Example: Tdea.FileDecrypt  Tdea.FileEncrypt  (2)

[VB6 equivalent: TDEA_FileExt]

Dim abKey() As Byte
Dim abIV() As Byte
Dim strFilePlain As String
Dim strFileCipher As String
Dim strFileCheck As String
Dim strFileChk1 As String
Dim nRet As Integer

' Input file is exactly 19 bytes long
strFilePlain = "nowis19.txt"
strFileCipher = "nowis19.tdea.enc.dat"
strFileCheck = "nowis19.tdea.chk.txt"
strFileChk1 = "nowis19.tdea.chk1.txt"

' Create the key and IV as arrays of bytes
' This creates an array of 24 bytes {&H01, &H23, ... &H67}
abKey = Cnv.FromHex("0123456789ABCDEFFEDCBA987654321089ABCDEF01234567")
' This creates an array of 8 bytes {&H12, &H34, ... &HEF}
abIV = Cnv.FromHex("1234567890ABCDEF ")

' Encrypt plaintext file to ciphertext with embedded IV at beginning
' Output file = 32-byte ciphertext file .enc.dat
nRet = Tdea.FileEncrypt(strFileCipher, strFilePlain, abKey, Mode.CBC, abIV, CipherFileOption.PrefixIV)
Console.WriteLine("TDEA_FileExt(ENCRYPT) returns " & nRet)
Console.WriteLine("Output file '" & strFileCipher & "' is " & FileLen(strFileCipher) & " bytes")

' Now decrypt it back to original plaintext - this file should be 19 bytes long
nRet = Tdea.FileDecrypt(strFileCheck, strFileCipher, abKey, Mode.CBC, abIV, CipherFileOption.PrefixIV)
Console.WriteLine("TDEA_FileExt(DECRYPT) returns " & nRet)
Console.WriteLine("Output file '" & strFileCheck & "' is " & FileLen(strFileCheck) & " bytes")

' Alternatively, decrypt and leave padding bytes in place - this file should be 24 bytes long
nRet = Tdea.FileDecrypt(strFileChk1, strFileCipher, abKey, Mode.CBC, abIV, CipherFileOption.PrefixIV Or CipherFileOption.LeavePadding)
Console.WriteLine("TDEA_FileExt(DECRYPT, General.PAD_LEAVE) returns " & nRet)
Console.WriteLine("Output file '" & strFileChk1 & "' is " & FileLen(strFileChk1) & " bytes")

See Also:
Tdea.FileDecrypt Method (String, String, Byte[], Mode, Byte[], CipherFileOption)
Tdea.FileEncrypt Method (String, String, Byte[], Mode, Byte[], CipherFileOption)

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