(Lianja) RSA Encrypt String to Encoded Result and Reverse

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

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// 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.
loPubKey = createobject("CkPublicKey")
// In all Chilkat methods expecting a path, you pass either absolute or relative paths.
llSuccess = loPubKey.LoadFromFile("rsaKeys/myTestRsaPublic.pem")
if (llSuccess = .F.) then
    ? loPubKey.LastErrorText
    release loPubKey
    return
endif

loRsa = createobject("CkRsa")

// Tell RSA to use the public key.
loRsa.ImportPublicKeyObj(loPubKey)

// 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.
loRsa.Charset = "utf-8"
loRsa.EncodingMode = "base64"

// Be Careful when Using non-us-ascii String Literals in Source Code
lcEncryptedB64 = loRsa.EncryptStringENC("Élève français dîne à côté d’un café où l’on sert déjà du gâteau au chocolat et des éclairs délicieux",.F.)

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

// Load the matching 2048-bit RSA private key.
loPrivKey = createobject("CkPrivateKey")
lcPassword = "secret"
llSuccess = loPrivKey.LoadAnyFormatFile("rsaKeys/myTestRsaPrivate.pem",lcPassword)
if (llSuccess = .F.) then
    ? loPrivKey.LastErrorText
    release loPubKey
    release loRsa
    release loPrivKey
    return
endif

// Tell the RSA object to use the private key.
loRsa.ImportPrivateKeyObj(loPrivKey)

// Indicate that after decrypting the resultant decrypted bytes contains the utf-8 byte representation of the text.
loRsa.Charset = "utf-8"
loRsa.EncodingMode = "base64"
lcOriginalText = loRsa.DecryptStringENC(lcEncryptedB64,.T.)
if (llSuccess = .F.) then
    ? loRsa.LastErrorText
    release loPubKey
    release loRsa
    release loPrivKey
    return
endif

? "Original text = " + lcOriginalText
? "Success."


release loPubKey
release loRsa
release loPrivKey