(Lianja) Demonstrate RSA Encrypt/Decrypt using BinData

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

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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

// Create some binary data to encrypt.
loBd = createobject("CkBinData")
i = 0
for i = 0 to 49
    loBd.AppendByte(i)
next

// Show the bytes to be encrypted in hex format:
? "To be encrypted: " + loBd.GetEncoded("hex")

// To be encrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031

// RSA encrypt the contents of the bd, replacing the contents with the RSA encrypted data.
loRsa.EncryptBd(loBd,.F.)

// Now it is encrypted.
? "Encrypted size = " + str(loBd.NumBytes)
? loBd.GetEncoded("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.
loPrivKey = createobject("CkPrivateKey")
lcPassword = "secret"
llSuccess = loPrivKey.LoadAnyFormatFile("rsaKeys/myTestRsaPrivate.pem",lcPassword)
if (llSuccess = .F.) then
    ? loPrivKey.LastErrorText
    release loPubKey
    release loRsa
    release loBd
    release loPrivKey
    return
endif

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

// Decrypt
llSuccess = loRsa.DecryptBd(loBd,.T.)
if (llSuccess = .F.) then
    ? loRsa.LastErrorText
    release loPubKey
    release loRsa
    release loBd
    release loPrivKey
    return
endif

// Examine the contents of bd to see if it now contains the unencrypted original data.
? "Decrypted: " + loBd.GetEncoded("hex")

// Decrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031


release loPubKey
release loRsa
release loBd
release loPrivKey