B4X 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. B4X

Dim success As Boolean = False

'  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.
Dim pubKey As ChilkatPublicKey
pubKey.Initialize
'  In all Chilkat methods expecting a path, you pass either absolute or relative paths.
success = pubKey.LoadFromFile("rsaKeys/myTestRsaPublic.pem")
If success = False Then
    Log(pubKey.LastErrorText)
    Return
End If


Dim rsa As ChilkatRsa
rsa.Initialize

'  Tell RSA to use the public key.
rsa.UsePublicKey(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.
Dim bd As ChilkatBinData
bd.Initialize
Dim i As Int = 0
For i = 0 To 49
    bd.AppendByte(i)
Next

'  Show the bytes to be encrypted in hex format:
Log("To be encrypted: " & bd.GetEncoded("hex"))

'  To be encrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031

'  RSA encrypt the contents of the bd, replacing the contents with the RSA encrypted data.
rsa.EncryptBd(bd, False)

'  Now it is encrypted.
Log("Encrypted size = " & bd.NumBytes)
Log(bd.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.
Dim privKey As ChilkatPrivateKey
privKey.Initialize("privKey")
Dim password As String = "secret"
success = privKey.LoadAnyFormatFile("rsaKeys/myTestRsaPrivate.pem", password)
If success = False Then
    Log(privKey.LastErrorText)
    Return
End If


'  Tell the RSA object to use the private key.
rsa.UsePrivateKey(privKey)

'  Decrypt
success = rsa.DecryptBd(bd, True)
If success = False Then
    Log(rsa.LastErrorText)
    Return
End If


'  Examine the contents of bd to see if it now contains the unencrypted original data.
Log("Decrypted: " & bd.GetEncoded("hex"))

'  Decrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031