102030405060708090a0b0c0d0e0f10111213141516171819")
lpMsg10 = cnvBytesFromHexStr("cdcdcdcdcdcdcdcdcdcd")    ' 0xcd repeated 10 times

' HMAC-SHA-1
hContext = macInit(lpKey, API_HMAC_SHA1)
Debug.Print "macInit returns 0x" & Hex(hContext) & " (expected nonzero)"
For i = 1 To 5
    r = macAddBytes(hContext, lpMsg10)
    Debug.Print "macAddBytes returns " & r
Next
lpDigest = macFinal(hContext)
Debug.Print "MAC=" & cnvHexStrFromBytes(lpDigest)
Debug.Print "OK= " & "4c9007f4026250c6bc8414f9bf50c86c2d7235da"

' HMAC-SHA-256
hContext = macInit(lpKey, API_HMAC_SHA256)
Debug.Print "macInit returns 0x" & Hex(hContext) & " (expected nonzero)"
For i = 1 To 5
    r = macAddBytes(hContext, lpMsg10)
    'Debug.Print "macAddBytes returns " & r
Next
lpDigest = macFinal(hContext)
Debug.Print "MAC=" & cnvHexStrFromBytes(lpDigest)
Debug.Print "OK= " & "82558a389a443c0ea4cc819899f2083a85f0faa3e578f8077a2e3ff46729665b"

Dim strData As String
Dim strKey As String
' Test case 2 from RFC 2202 and RFC 4231
strData = "what do ya want for nothing?"
strKey = "Jefe"
lpKey = StrConv(strKey, vbFromUnicode)
hContext = macInit(lpKey, API_HMAC_SHA512)
' Split input into parts
r = macAddString(hContext, "what do ya")
r = macAddString(hContext, " want for ")
r = macAddString(hContext, "nothing?")
lpDigest = macFinal(hContext)
Debug.Print "MAC=" & cnvHexStrFromBytes(lpDigest)
Debug.Print "OK =" _
& "164b7a7bfcf819e2e395fbe73b56e0a387bd64222e831fd610270cd7ea250554" _
& "9758bf75c05a994a6d034f65f8f0e6fdcaeab1a34d4a6b4b636e070a38bce737" 

See Also

MAC_Init MAC_Final

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