Lua

Streaming Encryption by Encrypting in Chunks

See more Encryption Examples

Encrypt data in chunks. 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"
crypt.cipher_mode = "cbc"
crypt.key_length = 128

crypt:set_encoded_key("000102030405060708090A0B0C0D0E0F", "hex")
crypt:set_encoded_iv("000102030405060708090A0B0C0D0E0F", "hex")

crypt.encoding_mode = "hex"
local txt1 = "The quick brown fox jumped over the lazy dog.\r\n"
local txt2 = "-\r\n"
local txt3 = "Done.\r\n"

local sbEncrypted = chilkat.StringBuilder.new()

-- Encrypt the 1st chunk:
-- (don't worry about feeding the data to the encryptor in
-- exact multiples of the encryption algorithm's block size.
-- Chilkat will buffer the data.)
crypt.first_chunk = true
crypt.last_chunk = false
sbEncrypted:append(crypt:encrypt_string_enc(txt1))

-- Encrypt the 2nd chunk
crypt.first_chunk = false
crypt.last_chunk = false
sbEncrypted:append(crypt:encrypt_string_enc(txt2))

-- Now encrypt N more chunks...
-- Remember -- we're doing this in CBC mode, so each call
-- to the encrypt method depends on the state from previous
-- calls...
crypt.first_chunk = false
crypt.last_chunk = false
for i = 0, 4 do
    sbEncrypted:append(crypt:encrypt_string_enc(txt1))
    sbEncrypted:append(crypt:encrypt_string_enc(txt2))
end

-- Now encrypt the last chunk:
crypt.first_chunk = false
crypt.last_chunk = true
sbEncrypted:append(crypt:encrypt_string_enc(txt3))

print(sbEncrypted:get_as_string())

-- Now decrypt in one call.
-- (The data we're decrypting is both the first AND last chunk.)
crypt.first_chunk = true
crypt.last_chunk = true
local decryptedText = crypt:decrypt_string_enc(sbEncrypted:get_as_string())

print(decryptedText)

-- Note: You may decrypt in N chunks by setting the FirstChunk
-- and LastChunk properties prior to calling the Decrypt* methods.