TDEA_HexMode

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

VBA/VB6 Syntax

nRet = TDEA_HexMode(strOutput, strInput, strKey, fEncrypt, strMode, strIV)

C/C++ Syntax

Parameters

szOutput

[out] of sufficient length to receive the output.

szInput

[in] containing the input data in hex format.

szKey

[in] containing the key in hex format.

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 hex format.

Returns (VBA/C)

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

.NET Equivalent

Tdea.Encrypt Method (String, String, Mode, String)
Tdea.Decrypt Method (String, String, Mode, String)

Remarks

For ECB and CBC modes, the length of the input string szInput must be a multiple of 16 hex characters long (i.e. representing a multiple of 8 bytes) otherwise an error will result. The key string szKey must be exactly 48 hex characters long (i.e. representing exactly 24 bytes/192 bits). The initialization vector string szIV must be exactly 16 hex characters long (i.e. representing exactly the block size of 8 bytes) unless szMode is ECB, in which case szIV is ignored (use ""). Valid hexadecimal characters are [0-9A-Fa-f]. The output string szOutput must be set up with the same number of characters as the input string before calling. The variables szOutput and szInput should be different.

Example

This example is from Section 8.1 of [SMIME-EX].

Dim nRet As Long
Dim sOutput As String
Dim sInput As String
Dim sKey As String
Dim sInitV As String
Dim sCorrect As String

sInput = "5468697320736F6D652073616D706520636F6E74656E742E0808080808080808"
'         T h i s _ s o m e _ s a m p e _ c o n t e n t . (padding 8 x 08)
sKey = "737C791F25EAD0E04629254352F7DC6291E5CB26917ADA32"
sInitV = "B36B6BFB6231084E"
sCorrect = "d76fd1178fbd02f84231f5c1d2a2f74a4159482964f675248254223daf9af8e4"
' Set sOutput to be same length as sInput
sOutput = String(Len(sInput), " ")

Debug.Print "KY=" & sKey
Debug.Print "PT=" & sInput
nRet = TDEA_HexMode(sOutput, sInput, sKey, ENCRYPT, "CBC", sInitV)
Debug.Print "CT=" & sOutput & nRet
Debug.Print "OK=" & sCorrect

sInput = sOutput
nRet = TDEA_HexMode(sOutput, sInput, sKey, DECRYPT, "CBC", sInitV)
Debug.Print "P'=" & sOutput & nRet

This should result in output as follows:

KY=737C791F25EAD0E04629254352F7DC6291E5CB26917ADA32
PT=5468697320736F6D652073616D706520636F6E74656E742E0808080808080808
CT=D76FD1178FBD02F84231F5C1D2A2F74A4159482964F675248254223DAF9AF8E4 0
OK=d76fd1178fbd02f84231f5c1d2a2f74a4159482964f675248254223daf9af8e4
P'=5468697320736F6D652073616D706520636F6E74656E742E0808080808080808 0

See Also

TDEA_BytesMode TDEA_B64Mode

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