Lua Requires Chilkat v11.0.0+

RSA Encrypt String to Encoded Result and Reverse

See more RSA Examples

Demonstrates how to RSA encrypt a string to a base64 encoded result, and the reverse. 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

-- Encrypt the utf-8 byte representation of the string.
rsa.charset = "utf-8"
rsa.encoding_mode = "base64"

-- Be Careful when Using non-us-ascii String Literals in Source Code
local encryptedB64 = rsa:encrypt_string_enc("Élève français dîne à côté d’un café où l’on sert déjà du gâteau au chocolat et des éclairs délicieux", false)

-- ------------------------------------------------------------------------------------------------------------------------
-- 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)

-- Indicate that after decrypting the resultant decrypted bytes contains the utf-8 byte representation of the text.
rsa.charset = "utf-8"
rsa.encoding_mode = "base64"
local originalText = rsa:decrypt_string_enc(encryptedB64, true)
if not success then
    print(rsa.last_error_text)
    return
end

print("Original text = " .. originalText)
print("Success.")