(Visual FoxPro) RSA Encrypt and Decrypt Credit Card Numbers

Visual FoxPro 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.)

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL loRsa
LOCAL loKey
LOCAL lnSuccess
LOCAL lcKeyXml
LOCAL lcCcNumber
LOCAL lnUsePrivateKey
LOCAL lcEncryptedStr
LOCAL loRsaDecryptor
LOCAL lcDecryptedStr

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

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Rsa')
loRsa = CreateObject('Chilkat.Rsa')

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.PrivateKey')
loKey = CreateObject('Chilkat.PrivateKey')

* Load an RSA private key from a file:
lnSuccess = loKey.LoadAnyFormatFile("rsaPrivateKey.key","")
IF (lnSuccess <> 1) THEN
    ? loKey.LastErrorText
    RELEASE loRsa
    RELEASE loKey
    CANCEL
ENDIF

* Get the key as XML:

lcKeyXml = loKey.GetXml()

* We'll encrypt with the public key and decrypt with the private
* key.  (It's also possible to do the reverse.)
* Note: An RSA private key is composed of different parts internally: modulus, exponent, P, Q, etc.
* An RSA public-key is a sub-set of the private key.
* Therefore, when you have a private key, you really have
* both public and private keys.
lnSuccess = loRsa.ImportPublicKey(lcKeyXml)
IF (lnSuccess <> 1) THEN
    ? loRsa.LastErrorText
    RELEASE loRsa
    RELEASE loKey
    CANCEL
ENDIF

* Encrypt a VISA credit card number:
* 1234-5678-0000-9999
lcCcNumber = "1234567800009999"

lnUsePrivateKey = 0
loRsa.EncodingMode = "base64"
lcEncryptedStr = loRsa.EncryptStringENC(lcCcNumber,lnUsePrivateKey)
? "Encrypted:"
? lcEncryptedStr

* Now decrypt:
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Rsa')
loRsaDecryptor = CreateObject('Chilkat.Rsa')

loRsaDecryptor.EncodingMode = "base64"
lnSuccess = loRsaDecryptor.ImportPrivateKey(lcKeyXml)

lnUsePrivateKey = 1
lcDecryptedStr = loRsaDecryptor.DecryptStringENC(lcEncryptedStr,lnUsePrivateKey)

? "Decrypted:"
? lcDecryptedStr

* 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

RELEASE loRsa
RELEASE loKey
RELEASE loRsaDecryptor