(Visual Basic 6.0) RSA Encrypt and Decrypt Credit Card Numbers

Visual Basic 6.0 sample code to RSA public-key encrypt and decrypt credit card numbers. The RSA key is loaded from an unencrypted PKCS8 file. Chilkat provides many ways of setting the key -- loading from both encrypted and unencrypted PEM, PKCS8, DER, PVK, etc. Keys may be loaded from files or in-memory representations. (The RSA component also provides the ability to generate RSA keys.)

Note: This example requires Chilkat v11.0.0 or greater.

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Dim success As Long
success = 0

' This example assumes the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim rsa As New ChilkatRsa

Dim privKey As New PrivateKey

' Load an RSA private key from a file:
success = privKey.LoadAnyFormatFile("rsaPrivateKey.key","")
If (success = 0) Then
    Debug.Print privKey.LastErrorText
    Exit Sub
End If

' Get the public part of the private key.
Dim pubKey As New PublicKey
success = privKey.ToPublicKey(pubKey)

success = rsa.UsePublicKey(pubKey)
If (success = 0) Then
    Debug.Print rsa.LastErrorText
    Exit Sub
End If

' Encrypt a VISA credit card number:
' 1234-5678-0000-9999
Dim ccNumber As String
ccNumber = "1234567800009999"

Dim usePrivateKey As Long
usePrivateKey = 0
rsa.EncodingMode = "base64"
Dim encryptedStr As String
encryptedStr = rsa.EncryptStringENC(ccNumber,usePrivateKey)
Debug.Print "Encrypted:"
Debug.Print encryptedStr

' Now decrypt:
Dim rsaDecryptor As New ChilkatRsa

rsaDecryptor.EncodingMode = "base64"
success = rsaDecryptor.UsePrivateKey(privKey)

usePrivateKey = 1
Dim decryptedStr As String
decryptedStr = rsaDecryptor.DecryptStringENC(encryptedStr,usePrivateKey)

Debug.Print "Decrypted:"
Debug.Print decryptedStr

' Important: RSA encryption should only be used to encrypt small amounts of data.
' It is typically used for encrypting symmetric encryption
' keys such that a symmetric encryption algorithm, such as 
' AES is then used to encrypt/decrypt bulk data