DES_B64Mode

Encrypts or decrypts data represented as a base64 string using a specified mode. The key and initialization vector are represented as base64 strings.

VBA/VB6 Syntax

nRet = DES_B64Mode(strOutput, strInput, strKey, bEncrypt, strMode, strIV)

C/C++ Syntax

Parameters

szOutput

[out] of sufficient length to receive the output.

szInput

[in] containing the input data in base64.

szKey

[in] containing the key in base64.

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.

szIV

[in] containing the initialization vector (IV), if required, in base64.

Returns (VBA/C)

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

.NET Equivalent

Des.Encrypt Method (String, String, Mode, String, EncodingBase)
Des.Decrypt Method (String, String, Mode, String, EncodingBase)

Remarks

The length of the input string szInput must represent a multiple of the block size (8 bytes) when decoded. If not, an error will be returned. The initialization vector string szIV must represent exactly 8 bytes unless szMode is ECB, in which case szIV is ignored (use ""). The key szKey must also represent exactly 8 bytes, the required key length. The output string szOutput must be set up with at least the same number of characters as the input string before calling. The variables szOutput and szInput should be different.

Example

Dim nRet As Long
Dim strOutput As String
Dim strInput As String
Dim strKey As String
Dim strIV As String
Dim sCorrect As String

' Key:        "0123456789abcdef"
' IV:         "1234567890abcdef"
' Plaintext:  "Now is the time for all "
'             "4e6f77206973207468652074696d6520666f7220616c6c20"
' Ciphertext: "e5c7cdde872bf27c43e934008c389c0f683788499a7c05f6"
strInput = "Tm93IGlzIHRoZSB0aW1lIGZvciBhbGwg"
strKey = "ASNFZ4mrze8="
strIV = "EjRWeJCrze8="
sCorrect = "5cfN3ocr8nxD6TQAjDicD2g3iEmafAX2"

' Set strOutput to be same length as strInput
strOutput = String(Len(strInput), " ")

Debug.Print "KY=" & strKey
Debug.Print "IV=" & strIV
Debug.Print "PT=" & strInput
' Encrypt in one-off process
nRet = DES_B64Mode(strOutput, strInput, strKey, True, "CBC", strIV)
Debug.Print "CT=" & strOutput
Debug.Print "OK=" & sCorrect

' Now decrypt back to plain text
strInput = strOutput
nRet = DES_B64Mode(strOutput, strInput, strKey, DECRYPT, "CBC", strIV)
Debug.Print "P'=" & strOutput

This should result in output as follows:

KY=ASNFZ4mrze8=
IV=EjRWeJCrze8=
PT=Tm93IGlzIHRoZSB0aW1lIGZvciBhbGwg
CT=5cfN3ocr8nxD6TQAjDicD2g3iEmafAX2
OK=5cfN3ocr8nxD6TQAjDicD2g3iEmafAX2
P'=Tm93IGlzIHRoZSB0aW1lIGZvciBhbGwg

See Also

DES_HexMode DES_BytesMode

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