Tcl

AES Encrypt and Decrypt a File

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

load ./chilkat.dll

set success 0

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

set crypt [new_CkCrypt2]

CkCrypt2_put_CryptAlgorithm $crypt "aes"

# CipherMode may be "ecb" or "cbc"
CkCrypt2_put_CipherMode $crypt "cbc"

# KeyLength may be 128, 192, 256
CkCrypt2_put_KeyLength $crypt 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.
CkCrypt2_put_PaddingScheme $crypt 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.
set ivHex "000102030405060708090A0B0C0D0E0F"
CkCrypt2_SetEncodedIV $crypt $ivHex "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.
set keyHex "000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F"
CkCrypt2_SetEncodedKey $crypt $keyHex "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.
set inFile "/Users/chilkat/testData/pdf/sample.pdf"
set outFile "/Users/chilkat/testData/p7m/sample.pdf.aes"
set success [CkCrypt2_CkEncryptFile $crypt $inFile $outFile]
if {$success != 1} then {
    puts [CkCrypt2_lastErrorText $crypt]
    delete_CkCrypt2 $crypt
    exit
}

# For demonstration purposes, a different instance of the object will be used
# for decryption.
set decrypt [new_CkCrypt2]

# All settings must match to be able to decrypt:
CkCrypt2_put_CryptAlgorithm $decrypt "aes"
CkCrypt2_put_CipherMode $decrypt "cbc"
CkCrypt2_put_KeyLength $decrypt 256
CkCrypt2_put_PaddingScheme $decrypt 0
CkCrypt2_SetEncodedIV $decrypt $ivHex "hex"
CkCrypt2_SetEncodedKey $decrypt $keyHex "hex"

# Decrypt the .aes
set inFile "/Users/chilkat/testData/p7m/sample.pdf.aes"
set outFile "/Users/chilkat/testData/pdf/recovered.pdf"
set success [CkCrypt2_CkDecryptFile $decrypt $inFile $outFile]
if {$success == 0} then {
    puts [CkCrypt2_lastErrorText $decrypt]
    delete_CkCrypt2 $crypt
    delete_CkCrypt2 $decrypt
    exit
}

puts "Success!"

delete_CkCrypt2 $crypt
delete_CkCrypt2 $decrypt