(Visual FoxPro) Encrypt a file to a PKCS7 encrypted message using multiple certificates from different users

Demonstrates how to encrypt a file to a PKCS7 encrypted message using multiple certificates from different users. Any one of the users can decrypt using his/her own certificate + private key.

Note: When doing public key encryption, it is the public key that is used to encrypt. The private key is required for decryption.

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

LOCAL loCrypt
LOCAL loCert1
LOCAL lnSuccess
LOCAL loCert2
LOCAL loCert3
LOCAL loFileData

* This example requires the Chilkat Crypt API to have been previously unlocked.
* See Unlock Chilkat Crypt for sample code.

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Crypt2')
loCrypt = CreateObject('Chilkat.Crypt2')

* Tell the crypt object to use 3 certificates.
* Do this by calling AddEncryptCert for each certificate.

* Load a digital certificate. 
* We don't need the private key for encryption.
* Only the public key is needed (which is included in a certificate).
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Cert')
loCert1 = CreateObject('Chilkat.Cert')
lnSuccess = loCert1.LoadFromFile("qa_data/user1/cert_user1.pem")
* Assume success for the example, but make sure your application checks for success/failure...
loCrypt.AddEncryptCert(loCert1)

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Cert')
loCert2 = CreateObject('Chilkat.Cert')
lnSuccess = loCert2.LoadFromFile("qa_data/user2/cert_user2.pem")
loCrypt.AddEncryptCert(loCert2)

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Cert')
loCert3 = CreateObject('Chilkat.Cert')
lnSuccess = loCert3.LoadFromFile("qa_data/user3/cert_user3.pem")
loCrypt.AddEncryptCert(loCert3)

* Indicate that we want PKI encryption (i.e. public-key infrastructure)
* to produce a CMS message (Cryptographic Message Syntax/PKCS7),
* that is be created with RSAES-OAEP padding, SHA256, and AES-128 for the
* bulk encryption.
loCrypt.CryptAlgorithm = "pki"
loCrypt.Pkcs7CryptAlg = "aes"
loCrypt.KeyLength = 128
loCrypt.OaepHash = "sha256"
loCrypt.OaepPadding = 1

* Load the file to be encrypted...
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loFileData = CreateObject('Chilkat.BinData')
lnSuccess = loFileData.LoadFile("qa_data/jpg/penguins.jpg")
* Your app should check for success/failure..

* Encrypt the data.  The contents of the fileData object are replaced with the PKCS7 encrypted message.
lnSuccess = loCrypt.EncryptBd(loFileData)
IF (lnSuccess <> 1) THEN
    ? loCrypt.LastErrorText
    RELEASE loCrypt
    RELEASE loCert1
    RELEASE loCert2
    RELEASE loCert3
    RELEASE loFileData
    CANCEL
ENDIF

* Save the PKCS7 encrypted message to a file..
lnSuccess = loFileData.WriteFile("qa_output/pkcs7_encrypted.p7")

* Now indicate that the PKCS7 output is to be returned in the base64 encoding.
loCrypt.EncodingMode = "base64"

? "OK."

RELEASE loCrypt
RELEASE loCert1
RELEASE loCert2
RELEASE loCert3
RELEASE loFileData