(Lianja) AES Encrypt and Decrypt a File

Lianja demonstrates how to AES encrypt a file of any size, and then decrypt.

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// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

loCrypt = createobject("CkCrypt2")

loCrypt.CryptAlgorithm = "aes"

// CipherMode may be "ecb" or "cbc"
loCrypt.CipherMode = "cbc"

// KeyLength may be 128, 192, 256
loCrypt.KeyLength = 256

// The padding scheme determines the contents of the bytes
// that are added to pad the result to a multiple of the
// encryption algorithm's block size.  AES has a block
// size of 16 bytes, so encrypted output is always
// a multiple of 16.
loCrypt.PaddingScheme = 0

// An initialization vector is required if using CBC mode.
// ECB mode does not use an IV.
// The length of the IV is equal to the algorithm's block size.
// It is NOT equal to the length of the key.
lcIvHex = "000102030405060708090A0B0C0D0E0F"
loCrypt.SetEncodedIV(lcIvHex,"hex")

// The secret key must equal the size of the key.  For
// 256-bit encryption, the binary secret key is 32 bytes.
// For 128-bit encryption, the binary secret key is 16 bytes.
lcKeyHex = "000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F"
loCrypt.SetEncodedKey(lcKeyHex,"hex")

// Encrypt a file, producing the .aes as output.
// The input file is unchanged, the output .aes contains the encrypted
// contents of the input file.

// Note: The .aes output file has no file format.  It is simply a stream
// of bytes that resembles random binary data.
lcInFile = "/Users/chilkat/testData/pdf/sample.pdf"
lcOutFile = "/Users/chilkat/testData/p7m/sample.pdf.aes"
llSuccess = loCrypt.CkEncryptFile(lcInFile,lcOutFile)
if (llSuccess <> .T.) then
    ? loCrypt.LastErrorText
    release loCrypt
    return
endif

// For demonstration purposes, a different instance of the object will be used
// for decryption.
loDecrypt = createobject("CkCrypt2")

// All settings must match to be able to decrypt:
loDecrypt.CryptAlgorithm = "aes"
loDecrypt.CipherMode = "cbc"
loDecrypt.KeyLength = 256
loDecrypt.PaddingScheme = 0
loDecrypt.SetEncodedIV(lcIvHex,"hex")
loDecrypt.SetEncodedKey(lcKeyHex,"hex")

// Decrypt the .aes
lcInFile = "/Users/chilkat/testData/p7m/sample.pdf.aes"
lcOutFile = "/Users/chilkat/testData/pdf/recovered.pdf"
llSuccess = loDecrypt.CkDecryptFile(lcInFile,lcOutFile)
if (llSuccess = .F.) then
    ? loDecrypt.LastErrorText
    release loCrypt
    release loDecrypt
    return
endif

? "Success!"


release loCrypt
release loDecrypt