Lua Requires Chilkat v11.0.0+

Demonstrate RSA Encrypt/Decrypt using BinData

See more RSA Examples

Demonstrates how to RSA encrypt and decrypt data contained in a Chilkat BinData object. Lua

local chilkat = require("chilkat")

-- The RSA public key is used for encryption, and the private key for decryption.

-- The public key's role is to make encryption accessible to anyone while ensuring that
-- only the private key holder can decrypt the messages.
-- The public key is designed to be widely distributed so anyone can use it to encrypt messages
-- intended for the owner of the private key.

-- Load our 2048-bit RSA public key.
local pubKey = chilkat.PublicKey.new()
-- In all Chilkat methods expecting a path, you pass either absolute or relative paths.
local success = pubKey:load_from_file("rsaKeys/myTestRsaPublic.pem")
if not success then
    print(pubKey.last_error_text)
    return
end

local rsa = chilkat.Rsa.new()

-- Tell RSA to use the public key.
rsa:use_public_key(pubKey)

-- RSA encryption is for small amounts of data, on the order of 200 bytes or less.
-- The maximum number of bytes that can be RSA encrypted depends
-- on the RSA key size and padding scheme (OAEP padding vs PKCS#1 v1.5 padding).
-- For specific limits, see: RSA Encryption Maximum Number of Bytes

-- Create some binary data to encrypt.
local bd = chilkat.BinData.new()
for i = 0, 49 do
    bd:append_byte(i)
end

-- Show the bytes to be encrypted in hex format:
print("To be encrypted: " .. bd:get_encoded("hex"))

-- To be encrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031

-- RSA encrypt the contents of the bd, replacing the contents with the RSA encrypted data.
rsa:encrypt_bd(bd, false)

-- Now it is encrypted.
print("Encrypted size = " .. bd.num_bytes)
print(bd:get_encoded("hex"))

-- Encrypted size = 256
-- 749ED9D0A8767C06C09AD9697F654F86B145F966722F9714902C4175BDBD02E68984ECF111D4D461
-- EDB4A8E677D399D19CCA60F35C6DE9972F4262880FE9D77DB75915393E8E7DB80AAB5E383013FAEB
-- 60C77D1E6FECC9A7C8426976416C6218FE7DA998EE063CE709E79C240F8625F4A56A0A33AFD63F7A
-- BA26F2A692B42E878C53B78602C725FE63FF961A46A2B9D436E5E3D9D64AE3F1D1F5AD5F5B47FCD69
-- 447306B77F2FD6D766CCAA1A110A3371586B43DF0D7FFE2220D1B305CF9371AC342F849FB0C90CD99E
-- C176928D877FE1C0DE1A7CB6EB824FEC7E1DCF90EF2C6BA9F1DFD3EBFBE89C51AF074DC6AE02E544A78
-- 5018C36D3D48B2EF5202AF61AC

-- ------------------------------------------------------------------------------------------------------------------------
-- Let's decrypt, which requires the matching private key...

-- Load the matching 2048-bit RSA private key.
local privKey = chilkat.PrivateKey.new()
local password = "secret"
success = privKey:load_any_format_file("rsaKeys/myTestRsaPrivate.pem", password)
if not success then
    print(privKey.last_error_text)
    return
end

-- Tell the RSA object to use the private key.
rsa:use_private_key(privKey)

-- Decrypt
success = rsa:decrypt_bd(bd, true)
if not success then
    print(rsa.last_error_text)
    return
end

-- Examine the contents of bd to see if it now contains the unencrypted original data.
print("Decrypted: " .. bd:get_encoded("hex"))

-- Decrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031