B4X 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. 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

'  Encrypt the utf-8 byte representation of the string.
rsa.Charset = "utf-8"
rsa.EncodingMode = "base64"

'  Be Careful when Using non-us-ascii String Literals in Source Code
Dim encryptedB64 As String = rsa.EncryptStringENC("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.
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)

'  Indicate that after decrypting the resultant decrypted bytes contains the utf-8 byte representation of the text.
rsa.Charset = "utf-8"
rsa.EncodingMode = "base64"
Dim originalText As String = rsa.DecryptStringENC(encryptedB64, True)
If success = False Then
    Log(rsa.LastErrorText)
    Return
End If


Log("Original text = " & originalText)
Log("Success.")