Lua

AES Encrypt and Decrypt a File

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

local chilkat = require("chilkat")

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

local crypt = chilkat.Crypt2.new()

crypt.crypt_algorithm = "aes"

-- CipherMode may be "ecb" or "cbc"
crypt.cipher_mode = "cbc"

-- KeyLength may be 128, 192, 256
crypt.key_length = 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.padding_scheme = 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.
local ivHex = "000102030405060708090A0B0C0D0E0F"
crypt:set_encoded_iv(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.
local keyHex = "000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F"
crypt:set_encoded_key(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.
local inFile = "/Users/chilkat/testData/pdf/sample.pdf"
local outFile = "/Users/chilkat/testData/p7m/sample.pdf.aes"
local success = crypt:ck_encrypt_file(inFile, outFile)
if not success then
    print(crypt.last_error_text)
    return
end

-- For demonstration purposes, a different instance of the object will be used
-- for decryption.
local decrypt = chilkat.Crypt2.new()

-- All settings must match to be able to decrypt:
decrypt.crypt_algorithm = "aes"
decrypt.cipher_mode = "cbc"
decrypt.key_length = 256
decrypt.padding_scheme = 0
decrypt:set_encoded_iv(ivHex, "hex")
decrypt:set_encoded_key(keyHex, "hex")

-- Decrypt the .aes
inFile = "/Users/chilkat/testData/p7m/sample.pdf.aes"
outFile = "/Users/chilkat/testData/pdf/recovered.pdf"
success = decrypt:ck_decrypt_file(inFile, outFile)
if not success then
    print(decrypt.last_error_text)
    return
end

print("Success!")