(CkPython) AES Encrypt and Decrypt a File

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

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import sys
import chilkat

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

crypt = chilkat.CkCrypt2()

crypt.put_CryptAlgorithm("aes")

# CipherMode may be "ecb" or "cbc"
crypt.put_CipherMode("cbc")

# KeyLength may be 128, 192, 256
crypt.put_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.
crypt.put_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.
ivHex = "000102030405060708090A0B0C0D0E0F"
crypt.SetEncodedIV(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.
keyHex = "000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F"
crypt.SetEncodedKey(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.
inFile = "/Users/chilkat/testData/pdf/sample.pdf"
outFile = "/Users/chilkat/testData/p7m/sample.pdf.aes"
success = crypt.CkEncryptFile(inFile,outFile)
if (success != True):
    print(crypt.lastErrorText())
    sys.exit()

# For demonstration purposes, a different instance of the object will be used
# for decryption.
decrypt = chilkat.CkCrypt2()

# All settings must match to be able to decrypt:
decrypt.put_CryptAlgorithm("aes")
decrypt.put_CipherMode("cbc")
decrypt.put_KeyLength(256)
decrypt.put_PaddingScheme(0)
decrypt.SetEncodedIV(ivHex,"hex")
decrypt.SetEncodedKey(keyHex,"hex")

# Decrypt the .aes
inFile = "/Users/chilkat/testData/p7m/sample.pdf.aes"
outFile = "/Users/chilkat/testData/pdf/recovered.pdf"
success = decrypt.CkDecryptFile(inFile,outFile)
if (success == False):
    print(decrypt.lastErrorText())
    sys.exit()

print("Success!")